The Danish National Birth Cohort--its background, structure and aim

Maternal asthma in pregnancy and pubertal timing in daughters and sons: A population-based cohort study

PURPOSE

We investigated the impact of maternal asthma on children's pubertal timing as it remains underexplored.

METHODS

The Danish National Birth Cohort (DNBC) provided information on maternal asthma during pregnancy, supplemented with diagnosis codes from the Danish National Patient Register. The DNBC sub-cohort the Puberty Cohort gave half-yearly information on pubertal timing from 11 years. We estimated adjusted mean age differences in months for reaching Tanner Stages 1-5 for breast, genital and pubic hair development, axillary hair, acne, and voice break, and menarche for daughters, and first ejaculation for sons. Further, a negative control analysis explored confounding, and two mediation analyses explored mediation through birthweight and childhood asthma.

RESULTS

In total, 15,819 children and their mothers participated and 6.6 % of the children had mothers with asthma. Results indicated slightly later pubertal development in sons of mothers with asthma (average difference: 1.0 months (95 % confidence intervals -0.4, 2.4)). This association was not mediated by birthweight or childhood asthma. We did not observe any associations among daughters. The negative control analysis suggested some confounding towards the null.

CONCLUSION

Sons of mothers with asthma during pregnancy had slightly later pubertal timing, though the result could also indicate no association.

Ambient air pollution and childhood obesity from infancy to late childhood: An individual participant data meta-analysis of 10 European birth cohorts

Ambient air pollution may contribute to childhood obesity through various mechanisms. However, few longitudinal studies examined the relationship between pre- and postnatal exposure to air pollution and obesity outcomes in childhood. We aimed to investigate the association between pre- and postnatal exposure to air pollution and body mass index (BMI) and the risk of overweight/obesity throughout childhood in European cohorts. This study included mother-child pairs from 10 European birth cohorts (n = 37111 (prenatal), 33860 (postnatal)). Exposure to nitrogen dioxide (NO2) and fine particulate matter with aerodynamic diameter < 2.5 µm (PM2.5) was estimated at the home addresses during pre- and postnatal periods (year prior outcome assessment). BMI z-scores (continuous) and overweight/obesity status (categorical: zBMI≥+2 (<5 years) or ≥+1 (≥5 years) standard deviations) were derived at 0-2, 2-5, 5-9, 9-12 years. Associations between air pollution exposure and zBMI were estimated separately for each pollutant and cohort using linear and logistic longitudinal mixed effects models, followed by a random-effects meta-analysis. The overweight/obesity prevalence ranged from 12.3-40.5 % between cohorts at 0-2 years, 16.7-35.3 % at 2-5 years, 12.5-40.7 % at 5-9 years, and 10.7-43.8 % at 9-12 years. Results showed no robust associations between NO2 exposure and zBMI or overweight/obesity risk. Exposure to PM2.5 during pregnancy was associated with 23 % (95%CI 1.05;1.37) higher overweight/obesity risk across childhood, and higher zBMI and overweight/obesity risk at 9-12 years. Heterogeneity between cohorts was considerable (I2:25-89 %), with some cohort-specific associations; e.g., pre- and postnatal exposure to PM2.5 was associated with lower zBMI across age periods in UK cohorts (ALSPAC and BiB), while postnatal exposure to PM2.5 and NO2 was associated with higher zBMI in one Dutch cohort (Generation R). Overall, this large-scale meta-analysis suggests that prenatal PM2.5 exposure may be associated with adverse childhood obesity outcomes, but provides no evidence to support an effect of postnatal air pollution exposure, although cohort-specific associations were observed.

Demographic and socioeconomic characteristics of the women invited to the COVIDPregDK cohort: a non-response analysis

Aim: This study aimed to examine the demographic characteristics associated with participation in the COVIDPregDK cohort, aiming to identify potential sources of selection bias. Methods: In this nationwide register-based cohort study, data were used from the COVIDPregDK study, which encompasses a cohort of pregnant women from 2020 and linked them to data from the Danish registries. A comparison between women responding and those who did not respond to the questionnaire was conducted to assess their demographic and socioeconomic characteristics. The associations between respondents and various characteristics were analysed using logistic regression models. Results: The questionnaire garnered a response rate of 60%, with participation from 17,047 pregnant women and non-participation from 11,577. Respondent women were most often 30-34 years of age, of Danish origin, highly educated, and had the highest family income than non-respondents. Additionally, women above 35 years represented the most decisive risk factor of responding (35-39: odds ratio (OR) 1.17 (95% confidence interval (CI) 1.08-1.27); 40+: OR 1.27 95% CI 1.10-1.48)). Characteristics of non-respondents: families with three or more children (OR 0.55 (95% CI 0.47-0.64)); immigrants (OR 0.38 (95% CI 0.35-0.40)) and descendants (OR 0.39 (95% CI 0.34-0.45)); low educated (OR 0.40 (95% CI 0.36-0.44)) and low income (OR 0.67 (95% CI 0.61-0.72)). Conclusions: This study found significant demographic and socioeconomic disparities between respondent and non-respondent pregnant women in the COVIDPregDK study, indicating higher participation from women with higher socioeconomic status. Despite the societal lockdown during COVID-19, the lockdown did not mitigate the pre-existing factors hindering women with low socioeconomic status from engaging in research.

Maternal genetic risk factors for spontaneous preterm birth: A systematic review and meta-analysis

BACKGROUND

Despite various genomic approaches used in prior studies investigating the association of maternal genetic variability with spontaneous preterm birth (sPTB), results show inconsistency and contradictions.

OBJECTIVES

To conduct a systematic review of studies analyzing the association between maternal genetic variants and sPTB, evaluate retrieved studies based on selection criteria, classify studies into hypothesis-based and hypothesis-free, and perform a meta-analysis to identify the strongest associations.

SEARCH STRATEGY

PubMed, Scopus, and reference lists were searched until October 2024.

SELECTION CRITERIA

English-language, case-control, cross-sectional, and prospective cohort studies examining the association between maternal genetic variations and sPTB were included.

DATA COLLECTION AND ANALYSIS

Data on authors, publication year, ethnicity, genes/variants, P values, study type, sample size, inclusion criteria, and methods were collected. The association strength was estimated using odds ratios with 95% confidence intervals.

RESULTS

Eighty-one studies met eligibility criteria: 73 utilized a hypothesis-based and 14 a hypothesis-free approach. Thirty-five studies qualified for a meta-analysis, revealing a significant association in tumor necrosis factor α (rs1800629) gene for alleles and additive and recessive genetic models (P ≤ 0.05). From the hypothesis-free approach, 13 genes reached global significance in association with sPTB (P < 5 × 10-8).

CONCLUSIONS

No single gene or variant was consistently associated with sPTB risk among studies. Hypothesis-based analyses highlighted tumor necrosis factor α (rs1800629) as a modest signal, while hypothesis-free approaches identified 13 genes with genome-wide significance, pointing to new research directions in understanding sPTB genetics.

Prevalence of Painful Temporomandibular Disorders and Overlapping Primary Headaches Among Young Adults

BACKGROUND

Large population-based estimates of the prevalence of painful temporomandibular disorders (p-TMD) utilising standardised screening tools are scarce and have not investigated the prevalence of overlapping primary headaches. We aimed to estimate the prevalence of p-TMD in a large population of young adults (18 to 23 years) and to estimate the co-occurrence of p-TMD and two primary headaches, migraine and tension-type headache (TTH). The study also aimed to examine the extent of psychological (PHQ-4) and physical (PHQ-15) comorbidities and report prevalence across three gender categories (women, men and other).

METHODS

Survey data from the Danish National Birth Cohort were collected (n = 11,982), in a cross-sectional observational design. A sensitivity analysis was conducted to address participation bias, revealing minimal impact on the estimates.

RESULTS

The overall prevalence of p-TMD was 26.4% with gender-specific prevalence of women: 31.5%, other: 39.2% and men: 16.8%. Among those with p-TMD, 80.5% reported headaches at least once a month, and 13.8% over 15 days monthly. For the p-TMD individuals with a medical headache diagnosis, 31.9% experienced TTH and 10.9% migraine. The study also identified a higher proportion of moderate/severe psychological distress and physical symptoms in the p-TMD group compared to the non-p-TMD group. Logistic regression revealed a positive association between PHQ-4 and p-TMD, modified by gender (p = 0.016).

CONCLUSIONS

High overall prevalence of p-TMD and overlapping primary headaches was found in young adults. In addition, the study reports gender-specific associations between p-TMD, psychological distress and physical comorbidities indicating that this association is stronger for men than for women.

SIGNIFICANCE STATEMENT

This study found a higher-than-expected prevalence of painful temporomandibular disorders in young adults. It is based on a large population cohort and used standardised and validated screening tools. The study also reported common co-occurrence of primary headaches and explored gender differences. The study raises awareness for a possibly underestimated health burden in young individuals, particularly among individuals experiencing psychological distress and multiple physical symptoms.

Early-life growth and emotional, behavior and cognitive outcomes in childhood and adolescence in the EU child cohort network: individual participant data meta-analysis of over 109,000 individuals

Background

Fetal and infant development might be critical for cognitive outcomes and psychopathology later in life. We assessed the associations of birth characteristics and early life growth with behavior and cognitive outcomes from childhood to adolescence.

Methods

We used harmonized data of 109,481 children from 8 European birth cohorts. Birth weight, gestational age, and body mass index (BMI) tertiles at the age of 2 years were used as the exposure variables. Outcomes included internalizing and externalizing problems and attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and non-verbal intelligence quotient (Non-verbal IQ) in childhood (4-10 years), early adolescence (11-16 years), and late adolescence (17-20 years). We used 1-stage individual participant data meta-analyses using generalized linear models.

Findings

A one-week older gestational age was associated with lower scores for internalizing problems (difference -0·48 (95% CI: -0·59, -0·37)), externalizing problems (difference -0·34 (95% CI: -0·44, -0·23)), and ADHD symptoms (difference -0·38 (95% CI: -0·49, -0·27)), and with higher scores for non-verbal IQ (difference 0·65 (95% CI: 0·41, 0·89)). As compared to term birth, preterm birth was associated with higher internalizing problems (difference 3·43 (95% CI: 2·52, 4·33)) and externalizing problems (difference 2·31 (95% CI: 1·16, 3·46)), ADHD symptoms (difference 4·15 (95% CI: 3·15, 5·16)), ASD symptoms (difference 3·23 (95% CI: 0·37, 6·08)), and lower non-verbal IQ (difference -5·44 (95% CI: -7·44, -3·44)). Small size for gestational age at birth (SGA) in comparison with appropriate size for gestational age (AGA) was associated with higher ADHD symptoms (difference 4·88 (95% CI: 3·87, 5·90)) and lower Non-verbal IQ (difference -7·02 (95% CI: -8·84, -5·21)). Large size for gestational age at birth was associated with lower ADHD symptoms (difference -1·09 (95% CI: -1·73, 0·45)) and higher non-verbal IQ (difference 2·47 (95% CI: 0·77, 4·18)). Explorative analyses showed that as compared to children with an appropriate size for gestational age at birth and a normal BMI at the age of 2 years, children born SGA who remained small at 2 years had the lowest non-verbal IQ score (difference -8·14 percentiles (95% CI: -11·89, -4·39)).

Interpretation

Both fetal and early childhood growth are associated with emotional, behavioral and cognitive outcomes throughout childhood and adolescence. Compensatory infant growth might partly attenuate the adverse effects of suboptimal fetal growth. Future studies are needed to identify the potential for optimizing mental health outcomes in new generations by improving early-life growth.

Funding

This project received funding from the European Union's Horizon 2020 research and innovation programme (LIFECYCLE, grant agreement No 733206, 2016; EUCAN-Connect grant agreement No 824989; ATHLETE, grant agreement No 874583).

Is poor dietary quality in adolescence a risk factor for painful temporomandibular disorders and headaches in young adulthood? A prospective study in the Danish National Birth Cohort

OBJECTIVE

To investigate the association between adolescents' dietary quality and the presence of painful temporomandibular disorder (p-TMD) and headaches in young adulthood.

BACKGROUND

P-TMD is a common orofacial pain condition often associated with headaches and discomfort. Some studies have shown that dietary behaviors can impact chronic musculoskeletal pain. Although various factors such as sex, age, psychosocial aspects, and pain sensitivity contribute to p-TMD, the role of nutrition remains unclear.

METHODS

The dietary quality of 32,247 singletons from the Danish National Birth Cohort (DNBC) at age 14 was assessed using the Healthy Eating Index (HEI) encompassing eight domains. Among these, 11,982 (37.1%) individuals completed the TMD pain screener and headache-related queries at age 18 and above. HEI and dietary domains were analyzed as potential risk factors for p-TMD and headaches.

RESULTS

P-TMD was present in 3163 of the 11,982 members of the study population. HEI scores were divided into quartiles, with quartile four indicating the highest dietary quality. Quartile four showed a higher odds ratio (OR) for p-TMD than quartile one (OR = 1.14 [95% confidence interval (CI), 1.01-1.29]), but the significance was lost after adjustment for confounders (adjusted OR [aOR] = 1.12 [95% CI, 0.97-1.30]). Overall dietary quality was not significantly associated with headaches. However, specific dietary quality domains, such as dietary fibers (aOR = 0.97 [95% CI, 0.95-0.99]), fish (aOR = 0.98 [95% CI, 0.97-1.00]), sodium (aOR = 1.03 [95% CI, 1.01-1.06]), and added sugar (aOR = 0.97 [95% CI, 0.95-0.99]) were associated with headaches but not with p-TMD after adjustment.

CONCLUSION

Overall adolescent dietary quality did not significantly associate with p-TMD or headaches in young adulthood after adjusting for confounders. However, specific dietary domains exhibited weak but statistically significant associations with headaches. These findings underscore the interplay between diet and pain, calling for further research to unveil the underlying pathophysiological mechanisms connecting lifestyle, p-TMD, and headaches.

Season of birth and variations in male reproductive health: A population-based cohort study

BACKGROUND

Season of birth has been associated with various later reproductive health outcomes in women, but little is known on the potential associations in men.

OBJECTIVES

To investigate the association between season of birth and semen characteristics, testes volume and reproductive hormone levels in young men.

MATERIALS AND METHODS

We conducted a follow-up study of 1058 young men, born 1998 to 2000, from the Fetal Programming of Semen Quality (FEPOS) cohort, Denmark, 2017-2019. Information on season of birth was obtained from the Danish Civil Registration System, and information on male reproductive health outcomes was obtained at a clinical examination, where the men provided a semen and a blood sample and measured testes volume. Percentage differences in semen characteristics, testes volume and reproductive hormone levels were calculated according to season of birth (binary (main analysis): summer; winter and categorised by four calendar seasons and by calendar month (subanalyses)) using adjusted regression models and visualisalised according to month of birth.

RESULTS

Testosterone levels were lower (-3% (95% CI: -7%; 0%)) and oestradiol levels were higher (10% (95% CI: 2%; 20%)) in men born during the winter half-year than the summer half-year. The finding of higher oestradiol in men born during the winter was corroborated in analyses of calendar season and month of birth. Other reproductive health outcomes displayed some variation; however, estimates were generally close to null.

DISCUSSION

Although oestradiol levels seemed higher in men born during the winter half-year, this could be a chance finding. Since pregnancies usually span three seasons, this finding could therefore also reflect an association between early pregnancy during the summer and oestradiol levels.

CONCLUSION

We observed higher oestradiol levels in men born during the winter than during the summer half-year. For the remaining reproductive health outcomes, the observed fluctuations may reflect random variation.

Maternal protein intake during pregnancy and obesity risk in mothers and offspring: a prospective cohort study

BACKGROUND

The optimal dietary macronutrient composition during pregnancy to mitigate obesity risk in mothers and offspring remains unclear.

OBJECTIVES

This study aims to assess associations between maternal dietary macronutrient composition and obesity outcomes in mothers and offspring.

METHODS

We analyzed 66,360 singleton pregnancies from the Danish National Birth Cohort, with dietary intake assessed at gestational week 25. Outcomes included maternal postpartum weight retention (PPWR) at 6 and 18 mo and offspring's birth weight, risks of small for gestational age (SGA) and large for gestational age (LGA), body mass index (BMI) z-scores, and overweight/obesity (OWOB) risk at ages 7, 11, and 14 y. Mixture models with response surface visualization examined interactive macronutrient associations, and mixed restricted cubic splines assessed potential nonlinear relationships between maternal protein intake and obesity outcomes.

RESULTS

Mean maternal macronutrient compositions were 15.2% protein, 30.2% fat, and 54.1% carbohydrate. Response surfaces revealed that maternal lower protein intake (%), diluted by higher fat and/or carbohydrate, was associated with higher maternal PPWR at 6 and 18 mo but lower birth weight and BMI z-scores in offspring at ages 7, 11, and 14 y. Mixed restricted cubic splines indicated nonlinear associations between maternal protein intake (%) and SGA risk (nonlinear P = 0.003) and LGA (nonlinear P = 0.04), with a threshold around 15% protein; below this, SGA risk increased whereas LGA risk decreased. Linear associations were observed for risks of substantial PPWR (PPWR >5 kg) and childhood OWOB risk (nonlinear P > 0.05). Each 5% higher protein intake during pregnancy was related to a lower risk of substantial PPWR at 6 mo (odds ratio: 0.90; 95% confidence interval: 0.85, 0.95) and 18 mo (0.88; 0.82, 0.94) but higher risks of OWOB at ages 7 y (1.07; 1.01, 1.15) and 11 y (1.11; 1.03, 1.18), with no association at 14 y (1.02; 0.95, 1.10).

CONCLUSIONS

Higher maternal protein intake during pregnancy was associated with lower PPWR and SGA risk but higher LGA and childhood OWOB risks, highlighting potential trade-offs in maternal and offspring obesity outcomes.

Atopic dermatitis in childhood and pubertal development: A nationwide cohort study

Background

Atopic dermatitis (AD) might delay puberty, but research is lacking.

Objective

To investigate the association between AD and puberty.

Methods

A subcohort within the Danish National Birth Cohort includes children born between 2000 and 2003, with mothers reporting doctor-diagnosed AD at 6 months, 18 months, and 7 years old. The National Patient Registry identified hospital-diagnosed AD. From 11 years, the children give half-yearly information on pubertal development. We estimated the mean age difference in months at attaining Tanner stages 1 to 5 and the development of axillary hair, acne, first ejaculation, voice break, and age at menarche, using an interval-censored regression model.

Results

In total, 15,534 children participated, 21.5% had self-reported doctor-diagnosed AD and 0.7% had hospital-diagnosed AD. For girls with self-reported doctor-diagnosed AD, the average age difference at reaching all pubertal milestones was 0.0 months (95% confidence interval [CI]: -0.8; 0.8), and for hospital-diagnosed AD, it was -0.3 months (95% CI: -5.4; 4.8). For boys, the average age difference was 0.1 months (95% CI: -0.6; 0.9) and -0.3 months (95% CI: -3.6; 3.0), respectively.

Limitations

No information on treatment was available. Missing data on covariates (<5%) were not addressed.

Conclusion

No association was found between AD and puberty in either girls or boys.

A western dietary pattern during pregnancy is associated with neurodevelopmental disorders in childhood and adolescence

Despite the high prevalence of neurodevelopmental disorders, the influence of maternal diet during pregnancy on child neurodevelopment remains understudied. Here we show that a western dietary pattern during pregnancy is associated with child neurodevelopmental disorders. We analyse self-reported maternal dietary patterns at 24 weeks of pregnancy and clinically evaluated neurodevelopmental disorders at 10 years of age in the COPSAC2010 cohort (n = 508). We find significant associations with attention-deficit hyperactivity disorder (ADHD) and autism diagnoses. We validate the ADHD findings in three large, independent mother-child cohorts (n = 59,725, n = 656 and n = 348) through self-reported dietary modelling, maternal blood metabolomics and foetal blood metabolomics. Metabolome analyses identify 15 mediating metabolites in pregnancy that improve ADHD prediction. Longitudinal blood metabolome analyses, incorporating five time points per cohort in two independent cohorts, reveal that associations between western dietary pattern metabolite scores and neurodevelopmental outcomes are consistently significant in early-mid-pregnancy. These findings highlight the potential for targeted prenatal dietary interventions to prevent neurodevelopmental disorders and emphasise the importance of early intervention.

Parental Perceptions of Early Childhood In-Home Research with Monitoring: A Qualitative Study

OBJECTIVE

To explore perceptions, concerns, and enthusiasm from a diverse group of parents regarding early childhood research that involves home monitoring technologies for collecting environmental exposure data.

STUDY DESIGN

A diverse group of new and expecting parents participated in semi-structured interviews. A single interviewer conducted all sessions and introduced a hypothetical longitudinal early childhood research study, which included the following novel home monitoring approaches: (1) wearable devices, (2) audio monitoring, and (3) environmental sampling. Interviews were audio-recorded, transcribed, and coded. Qualitative description guided the study, and a constant comparative approach was used to identify themes from transcripts.

RESULTS

Twenty-four interviews were completed. Emerging themes included the following: (1) Ready and Willing to Participate; (2) Helping Others, Helping Ourselves: Motivation for Participation; (3) Trust and Transparency: Understanding the "What?" and the "Why?;" (4) Data Privacy and Security: "What If It Gets into the Wrong Hands?;" and (5) It's a Lot to Juggle: Logistical Realities. Perceptions were similar across racial, ethnic, and socioeconomic groups. Perceptions were positive, and participants desired additional information about study feasibility and purpose. Many had concerns related to wearable device safety and data privacy; a trusting relationship with the research team was a priority.

CONCLUSION

Participants had positive sentiments regarding longitudinal observational studies involving pregnancy and infancy yet expressed concerns about safety, privacy, feasibility, and transparency. These findings can inform future early childhood research study design to ensure protocols are transparent, inclusive, and appealing to parents.

Haplotype-based analysis distinguishes maternal-fetal genetic contribution to pregnancy-related outcomes

Genotype-based approaches for the estimation of SNP-based narrow-sense heritability ([Formula: see text]) have limited utility in pregnancy-related outcomes due to confounding by the shared alleles between mother and child. Here, we propose a haplotype-based approach to estimate the genetic variance attributable to three haplotypes - maternal transmitted ([Formula: see text]), maternal non-transmitted ([Formula: see text]) and paternal transmitted ([Formula: see text]) in mother-child pairs. We show through extensive simulations that our haplotype-based approach outperforms the conventional and contemporary approaches for resolving the contribution of maternal and fetal effects, particularly when m1 and p1 have different effects in the offspring. We apply this approach to estimate the explicit and relative maternal-fetal genetic contribution to the phenotypic variance of gestational duration and gestational duration-adjusted fetal size measurements at birth in 10,375 mother-child pairs. The results reveal that variance of gestational duration is mainly attributable to m1 and m2 ([Formula: see text]). In contrast, variance of fetal size measurements at birth are mainly attributable to m1 and p1 ([Formula: see text]). Our results suggest that gestational duration and fetal size measurements are primarily genetically determined by the maternal and fetal genomes, respectively. In addition, a greater contribution of m1 as compared to m2 and p1 ([Formula: see text]) to birth length and head circumference suggests a substantial influence of correlated maternal-fetal genetic effects on these traits. Our newly developed approach provides a direct and robust alternative for resolving explicit maternal and fetal genetic contributions to the phenotypic variance of pregnancy-related outcomes.

Parental occupational exposure to anticancer drugs and radiation: Risk of fetal loss and physical abnormalities in The Japan Environment and Children's Study

BACKGROUND

Many studies have indicated an association between maternal occupational exposure to hazardous agents, such as anticancer drugs and ionizing radiation, and an increased risk of adverse pregnancy outcomes, including stillbirths or miscarriages and physical abnormalities in offspring. However, the effects of recent advancements in protective measures to reduce these risks have not been clarified. Aim To investigate the current impact of parental occupational exposure to anticancer drugs and ionizing radiation on stillbirths or miscarriages as well as physical abnormalities under the circumstances of the developed safety protocols.

METHODS

This cohort study utilized The Japan Environment and Children's Study dataset, which included 96,606 fetuses born between January 2011 and March 2014. This study focused on the association between occupational exposure to these agents during pregnancy and the incidence of stillbirths or miscarriages and physical abnormalities in offspring, employing Poisson regression models for adjusted relative risk.

RESULTS

From the study population, 471 cases of stillbirths or miscarriages and 4493 infants with physical abnormalities were identified. Fisher's exact tests indicated no significant differences in fetal loss or physical abnormalities between the exposure groups. A multivariable analysis also found no significant association between maternal exposure to anticancer drugs and ionizing radiation and these adverse outcomes.

CONCLUSION

Under improved safety measures, maternal occupational exposure to anticancer drugs and ionizing radiation does not significantly affect the occurrence of stillbirths or miscarriages and physical abnormalities in offspring. These findings highlight the critical role of current safety practices and indicate lower reproductive risks with proper precautions.

Acetaminophen in Pregnancy and Attention-Deficit and Hyperactivity Disorder and Autism Spectrum Disorder

Acetaminophen is a common over-the-counter medication that recently gained substantial media attention regarding its use by pregnant individuals. In this clinical perspective, we discuss the strengths and limitations of the published literature on the effect of maternal acetaminophen use in pregnancy on the child's risk of developing attention-deficit and hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Studies included were specifically selected on the basis of the quality and validity of ADHD or ASD outcome definitions. From a total of 56 identified studies, commentaries, and editorials of relevance, we critically reviewed nine studies with original data that satisfied our inclusion criteria and three meta-analyses. Most studies that have reported positive findings are difficult to interpret because they have important biases, notably a high degree of selection bias, variability in selection and adjustment for various potential confounders, and unmeasured familial confounding. When unobserved familial confounding through sibling analysis was controlled for, associations weakened substantially. This suggests that residual confounding from shared genetic and environmental factors may have caused an upward bias in the original observations. According to the current scientific evidence, in utero exposure to acetaminophen is unlikely to confer a clinically important increased risk of childhood ADHD or ASD. The current level of evidence does not warrant changes to clinical guidelines on the treatment of fever or pain in pregnancy. Prospective research designed to account for familial and psychosocial environmental factors related to both maternal use of acetaminophen and children's neurodevelopment should be undertaken.

The iceberg model of suicidal ideation and behaviour in Danish adolescents: integration of national registry and self-reported data within a national birth cohort

Hospital records are used to identify suicide attempts in many countries but not all individuals present to hospital after a suicide attempt i.e., suggesting a 'hidden number'. Our aim was to present the prevalence of suicide ideation, plans, attempts, and suicides among Danish adolescents, including attempts not resulting in hospital contact. The study population consisted of participants in the Danish National Birth Cohort participating in an 18-year follow-up, with individual-level linkage to national register data. Prevalence was estimated with a variable with mutually exclusive categories ranging from no suicidality to self-reported suicide ideation, -plans, -attempt and hospital-recorded suicide attempt and stratified on sex and parental income. The 'hidden number' was estimated as the ratio between suicide attempts with and without hospital contact. Among 47 858 participants, all aged 18-years, 36% girls and 28% boys reported suicide ideation at least once in their life. In addition, 6% girls and 3% boys had either reported or been recorded with a suicide attempt. For every attempt recorded in the hospital setting, two girls (ratio, 1:2) and six boys (ratio, 1:6) reported having attempted suicide without hospital contact. The prevalence of any suicide attempt was 8% and 3% in the lowest and highest income group, respectively. Before age 18, 0·011% girls and 0·016% boys had died by suicide. In conclusion, suicidal ideation and behaviour are common in adolescents and there is a substantial 'hidden number' of adolescents with suicide attempt. These results emphasize the need for early age suicide preventive interventions in community-settings e.g., school environments.

Is maternal diabetes during pregnancy associated with neurodevelopmental, cognitive and behavioural outcomes in children? Insights from individual participant data meta-analysis in ten birth cohorts

BACKGROUND

Growing evidence shows that dysregulated metabolic intrauterine environments can affect offspring's neurodevelopment and behaviour. However, the results of individual cohort studies have been inconsistent. We aimed to investigate the association between maternal diabetes before pregnancy and gestational diabetes mellitus (GDM) with neurodevelopmental, cognitive and behavioural outcomes in children.

METHODS

Harmonised data from > 200 000 mother-child pairs across ten birth cohorts in Europe and Australia were available. Mother-child pairs were included for analysis to determine whether GDM was recorded (yes or no) and whether at least one neurodevelopmental, cognitive and behavioural outcome was available in children aged 3 to 13 years. Confounder-adjusted regression models were used to estimate associations between maternal diabetes and child outcomes using two-stage individual participant data (IPD) meta-analysis. Model 1 included a crude estimate. The full adjustment model (model 2) included adjustment for child sex, maternal age, pre-pregnancy BMI, pregnancy weight gain, maternal smoking during pregnancy, plurality, parity and maternal education.

RESULTS

Children (aged 7-10 years) born to mothers with GDM had higher attention-deficient hyperactive disorder (ADHD) symptoms compared to non-exposed controls (model 2, regression coefficient (β) 3.67 (95% CI 1.13, 6.20), P = 0.001). Moreover, children (aged 4-6 years) born to mothers with GDM exhibited more externalising problems than those born to mothers without GDM (model 2, β 2.77 (95% CI 0.52, 5.02), P = 0.01). A pre-existing maternal history of type 1 and type 2 diabetes mellitus was associated with ADHD symptoms at 4-6 years (model 1, β 8.82 (95% CI 2.21, 15.45, P = 0.009) and β 7.90 (95% CI 0.82, 14.98, P = 0.02), respectively). The association was no longer apparent in further adjustments.

CONCLUSIONS

This study found that children between 4 - 6 and 7-10 years of age born to mothers with GDM have a greater likelihood of developing externalising problems and ADHD symptoms, respectively. Externalising problems often co-exist with ADHD symptoms and precede formal ADHD diagnosis. Overall, this large-scale multi-cohort study suggested that a dysregulated metabolic environment during pregnancy may contribute to ADHD symptoms and externalising problems in young children.

Self-rated health in preadolescent children as a predictor for hospital contacts and redeemed prescriptions: the Danish National Birth Cohort 1996-2002

AIM

The decline in self-rated health among young people raises concerns for future health outcomes. We examined whether self-rated health in preadolescence predicts hospital contacts and prescription redemption in later adolescence.

METHODS

This longitudinal study uses the Danish National Birth Cohort on children born 1996-2002. A questionnaire was distributed to 96,382 11-year-old preadolescents followed from 2010 to 2018. Number of hospital contacts and prescriptions were obtained from Danish registers. Incidence rate ratios (IRRs) were estimated, comparing preadolescents with poor ('Not So Good'/'Poor') and 'Good' self-rated health to those with 'Excellent' self-rated health.

RESULTS

Among the 47,365 (49.1%) 11-year-old participants, 5.3% reported poor self-rated health and 38.3% reported good health. Analyses revealed that children with good self-rated health had higher rates of somatic (IRR, 1.17 [1.14-1.21]) and psychiatric (IRR, 1.63 [1.47-1.81]) hospital contacts. Children with poor self-rated health showed even higher rates, with IRRs of 1.73 [1.62-1.85] for somatic and 3.54 [3.03-4.15] for psychiatric contacts. Additionally, those with good self-rated health had more somatic and psychiatric prescriptions (IRR, 1.25 [1.21-1.30] and 1.75 [1.55-1.97], respectively), whereas children with poor self-rated health had IRRs of 1.67 [1.56-1.80] for somatic and 4.03 [3.39-4.82] for psychiatric prescriptions.

CONCLUSION

Preadolescents with both good and poor self-rated health show higher rates of hospital contacts and prescription redemption in adolescence, especially pronounced in children with poor self-rated health. This indicates that early-life health perceptions impact long-term wellbeing, particularly psychiatric health. This simple self-rated health measure provides valuable insights for healthcare professionals by aiding in identifying children in need of support and early intervention.

Paternal pre-conceptional smoking and semen quality in the adult son

BACKGROUND

Growing evidence suggests intergenerational effects of paternal pre-conceptional smoking through the germ line, but its specific impact on offspring semen quality remains uncertain because of challenges in isolating paternal exposure from maternal passive smoking or underreporting.

METHODS

We reran previous analyses estimating differences in semen parameters and testicular size according to paternal smoking in 867 young adult men, adding first-trimester maternal plasma cotinine to the original adjustment for maternal self-reported smoking. We also estimated differences in sperm DNA fragmentation. Paternal smoking was reported by the pregnant women around gestational week 16. Analyses were additionally adjusted for household occupational status, parental ages at birth, maternal pre-pregnancy body mass index and alcohol consumption, and abstinence time, and accounted for spillage, minutes from ejaculation to analysis, and son's own smoking.

RESULTS

We found no association between paternal preconceptional smoking and any of the semen parameters or testicular size. Adjustment for son's own smoking did not change results.

DISCUSSION

While maternal plasma cotinine offers an objective measure of tobacco exposure and allows for a more thorough adjustment of maternal smoking, the high correlation between paternal pre-conceptional smoking and maternal cotinine exposure may, have resulted in overadjustment removing some paternal effect. Inability to distinguish between paternal never smokers and former smokers, may have led to misclassification of paternal pre-conceptional smoking and underestimation of associations.

CONCLUSION

We found no support for an independent association between paternal pre-conceptional smoking and semen quality in young adult sons, but studies with more detailed paternal smoking history are needed before firm conclusions can be drawn.

Participant engagement and involvement in longitudinal cohort studies: qualitative insights from a selection of pregnancy and birth, twin, and family-based population cohort studies

BACKGROUND

Longitudinal cohort studies are pivotal to understand how socioeconomic, environmental, biological, and lifestyle factors influence health and disease. The added value of cohort studies increases as they accumulate life course data and expand across generations. Ensuring that participants stay motivated to contribute over decades of follow-up is, however, challenging. Participant engagement and involvement (PEI) aims to secure the long-term commitment of participants and promote researcher-participant interaction. This study explored PEI practices in a selection of pregnancy and birth, twin, and family-based population cohort studies.

METHODS

Purposive sampling was used to identify cohorts in Europe, Australia and New Zealand. Fourteen semi-structured digital interviews were conducted with cohort study representatives to explore strategies for participant recruitment, informed consent, communication of general and individual information to participants, data collection, and participant involvement. Experiences, resources allocated to PEI, and reflections on future PEI, were discussed. The interview data were analyzed using a content analysis approach and summary results were reviewed and discussed by the representatives.

RESULTS

The cohort studies used various strategies to recruit participants including support from health professionals and organizations combined with information on the studies' web sites and social media. New approaches such as intra-cohort recruitment, were being investigated. Most cohorts transitioned from paper-based to digital solutions to collect the participants' consent and data. While digital solutions increased efficiency, they also brought new challenges. The studies experimented with the use of participant advisory panels and focus groups to involve participants in making decisions, although their success varied across age and socio-economic background. Most representatives reported PEI resources to be limited and called for more human, technical, educational and financial resources to maximize the positive effects of PEI.

CONCLUSIONS

This study of PEI among well-established cohort studies underscores the importance of PEI for project sustainability and highlights key factors to consider in developing PEI. Our analysis shows that knowledge gaps exist regarding which approaches have highest impact on retention rates and are best suited for different participant groups. Research is needed to support the development of best practices for PEI as well as knowledge exchange between cohorts through network building.

Breastfeeding Duration Is Not Associated With Offspring Inflammatory Bowel Disease Risk in Three Population-Based Birth Cohorts

BACKGROUND & AIMS

Breastfeeding is critical for offspring health and development. Although many observational studies report a protective effect between breastfeeding and inflammatory bowel disease (IBD), the relationship is not well-understood.

METHODS

We used prospectively collected data from 3 population-based birth cohorts (Danish National Birth Cohort, Norwegian Mother, Father, and Child Cohort, and All Babies in Southeast Sweden) and cross-linked national registers to ascertain the impact of breastfeeding duration on offspring IBD risk in each country, using adjusted Cox proportional regression analyses. We performed meta-analyses to determine pooled estimates.

RESULTS

We included 148,737 offspring and 169,510 offspring in analyses of exclusive and any breastfeeding duration, respectively. During median follow-up of 16.3-22.3 years, between 1996 and 2021, 543 offspring were diagnosed with IBD. In each country, there was no association between exclusive breastfeeding duration and offspring IBD risk after adjusting for birth year (Denmark), offspring sex, parental IBD status, maternal education, smoking during pregnancy, age at delivery, mode of delivery, preterm birth, and small for gestational age. The pooled adjusted hazard ratio for IBD was 1.24 (95% confidence interval, 0.94-1.62; Q = 0.16, I2 = 0.0%) and 1.02 (95% confidence interval, 0.85-1.21; Q = 1.45, I 2= 0.0%) among offspring breastfed exclusively for ≥6 months and <4 months, respectively, compared with 4-5 months. Similarly, we found null associations in pooled analyses of any breastfeeding duration and IBD, subtypes Crohn's disease and ulcerative colitis, as well as in cohort-specific analyses.

CONCLUSIONS

In prospectively collected data from 3 population-based birth cohorts, the duration of exclusive or any breastfeeding was not associated with offspring IBD risk.

Maternal coffee consumption and biomarkers of reproductive health in young, adult sons: a cohort study

It has been proposed that poor semen quality may have its origins from fetal programming due to environmental factors. We investigated whether maternal coffee consumption during early pregnancy was associated with biomarkers of reproductive health in adult sons in the Fetal Programming of Semen Quality (FEPOS) cohort. In 2017-2019, 1058 young men provided a semen and blood sample and self-measured their testis volume. Daily maternal coffee consumption was reported by the mothers around gestational week 17. We estimated relative percentage differences with 95 % confidence intervals (CI) for semen quality measures, testis volume, and reproductive hormone levels according to maternal coffee consumption during pregnancy. Maternal coffee consumption (yes/no (reference)) was associated with lower semen volume (-7.0 % (95 % CI:-12.9;-0.7)), lower proportion of morphologically normal spermatozoa (-8.3 % (95 % CI:-16.5;0.8)), higher proportion of non-progressive and immotile spermatozoa (4.3 % (95 % CI:-1.5;10.3)), and lower testis volume (-4.8 % (95 % CI:-9.0;-0.4)). No indication of a dose-response association or threshold effects was observed in the categorized and continuous analyses. No associations with reproductive hormone levels were observed in any of the analyses. Overall, the study does not provide obvious indications that maternal coffee consumption in early pregnancy deteriorates male offspring fecundity. While some minor changes were observed, most estimates were small with confidence intervals overlapping the null. Future studies, preferably with greater exposure contrast, are warranted before a conclusion can be drawn as to whether maternal coffee consumption during pregnancy constitutes a risk for reproductive health in adult sons.

Mental health, risk behaviors, and social life factors in relation to adolescents' suicide ideation, plans and attempt

OBJECTIVE

This study investigated differences in mental health and well-being, risk behaviors, and social life factors among adolescents who experienced different forms of suicidality.

METHODS

We examined 18-years-olds in the Danish National Birth Cohort (N = 47,852). Suicidality was defined with mutually exclusive categories ranging from no suicidality, self-reported suicide ideation, plans, and attempt as well as hospital-recorded suicide attempt. The proportion of adolescents with self-reported poor mental health and well-being, risk behaviors, and social life factors were compared across forms of suicidality. Sample weights were applied.

RESULTS

Depressive symptoms were reported by 14% (95% CI 13%;14%) of girls with no suicidality, 44% (95% CI 43%;45%) of girls with suicide ideation, and 68% (95% CI 65%;72%) 66% (95% CI 60%;72%) of girls with self-reported suicide attempt or hospital-recorded suicide attempt respectively. Among boys, depressive symptoms were reported by 5% (95% CI 4%;5%) of those with no suicidality, 27% (95% CI 26%;28%) of those with suicide ideation, and 51% (95% CI 45%;57%) and 40% (95% CI 22%;58%) of those with self-reported suicide attempt or hospital-recorded suicide attempt respectively. Likewise, other aspects of poor mental health and well-being gradually increased relative with more severe forms of suicidality, while no notable differences were identified between adolescents with self-reported and hospital-recorded suicide attempt. Similar tendencies were observed for risk behaviors and social life factors.

CONCLUSION

These findings suggest that adolescents with suicidality, including the large proportion with suicide ideation only, faces challenges across several parameters of mental health and well-being, risk behavior, and social life factors. This emphasizes the need for community-based interventions to identify and support the large group of adolescents experiencing both more and less severe forms of suicidality. Clinicians should prioritize comprehensive psychiatric intervention to address the complex needs of suicidal adolescents effectively.

Maternal use of nitrosatable drugs during pregnancy and adult male reproductive health: A population-based cohort study

BACKGROUND

Prenatal exposures to xenobiotics during the masculinization programming window are suggested to impact male fecundity later in life. Frequently used nitrosatable drugs, such as penicillins and beta2-agonists, contain amines or amides that may form teratogenic compounds in reaction with nitrite.

OBJECTIVES

We explored whether maternal nitrosatable drug use during gestation was associated with biomarkers of male fecundity in adulthood; moreover, the potential modifiable effect of nitrate and vitamin intake was investigated.

METHOD

We performed a cohort study in the Fetal Programming of Semen Quality cohort that includes semen characteristics, reproductive hormone concentrations, and measures of testis size on 1058 young adult sons in the Danish National Birth Cohort. Information on maternal use of nitrosatable drugs was obtained from questionnaires and interviews around gestational weeks 11 and 16. A multivariable negative binomial regression model was used to obtain relative differences in biomarkers of male fecundity for those whose mothers used nitrosatable drugs compared to those without such maternal use. In sub-analyses, the exposure was categorized according to nitrosatable drug type: secondary amine, tertiary amine, or amide. We investigated dose dependency by examining the number of weeks with intake and explored potential effect modification by low versus high maternal nitrate and vitamin intake from diet and nitrate concentration in drinking water. We added selection weights and imputed values of missing covariates to limit the risk of selection bias.

RESULTS

In total, 19.6% of the study population were born of mothers with an intake of nitrosatable drugs at least once during early pregnancy. Relative differences in biomarkers related to male fecundity between exposed and unexposed participants were negligible. Imputation of missing covariates did not fundamentally alter the results. Furthermore, no sensitive subpopulations were detected.

CONCLUSIONS

The results suggest that maternal use of nitrosatable drugs does not have a harmful influence on the male fecundity of the offspring.

Social inequalities in child mental health trajectories: a longitudinal study using birth cohort data 12 countries

BACKGROUND

Social inequalities in child mental health are an important public health concern. Whilst previous studies have examined inequalities at a single time point, very few have used repeated measures outcome data to describe how these inequalities emerge. Our aims were to describe social inequalities in child internalising and externalising problems across multiple countries and to explore how these inequalities change as children age.

METHODS

We used longitudinal data from eight birth cohorts containing participants from twelve countries (Australia, Belgium, Denmark, France, Germany, Greece, Italy, Netherlands, Poland, Norway, Spain and the United Kingdom). The number of included children in each cohort ranged from N = 584 (Greece) to N = 73,042 (Norway), with a total sample of N = 149,604. Child socio-economic circumstances (SEC) were measured using self-reported maternal education at birth. Child mental health outcomes were internalising and externalising problems measured using either the Strengths and Difficulties Questionnaire or the Child Behavior Checklist. The number of data collection waves in each cohort ranged from two to seven, with the mean child age ranging from two to eighteen years old. We modelled the slope index of inequality (SII) using sex-stratified multi-level models.

RESULTS

For almost all cohorts, at the earliest age of measurement children born into more deprived SECs had higher internalising and externalising scores than children born to less deprived SECs. For example, in Norway at age 2 years, boys born to mothers of lower education had an estimated 0.3 (95% CI 0.3, 0.4) standard deviation higher levels of internalising problems (SII) compared to children born to mothers with high education. The exceptions were for boys in Australia (age 2) and both sexes in Greece (age 6), where we observed minimal social inequalities. In UK, Denmark and Netherlands inequalities decreased as children aged, however for other countries (France, Norway, Australia and Crete) inequalities were heterogeneous depending on child sex and outcome. For all countries except France inequalities remained at the oldest point of measurement.

CONCLUSIONS

Social inequalities in internalising and externalising problems were evident across a range of EU countries, with inequalities emerging early and generally persisting throughout childhood.

Reproductive history of parous women and urinary incontinence in midlife: A National Birth Cohort follow-up study

OBJECTIVE

To investigate how reproductive history was associated with urinary incontinence in midlife.

DESIGN

A follow-up study.

SETTING

Denmark.

POPULATION

A total of 39 977 mothers who participated in the Maternal Follow up (2013-2014) in the Danish National Birth Cohort. National registries provided their reproductive history.

METHODS

How parity, mode of birth and obstetric tears associated with urinary incontinence were estimated with adjusted odds ratios (OR) and 95% CI using logistic regression.

MAIN OUTCOME MEASURES

Self-reported urinary incontinence including subtypes stress, urge and mixed urinary incontinence.

RESULTS

At an average age of 44 years, the prevalence of any urinary incontinence was 32% (21% stress, 2% urge, and 8% mixed urinary incontinence). Women with two births more often had urinary incontinence than women with one birth (OR 1.20, 95% CI 1.10-1.31). Compared with women with only spontaneous births, a history of only caesarean sections was associated with much lower odds of urinary incontinence (OR 0.39, 95% CI 0.35-0.42) and a history of instrumental births with slightly lower odds (OR 0.92, 95% CI 0.86-0.98). Compared with no tear/first-degree tear as the largest tear, episiotomy was associated with less urinary incontinence (OR 0.91, 95% CI 0.86-0.97) whereas third/fourth-degree tears were associated with more (OR 1.14, 95% CI 1.04-1.25). Findings were mainly explained by similar associations with stress and mixed urinary incontinence.

CONCLUSIONS

Vaginal birth was associated with a higher risk of long-term urinary incontinence, but our results indicate that this risk may be reduced by shortening the second stage of birth.

Maternal stress in pregnancy and pubertal timing in girls and boys: a cohort study

OBJECTIVE

To investigate whether maternal stress in pregnancy is associated with pubertal timing in girls and boys and to explore potential mediation by childhood body mass index (BMI) and childhood psychosocial stress.

DESIGN

Cohort study.

SETTING

Not applicable.

PATIENTS

In total, 14,702 girls and boys from the Puberty Cohort, nested within the Danish National Birth Cohort.

INTERVENTION

Maternal stress was obtained from a computer-assisted telephone interview in gestational weeks 30-32 as maternal life stress and emotional distress in pregnancy using questions on the basis of validated screening tools. Maternal life stress and emotional distress in pregnancy were analyzed separately and in an interaction analysis.

MAIN OUTCOME MEASURES

Pubertal timing was measured half-yearly from age 11 years and throughout pubertal development and assessed as Tanner stages 1-5 (breast and pubic hair development in girls and genital and pubic hair development in boys), menarche in girls, voice break and first ejaculation in boys, and occurrence of acne and axillary hair in both girls and boys. A combined estimate for overall pubertal timing was derived using Huber-White robust variance estimation. Mean differences in age at attaining the pubertal milestones according to prenatal exposure to no (reference), low-, moderate-, or high-maternal stress in pregnancy were estimated using a multivariable censored regression model. Potential mediation by childhood BMI and childhood psychosocial stress was investigated in separate models.

RESULTS

After adjustment for potential confounding factors, prenatal exposure to high-maternal life stress (combined estimate: -1.8 months [95% CI, -2.7 to -0.8] and -0.9 months [95% CI, -1.8 to 0.0]), high maternal emotional distress (combined estimate: -1.5 months [95% CI, -2.5 to -0.5] and -1.7 months [95% CI, -2.8 to -0.7]), and both high-maternal life stress and emotional distress (combined estimate: -2.8 months [95% CI, -4.2, to -1.4] and -1.7 months [95% CI, -3.1 to -0.2]) were associated with earlier pubertal timing in girls and boys, respectively. The associations were not mediated by childhood BMI or childhood psychosocial stress.

CONCLUSIONS

Prenatal exposure to maternal stress in pregnancy was associated with earlier pubertal timing in girls and boys in a dose-dependent manner. The associations were not mediated by childhood BMI or childhood psychosocial stress.

Early childcare arrangements and children's internalizing and externalizing symptoms: an individual participant data meta-analysis of six prospective birth cohorts in Europe

Background

Early childcare attendance may be related to children's internalizing and externalizing symptoms throughout childhood and young adolescence, however evidence from Europe is limited. We aimed to assess this association across multiple population-based birth cohorts of children recruited in different European countries.

Methods

Data come from six parent-offspring prospective birth cohort studies across five European countries within the EU Child Cohort Network. A total of 87,208 parent-child dyads were included in the study. To test associations between childcare attendance (centre-based or informal) anytime between ages 0 and 4 years and children's internalizing and externalizing symptoms in middle childhood and young adolescence (measured at: 5-6 years, 7-9 years, and 10-13 years) a two-stage individual participant data meta-analysis was implemented. Linear regression models were performed in each cohort separately; combined random-effects meta-analysis was then used to obtain overall association estimates. In secondary analyses, we tested interactions between childcare attendance and mother's post-partum depression, low education status, and the child's sex.

Findings

Compared to children who were exclusively cared for by their parents prior to school entry, those who attended centre-based childcare had lower levels of internalizing symptoms in all age groups [5-6 years: β: -1.78 (95% CI: -3.39, -0.16); 7-9 years: β: -0.55 (95% CI: -0.88, -0.73); 10-13 years: β: -0.76 (95% CI: -1.15, -0.37)]. Children who attended informal childcare appeared to have elevated levels of internalizing symptoms between 7-9 and 10-13 years, respectively [β: 1.65 (95% CI: 1.25, 2.06); β: 1.25 (95% CI: 0.96, 1.54)]. Informal childcare attendance was also associated with increased levels of children's externalizing symptoms between 7-9 and 10-13 years, respectively [β: 2.84 (95% CI: 1.41, 4.26); β: 2.19 (95% CI: 0.54, 3.84)].

Interpretation

Early centre-based childcare is associated with decreased levels of children's internalizing symptoms compared to exclusive parental care. For informal childcare, opposite associations were observed. Overall, our results suggest that centre-based childcare attendance may be associated with slight positive impacts on children's emotional development and should be encouraged by public policies. In addition, children from socioeconomically disadvantaged families require special attention, as they may not sufficiently benefit from universal early childhood education and care (ECEC).

Funding

This research was funded by the ERC Consolidator grant RESEDA (Horizon Europe, 101001420).

Sibling relatedness and pubertal development in girls and boys: A population-based cohort study

PURPOSE

To investigate the association between sibling relatedness and pubertal development in girls and boys.

METHODS

This cohort study consisted of 10,657 children from the Puberty Cohort, Denmark. Information on sibling relatedness was obtained by self-report. Information on pubertal markers was obtained half yearly from age 11 and throughout puberty. Mean age difference at attaining pubertal markers was estimated using interval-censored regression models according to sibling relatedness (full, half and/or step siblings; half and/or step siblings; no siblings; relative to full siblings).

RESULTS

Girls with both full, half and/or step siblings (-1.2 (CI 95 %: -2.5; 0.1) months), only half- and/or stepsiblings (-2.2 (CI 95 %: -3.7; -0.7) months), and no siblings (-5.5 (CI 95 %: -8.5; -2.5) months) entered puberty earlier than girls with full siblings. Boys with full, half and/or step siblings (-1.4 (CI 95 %: -2.7; -0.1) months), only half and/or step siblings (-1.2 (CI 95 %: -3.0; 0.6) months), and no siblings (-4.5 (CI 95 %: -8.8; -0.3) months) entered puberty earlier than boys with full siblings.

CONCLUSIONS

Children with sibling relatedness other than full siblings entered puberty earlier than their peers with full siblings even after adjustment for parental cohabitation status, childhood body mass index and childhood internalizing and externalizing symptoms.

Advancing Understanding of Chemical Exposures and Maternal-child Health Through the U.S. Environmental Influences on Child Health Outcomes (ECHO) Program: A Scoping Review

PURPOSE OF REVIEW

Environmental chemical exposures may disrupt child development, with long-lasting health impacts. To date, U.S. studies of early environmental exposures have been limited in size and diversity, hindering power and generalizability. With harmonized data from over 60,000 participants representing 69 pregnancy cohorts, the National Institutes of Health's Environmental influences on Child Health Outcomes (ECHO) Program is the largest study of U.S. children's health. Here, we: (1) review ECHO-wide studies of chemical exposures and maternal-child health; and (2) outline opportunities for future research using ECHO data.

RECENT FINDINGS

As of early 2024, in addition to over 200 single-cohort (or award) papers on chemical exposures supported by ECHO, ten collaborative multi-cohort papers have been made possible by ECHO data harmonization and new data collection. Multi-cohort papers have examined prenatal exposure to per- and polyfluoroalkyl substances (PFAS), phthalates, phenols and parabens, organophosphate esters (OPEs), metals, melamine and aromatic amines, and emerging contaminants. They have primarily focused on describing patterns of maternal exposure or examining associations with maternal and infant outcomes; fewer studies have examined later child outcomes (e.g., autism) although follow up of enrolled ECHO children continues. The NICHD's Data and Specimen Hub (DASH) database houses extensive ECHO data including over 470,000 chemical assay results and complementary data on priority outcome areas (pre, peri-, and postnatal, airway, obesity, neurodevelopment, and positive health), making it a rich resource for future analyses. ECHO's extensive data repository, including biomarkers of chemical exposures, can be used to advance our understanding of environmental influences on children's health. Although few published studies have capitalized on these unique harmonized data to date, many analyses are underway with data now widely available.

The Sri Lanka Mother and Newborn Growth (S-MaNGro) Cohort: Protocol of a Nationwide Prospective Study

Perinatal cohort studies with a prospective longitudinal design are critical for determining the effects of early-life exposures on offspring's health outcomes. The Sri Lanka Mother and Newborn Growth cohort study aims to investigate the impact of maternal nutritional and psychosocial factors on newborns' birth weight in the Sri Lankan context. This paper presents the methodology of participant recruitment, follow-ups, an overview of measurements, and planned data analyses. This study included a nationally representative sample of Sri Lankan pregnant women recruited in their first trimester of pregnancy. Follow-up assessments were conducted once during the second and third trimesters of pregnancy and after the baby's birth, prospectively tracking the women's dietary intake, mental health, hemoglobin concentrations, and gestational weight gain data. Once the participants delivered their babies, the data on gestational age, sex of the newborn, birth weight, length and occipitofrontal circumference at birth, and mode of delivery were collected. Between August 2022 and August 2023, we recruited 2000 first-trimester pregnant women to the cohort and continued to follow up with them until the baby's birth. The response rates were 90.4%, 81.4%, and 75.2% in the first, second, and third follow-ups. We plan to analyze the data in July 2024. We expect this study to provide valuable insights into various early-life exposures affecting neonatal birth weight. The study's findings will serve as a valuable information resource for a broader scientific community, enabling the development of effective policies to prevent low-birth-weight deliveries in low-resource settings.

Maternal intake of paracetamol during pregnancy and biomarkers of male fecundity in young adult sons

Paracetamol is suggested to have endocrine disrupting properties possibly affecting fetal programming of reproductive health that might lead to impaired semen quality and changes in reproductive hormones. In this longitudinal study, we included 1058 young adult men born 1998-2000 into the Danish National Birth Cohort with follow-up at 18-21 years of age. The exposure, maternal intake of paracetamol, was modelled in three ways: dichotomized, trimester-specific, and as duration of exposure categorized into: short (1-2 weeks), medium (3-9 weeks) or long duration (>9 weeks) vs. no intake. Outcomes included semen characteristics, self-measured testis volume, and reproductive hormone levels. We used negative binominal regression to estimate the percentage difference and 95% confidence interval (CI) for each outcome. In total, 547 (48%) sons were prenatally exposed to paracetamol due to maternal intake at least once. Maternal intake of paracetamol during pregnancy was not associated with any of the biomarkers in the dichotomized or trimester-specific exposure models. For duration of exposure, sons of mothers with long duration of maternal intake of paracetamol showed tendencies towards lower semen concentration (-14% [95% CI: -31%; 8%]), a higher proportion of nonprogressive and immotile spermatozoa (8% [95% CI: -4%; 21%]) and higher DNA Fragmentation Index (16% [95% CI: -1%; 36%]) compared to son of mothers with no intake. Maternal intake of paracetamol during pregnancy was not clearly associated with biomarkers of male fecundity in adult sons. However, it cannot be ruled out that long duration of maternal intake of paracetamol might be associated with impaired semen characteristics.

Green spaces and respiratory, cardiometabolic, and neurodevelopmental outcomes: An individual-participant data meta-analysis of >35.000 European children

Studies evaluating the benefits and risks of green spaces on children's health are scarce. The present study aimed to examine the associations between exposure to green spaces during pregnancy and early childhood with respiratory, cardiometabolic, and neurodevelopmental outcomes in school-age children. We performed an Individual-Participant Data (IPD) meta-analysis involving 35,000 children from ten European birth cohorts across eight countries. For each participant, we calculated residential Normalized Difference Vegetation Index (NDVI) within a 300 m buffer and the linear distance to green spaces (meters) during prenatal life and childhood. Multiple harmonized health outcomes were selected: asthma and wheezing, lung function, body mass index, diastolic and systolic blood pressure, non-verbal intelligence, internalizing and externalizing problems, and ADHD symptoms. We conducted a two-stage IPD meta-analysis and evaluated effect modification by socioeconomic status (SES) and sex. Between-study heterogeneity was assessed via random-effects meta-regression. Residential surrounding green spaces in childhood, not pregnancy, was associated with improved lung function, particularly higher FEV1 (β = 0.06; 95 %CI: 0.03, 0.09 I2 = 4.03 %, p < 0.001) and FVC (β = 0.07; 95 %CI: 0.04, 0.09 I2 = 0 %, p < 0.001) with a stronger association observed in females (p < 0.001). This association remained robust after multiple testing correction and did not change notably after adjusting for ambient air pollution. Increased distance to green spaces showed an association with lower FVC (β = -0.04; 95 %CI: -0.07, -0.02, I2 = 4.8, p = 0.001), with a stronger effect in children from higher SES backgrounds (p < 0.001). No consistent associations were found between green spaces and asthma, wheezing, cardiometabolic, or neurodevelopmental outcomes, with direction of effect varying across cohorts. Wheezing and neurodevelopmental outcomes showed high between-study heterogeneity, and the age at outcome assessment was only associated with heterogeneity in internalizing problems.. This large European meta-analysis suggests that childhood exposure to green spaces may lead to better lung function. Associations with other respiratory outcomes and selected cardiometabolic and neurodevelopmental outcomes remain inconclusive.

Development and validation of prediction models for fetal growth restriction and birthweight: an individual participant data meta-analysis

Background

Fetal growth restriction is associated with perinatal morbidity and mortality. Early identification of women having at-risk fetuses can reduce perinatal adverse outcomes.

Objectives

To assess the predictive performance of existing models predicting fetal growth restriction and birthweight, and if needed, to develop and validate new multivariable models using individual participant data.

Design

Individual participant data meta-analyses of cohorts in International Prediction of Pregnancy Complications network, decision curve analysis and health economics analysis.

Participants

Pregnant women at booking. External validation of existing models (9 cohorts, 441,415 pregnancies); International Prediction of Pregnancy Complications model development and validation (4 cohorts, 237,228 pregnancies).

Predictors

Maternal clinical characteristics, biochemical and ultrasound markers.

Primary outcomes

fetal growth restriction defined as birthweight <10th centile adjusted for gestational age and with stillbirth, neonatal death or delivery before 32 weeks' gestation birthweight.

Analysis

First, we externally validated existing models using individual participant data meta-analysis. If needed, we developed and validated new International Prediction of Pregnancy Complications models using random-intercept regression models with backward elimination for variable selection and undertook internal-external cross-validation. We estimated the study-specific performance (c-statistic, calibration slope, calibration-in-the-large) for each model and pooled using random-effects meta-analysis. Heterogeneity was quantified using τ2 and 95% prediction intervals. We assessed the clinical utility of the fetal growth restriction model using decision curve analysis, and health economics analysis based on National Institute for Health and Care Excellence 2008 model.

Results

Of the 119 published models, one birthweight model (Poon) could be validated. None reported fetal growth restriction using our definition. Across all cohorts, the Poon model had good summary calibration slope of 0.93 (95% confidence interval 0.90 to 0.96) with slight overfitting, and underpredicted birthweight by 90.4 g on average (95% confidence interval 37.9 g to 142.9 g). The newly developed International Prediction of Pregnancy Complications-fetal growth restriction model included maternal age, height, parity, smoking status, ethnicity, and any history of hypertension, pre-eclampsia, previous stillbirth or small for gestational age baby and gestational age at delivery. This allowed predictions conditional on a range of assumed gestational ages at delivery. The pooled apparent c-statistic and calibration were 0.96 (95% confidence interval 0.51 to 1.0), and 0.95 (95% confidence interval 0.67 to 1.23), respectively. The model showed positive net benefit for predicted probability thresholds between 1% and 90%. In addition to the predictors in the International Prediction of Pregnancy Complications-fetal growth restriction model, the International Prediction of Pregnancy Complications-birthweight model included maternal weight, history of diabetes and mode of conception. Average calibration slope across cohorts in the internal-external cross-validation was 1.00 (95% confidence interval 0.78 to 1.23) with no evidence of overfitting. Birthweight was underestimated by 9.7 g on average (95% confidence interval -154.3 g to 173.8 g).

Limitations

We could not externally validate most of the published models due to variations in the definitions of outcomes. Internal-external cross-validation of our International Prediction of Pregnancy Complications-fetal growth restriction model was limited by the paucity of events in the included cohorts. The economic evaluation using the published National Institute for Health and Care Excellence 2008 model may not reflect current practice, and full economic evaluation was not possible due to paucity of data.

Future work

International Prediction of Pregnancy Complications models' performance needs to be assessed in routine practice, and their impact on decision-making and clinical outcomes needs evaluation.

Conclusion

The International Prediction of Pregnancy Complications-fetal growth restriction and International Prediction of Pregnancy Complications-birthweight models accurately predict fetal growth restriction and birthweight for various assumed gestational ages at delivery. These can be used to stratify the risk status at booking, plan monitoring and management.

Study registration

This study is registered as PROSPERO CRD42019135045.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 17/148/07) and is published in full in Health Technology Assessment; Vol. 28, No. 14. See the NIHR Funding and Awards website for further award information.

Association of common maternal infections with birth outcomes: a multinational cohort study

PURPOSE

It is unclear whether common maternal infections during pregnancy are risk factors for adverse birth outcomes. We assessed the association between self-reported infections during pregnancy with preterm birth and small-for-gestational-age (SGA) in an international cohort consortium.

METHODS

Data on 120,507 pregnant women were obtained from six population-based birth cohorts in Australia, Denmark, Israel, Norway, the UK and the USA. Self-reported common infections during pregnancy included influenza-like illness, common cold, any respiratory tract infection, vaginal thrush, vaginal infections, cystitis, urinary tract infection, and the symptoms fever and diarrhoea. Birth outcomes included preterm birth, low birth weight and SGA. Associations between maternal infections and birth outcomes were first assessed using Poisson regression in each cohort and then pooled using random-effect meta-analysis. Risk ratios (RR) and 95% confidence intervals (CI) were calculated, adjusted for potential confounders.

RESULTS

Vaginal infections (pooled RR, 1.10; 95% CI, 1.02-1.20) and urinary tract infections (pooled RR, 1.17; 95% CI, 1.09-1.26) during pregnancy were associated with higher risk of preterm birth. Similar associations with low birth weight were also observed for these two infections. Fever during pregnancy was associated with higher risk of SGA (pooled RR, 1.07; 95% CI, 1.02-1.12). No other significant associations were observed between maternal infections/symptoms and birth outcomes.

CONCLUSION

Vaginal infections and urinary infections during pregnancy were associated with a small increased risk of preterm birth and low birth weight, whereas fever was associated with SGA. These findings require confirmation in future studies with laboratory-confirmed infection diagnosis.

Sleep duration and biomarkers of fecundity in young men: a cross-sectional study from a population-based cohort

BACKGROUND

Poor male fecundity is of concern and warrants the identification of potential modifiable risk factors. Short and long sleep duration might be risk factors for poor male fecundity although evidence in this research field is inconsistent.

OBJECTIVES

To investigate the association between sleep duration and biomarkers of male fecundity in young men.

MATERIALS AND METHODS

We conducted a cross-sectional study of 1,055 young men from the Fetal Programming of Semen Quality (FEPOS) cohort, Denmark, 2017-2019. Sleep duration was obtained from an online survey answered by the participants prior to the clinical visit, where semen and blood samples were obtained, and testis volume was self-assessed using an Orchidometer. Percentage differences in semen characteristics, testes volume, and reproductive hormone levels were analysed according to sleep duration using multivariable negative binomial regression models. Sleep duration was dichotomised (recommended (6-9 h/night) versus deviant sleep) and visualised continuously as restricted cubic spline plots.

RESULTS

Deviation from recommended sleep duration was associated with higher high DNA stainability (HDS) of 5% (95% CI: -1%; 13%), higher testosterone of 3% (95% CI: 0%; 7%) and higher free androgen index (FAI) of 6% (95% CI: 0%; 13%). The spline plots overall supported these results, suggesting u-shaped associations between sleep duration and HDS, testosterone and FAI, a linear association between sleep duration and semen volume and sex hormone binding globulin (SHBG) and an inverse u-shaped association with normal morphology.

DISCUSSION

Information on sleep duration was obtained by self-report in broad categories with at least 3 h intervals. We were not able to investigate short or long sleep duration separately, since only few participants reported this.

CONCLUSION

Sleep duration was associated with some biomarkers of fecundity in young men. Maintaining a recommended sleep duration may thus be beneficial for young men with regard to reproductive health.

Stress and anxiety during pregnancy and length of gestation: a federated study using data from five Canadian and European birth cohorts

While its etiology is not fully elucidated, preterm birth represents a major public health concern as it is the leading cause of child mortality and morbidity. Stress is one of the most common perinatal conditions and may increase the risk of preterm birth. In this paper we aimed to investigate the association of maternal perceived stress and anxiety with length of gestation. We used harmonized data from five birth cohorts from Canada, France, and Norway. A total of 5297 pregnancies of singletons were included in the analysis of perceived stress and gestational duration, and 55,775 pregnancies for anxiety. Federated analyses were performed through the DataSHIELD platform using Cox regression models within intervals of gestational age. The models were fit for each cohort separately, and the cohort-specific results were combined using random effects study-level meta-analysis. Moderate and high levels of perceived stress during pregnancy were associated with a shorter length of gestation in the very/moderately preterm interval [moderate: hazard ratio (HR) 1.92 (95%CI 0.83, 4.48); high: 2.04 (95%CI 0.77, 5.37)], albeit not statistically significant. No association was found for the other intervals. Anxiety was associated with gestational duration in the very/moderately preterm interval [1.66 (95%CI 1.32, 2.08)], and in the early term interval [1.15 (95%CI 1.08, 1.23)]. Our findings suggest that perceived stress and anxiety are associated with an increased risk of earlier birth, but only in the earliest gestational ages. We also found an association in the early term period for anxiety, but the result was only driven by the largest cohort, which collected information the latest in pregnancy. This raised a potential issue of reverse causality as anxiety later in pregnancy could be due to concerns about early signs of a possible preterm birth.

Adherence to different forms of plant-based diets and pregnancy outcomes in the Danish National Birth Cohort: A prospective observational study

INTRODUCTION

The number of people adhering to plant-based diets has been increasing dramatically in recent years, fueled by both environmental and animal welfare concerns. Beneficial or possible adverse consequences of such diets, particularly the most restrictive forms during pregnancy, have been minimally explored. The aim of this prospective observational study was to examine associations between different forms of plant-based diets during pregnancy with birth outcomes and pregnancy complications.

MATERIAL AND METHODS

The Danish National Birth Cohort included 100 413 pregnancies to 91 381 women in 1996-2002. The population consisted of 66 738 pregnancies, about which sufficient dietary data were available and included in the study. Dietary and supplemental intake was assessed by Food Frequency Questionnaire in gestational week 25 and women were characterized as fish/poultry-vegetarians, lacto/ovo-vegetarians, vegans or omnivorous, based on their self-report in gestational week 30. Main outcome measures were pregnancy and birth complications, birthweight and small for gestational age.

RESULTS

A total of 98.7% (n = 65 872) of participants were defined as omnivorous, whereas 1.0% (n = 666), 0.3% (n = 183) and 0.03% (n = 18) identified themselves as fish/poultry vegetarians, lacto/ovo-vegetarians or vegans, respectively. Protein intake was lower among lacto/ovo-vegetarians (13.3%) and vegans (10.4%) than among omnivorous participants (15.4%). Intake of micronutrients was also considerably lower among vegans, but when dietary supplements were taken into consideration, no major differences were observed. Compared with omnivorous mothers, vegans had a higher prevalence of preeclampsia and their offspring had on average -240 g (95% confidence interval -450 to -30) lower birthweight.

CONCLUSIONS

The women reporting that they adhered to vegan diets during pregnancy had offspring with lower mean birthweight and higher risk of preeclampsia compared with omnivorous mothers. Low protein intake might be one plausible explanation for the observed association with birthweight.

No association between long-chain n-3 fatty acid intake during pregnancy and risk of type 1 diabetes in offspring in two large Scandinavian pregnancy cohorts

AIMS/HYPOTHESIS

The aim of this study was to investigate whether higher dietary intake of marine n-3 fatty acids during pregnancy is associated with a lower risk of type 1 diabetes in children.

METHODS

The Danish National Birth Cohort (DNBC) and the Norwegian Mother, Father and Child Cohort Study (MoBa) together include 153,843 mother-child pairs with prospectively collected data on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intake during pregnancy from validated food frequency questionnaires. Type 1 diabetes diagnosis in children (n=634) was ascertained from national diabetes registries.

RESULTS

There was no association between the sum of EPA and DHA intake during pregnancy and risk of type 1 diabetes in offspring (pooled HR per g/day of intake: 1.00, 95% CI 0.88, 1.14), with consistent results for both the MoBa and the DNBC. Robustness analyses gave very similar results.

CONCLUSIONS/INTERPRETATION

Initiation of a trial of EPA and DHA during pregnancy to prevent type 1 diabetes in offspring should not be prioritised.

Mode of birth and long-term maternal mental health: A follow-up study in the Danish National Birth Cohort

BACKGROUND

Cesarean birth has been associated with increased risks of short-term mental health problems. Little is known about whether these associations persist in the long term. This study aimed to estimate the associations between mode of birth and maternal mental health in midlife while considering mental health before and during pregnancy.

METHODS

Cohort study among mothers in the Danish National Birth Cohort. Birth mode for each woman's entire reproductive history was obtained from Danish national registries. Symptoms of depression and stress in midlife were self-reported using validated scales. Log binomial regression was used to calculate risk ratios (RR) with 95% confidence intervals (CI) for the association between birth mode and depressive symptoms. Linear regression was used to calculate mean difference in stress score by birth mode.

RESULTS

Among 42,872 women, 15.5% reported depressive symptoms at follow-up, where they were, on average, 43.9 years and 11.2 years after their last birth. Compared with women who only ever had spontaneous vaginal births, women who only had cesarean births, or had both cesarean and vaginal births with the last birth by cesarean, reported slightly more symptoms of depression (RR 1.10, 95% CI 1.01;1.20) and stress (mean difference 0.68 on a 100-point scale, 95% CI 0.10;1.26).

CONCLUSION

Whether due to the birth experience or underlying factors, depression and stress in midlife were more frequent in women with only cesarean births or whose last birth was by cesarean compared with women with vaginal births.

Characteristics of Puberty in a Population-Based Sample of Danish Adolescents

PURPOSE

To describe the duration, timing, tempo, and synchronicity of puberty, as well as the correlation between timing and tempo of puberty.

METHODS

Overall, 15,819 of 22,439 invited children participated in the Puberty Cohort within the Danish National Birth Cohort. Participants completed a web-based questionnaire every 6 months through maturation with questions on current pubertal status. Girls reported current Tanner stage of breast and pubic hair development, and timing of menarche. Boys reported current Tanner stage of genital and pubic hair development, timing of first ejaculation, and vocal changes. While accounting for this interval-censored puberty information, we estimated the duration of puberty. Then, we used a nonlinear mixed effect growth model to estimate timing, tempo, synchronicity of puberty, and correlation between timing and tempo of puberty.

RESULTS

In girls, the average duration of breast development was longer, whereas the average tempo was slower than pubic hair development. The average timing of breast development was earlier than the average timing of pubic hair development. The majority of girls had asynchronous puberty. In boys, the average duration was longer and average tempo slower for genital than pubic hair development. The average timing of genital and pubic hair development were comparable; hence, the majority had synchronous pubertal development. Adolescents who had earlier timing also tended to have a faster tempo.

DISCUSSION

Being one of the largest puberty cohorts worldwide, these unique contemporary data can help physicians, parents, and children to understand and anticipate expected progression through pubertal development.

Association of Fetal Lung Development Disorders with Adult Diseases: A Comprehensive Review

Fetal lung development is a crucial and complex process that lays the groundwork for postnatal respiratory health. However, disruptions in this delicate developmental journey can lead to fetal lung development disorders, impacting neonatal outcomes and potentially influencing health outcomes well into adulthood. Recent research has shed light on the intriguing association between fetal lung development disorders and the development of adult diseases. Understanding these links can provide valuable insights into the developmental origins of health and disease, paving the way for targeted preventive measures and clinical interventions. This review article aims to comprehensively explore the association of fetal lung development disorders with adult diseases. We delve into the stages of fetal lung development, examining key factors influencing fetal lung maturation. Subsequently, we investigate specific fetal lung development disorders, such as respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), congenital diaphragmatic hernia (CDH), and other abnormalities. Furthermore, we explore the potential mechanisms underlying these associations, considering the role of epigenetic modifications, transgenerational effects, and intrauterine environmental factors. Additionally, we examine the epidemiological evidence and clinical findings linking fetal lung development disorders to adult respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), and other respiratory ailments. This review provides valuable insights for healthcare professionals and researchers, guiding future investigations and shaping strategies for preventive interventions and long-term care.

Birth by caesarean section and semen quality in adulthood: a Danish population-based cohort study

BACKGROUND

The caesarean section (CS) rate has increased worldwide and there is an increasing public and scientific interest in the potential long-term health consequences for the offspring. CS is related to persistent aberrant microbiota colonization in the offspring, which may negatively interfere with sex hormone homeostasis and thus potentially affect the reproductive health. It remains unknown whether adult sons' semen quality is affected by CS. We hypothesize that CS is associated with lower semen quality.

METHODS

This study was based on the Fetal Programming of Semen Quality cohort (FEPOS, enrolled from 2017 to 2019) nested within the Danish National Birth Cohort (DNBC, enrolled from 1996 to 2002). A total of 5697 adult sons of mothers from the DNBC were invited to the FEPOS cohort, and 1044 young men participated in this study. Information on mode of delivery was extracted from the Danish Medical Birth Registry, and included vaginal delivery, elective CS before labor, emergency CS during labor and unspecified CS. The young men provided a semen sample for analysis of semen volume, sperm concentration, motility and morphology. Negative binomial regression models were applied to examine the association between CS and semen characteristics with estimation of relative differences in percentages with 95% confidence intervals (CIs).

RESULTS

Among included sons, 132 (13%) were born by CS. We found a slightly lower non-progressive sperm motility (reflecting higher progressive sperm motility) among sons born by CS compared to sons born by vaginal delivery [relative difference (95% CI): - 7.5% (- 14.1% to - 0.4%)]. No differences were observed for other sperm characteristics. When CS was further classified into elective CS, emergency CS and unspecified CS in a sensitivity analysis, no significant differences in non-progressive motility were observed among sons born by any of the three types of CS compared to sons born vaginally.

CONCLUSIONS

This large population-based cohort study found no significant evidence for an adverse effect on semen quality in adult sons born by CS.

Urinary Incontinence in Midlife According to Weight Changes Across and After Childbearing Years

INTRODUCTION AND HYPOTHESIS

The objective was to investigate how weight change across and after the childbearing years was associated with urinary incontinence (UI) in midlife.

METHODS

Data were obtained from 35,645 women responding to the Maternal Follow-up questionnaire in the Danish National Birth Cohort in 2013-2014. Outcome was self-reported UI and its subtypes. Exposures were changes in body mass index (BMI) across and after the childbearing years. Adjusted odds ratios were estimated using logistic regression.

RESULTS

At follow-up, the mean age was 44 years and 32% experienced UI. Compared with stable weight, weight gain across the childbearing years of > 1 to 3, > 3 to 5 or > 5 BMI units increased the odds of any UI by 15%, 27%, and 41% respectively. For mixed UI, the odds increased by 23%, 41%, and 68% in these groups. Weight gain after childbearing showed the same pattern, but with a higher increase in the odds of mixed UI (25%, 60%, and 95% in the respective groups). Women with any weight loss during this period had 9% lower odds of any UI than women with a stable weight.

CONCLUSIONS

Weight gain across and after childbearing increased the risk of UI in midlife, especially the subtype mixed UI. Weight loss after childbearing decreased the risk.

Residential exposure to mold, dampness, and indoor air pollution and risk of respiratory tract infections: a study among children ages 11 and 12 in the Danish National Birth Cohort

BACKGROUND

The burden of respiratory tract infections (RTIs) is high in childhood. Several residential exposures may affect relative rates.

OBJECTIVES

To determine risk of RTIs in children ages 11 and 12 by residential exposures.

METHODS

We included children in the Danish National Birth Cohort (DNBC) at ages 11 and 12. We estimated incidence risk ratios (IRR) and 95% confidence intervals (CI) for counts of RTIs within the last year by exposure to mold/dampness, gas stove usage, summer and winter candle-burning, fireplace usage, cats and dogs indoors, and farmhouse living. We also estimated IRR and 95% CI for RTIs for predicted scores of four extracted factors ('owned house', 'mold and dampness', 'candles', and 'density') from exploratory factor analyses (EFA).

RESULTS

We included 42 720 children with complete data. Mold/dampness was associated with all RTIs (common cold: IRRadj 1.09[1.07, 1.12]; influenza: IRRadj 1.10 [1.05, 1.15]; tonsillitis: IRRadj 1.19 [1.10, 1.28]; conjunctivitis: IRRadj 1.16 [1.02, 1.32]; and doctor-diagnosed pneumonia: IRRadj 1.05 [0.90, 1.21]), as was the EFA factor 'mold/dampness' for several outcomes. Gas stove usage was associated with conjunctivitis (IRRadj 1.25 [1.05, 1.49]) and with doctor-diagnosed pneumonia (IRRadj 1.14 [0.93, 1.39]). Candle-burning during summer, but not winter, was associated with several RTIs, for tonsillitis in a dose-dependent fashion (increasing weekly frequencies vs. none: [IRRadj 1.06 [0.98, 1.14], IRRadj 1.16 [1.04, 1.30], IRRadj 1.23 [1.06, 1.43], IRRadj 1.29 [1.00, 1.67], and IRRadj 1.41 [1.12, 1.78]).

CONCLUSION

Residential exposures, in particular to mold and dampness and to a lesser degree to indoor combustion sources, are related to the occurrence of RTIs in children.

Association of perinatal factors with neurodevelopmental referrals in a population-based cohort study in Japan

Although the causes of neurodevelopmental disorders remain unknown, several environmental risk factors have attracted considerable attention. We conducted a retrospective, longitudinal, population-based cohort study using data from infant health examinations of children born to mothers with pregnancies between April 1, 2014 and March 31, 2016 in Kobe City to identify the perinatal factors associated with neurodevelopmental referrals in 3-year-old children. There were 15,223 and 1283 children in the normal and referral groups, respectively. Neurodevelopmental referrals at the health checkup for 3-year-old children were significantly associated with the lack of social support during pregnancy (adjusted odds ratio [aOR] 1.99, 99% CI 1.14-3.45, p = 0.001), history of psychiatric consultation (aOR 1.56, 99% CI 1.10-2.22, p = 0.001), no social assistance post-delivery (aOR 1.49, 99% CI 1.03-2.16, p = 0.006), Edinburgh Post-natal Depression Scale (EPDS) score ≥ 9 (aOR 1.36, 99% CI 1.01-1.84, p = 0.008), infant gender (male) (aOR 2.51, 99% CI 2.05-3.06, p < 0.001), and cesarean delivery (aOR 1.39, 99% CI 1.11-1.75, p < 0.001). In conclusion, this exploratory study in the general Japanese population identified six perinatal factors associated with neurodevelopmental referrals in 3-year-old children: infant gender (male), cesarean section, maternal history of psychiatric consultation, EPDS score ≥ 9, lack of social support during pregnancy, and no social assistance post-delivery.

Maximising the potential of Chinese birth cohort studies: a systematic review of mother-baby cohorts in mainland China

OBJECTIVES

There is now a growing interest in early-life influences on adult diseases in China. A number of birth cohorts have been established. This systematic review provided a better understanding of the development of mother-baby cohorts in China.

STUDY DESIGN

Systematic review.

METHODS

We conducted a systematic review for research or profile papers in English/Chinese that reported data from mother-baby cohorts in mainland China, with ≥1y follow-up after birth. We identified 315 papers, corresponding to 31 cohorts from 19 provinces/megacities.

RESULTS

All cohorts started in 1999-2017 (21 after 2010) and were set up with broad objectives or specific scientific focus. The baseline sample size varied, from <500 to >300,000 mothers. A majority of cohorts were initiated during pregnancy and followed children to <10y, only six to adolescence and none into adulthood. These cohorts mostly collected samples from mothers and babies, in addition to using interviews/questionnaires to collect information about pregnancy, birth and child health. Most cohorts were recruited from a single province/city. The large western region was understudied.

CONCLUSIONS

Mother-baby cohorts have developed rapidly in China, but usually with a short follow-up duration. Extending the follow-up of children and developing cross-cohort collaboration will increase the diversity, size and coverage of the sample, allow studying early influences on life-course health and identify targets for early intervention in the Chinese population.