Maternal Overweight and Obesity and Genital Anomalies in Male Offspring: A Population-Based Swedish Cohort Study

Maternal pre-pregnancy BMI and reproductive health in adult sons: a study in the Danish National Birth Cohort

STUDY QUESTION

Is maternal pre-pregnancy BMI associated with semen quality, testes volume, and reproductive hormone levels in sons?

SUMMARY ANSWER

Maternal pre-pregnancy BMI was associated with an altered reproductive hormone profile in young adult sons, characterized by higher levels of oestradiol, LH, and free androgen index (FAI) and lower levels of sex hormone-binding globulin (SHBG) in sons born of mothers with pre-pregnancy overweight and obesity.

WHAT IS KNOWN ALREADY

Evidence suggests that maternal pre-pregnancy BMI may influence reproductive health later in life. Only one pilot study has investigated the association between maternal pre-pregnancy BMI and reproductive health outcomes in sons, suggesting that a high BMI was associated with impaired reproductive function in the adult sons.

STUDY DESIGN, SIZE, DURATION

A population-based follow-up study of 1058 young men from the Fetal Programming of Semen Quality (FEPOS) cohort nested within the Danish National Birth Cohort (DNBC), 1998-2019, was carried out.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 1058 adult sons (median age 19 years, 2 months), born 1998-2000 by mothers included in the DNBC, participated in FEPOS. At a clinical examination, they provided a semen and blood sample, measured their testes volume, and had height and weight measured. Maternal pre-pregnancy BMI was obtained by self-report in early pregnancy. Semen characteristics, testes volume, and reproductive hormone levels were analysed according to maternal pre-pregnancy BMI categories and as restricted cubic splines using negative binomial and ordinary least square regression models. Mediation analyses examined potential mediation by the sons' birthweight, pubertal timing, fat mass, and BMI. Additional analyses investigated the role of paternal BMI in the potential associations between maternal BMI and reproductive health outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

We found no consistent associations between maternal pre-pregnancy BMI and semen characteristics or testes volume. Sons of mothers with higher pre-pregnancy BMI had higher oestradiol and lower SHBG levels, both in a dose-dependent manner. Sons of mothers with pre-pregnancy obesity (≥30 kg/m2) had higher LH levels and a higher FAI than sons born by mothers with normal pre-pregnancy BMI (18.5-24.9 kg/m2). The mediation analyses suggested that the effect of maternal pre-pregnancy BMI on higher levels of oestrogen, LH, and FAI was partly mediated by the sons' birthweight, in addition to adult fat mass and BMI measured at the clinical examination, whereas most of the effect on lower levels of SHBG was primarily mediated by the sons' own fat mass and BMI. Paternal BMI was not a strong confounder of the associations in this study.

LIMITATIONS, REASONS FOR CAUTION

This study was based in a population-based cohort with a low prevalence of overweight and obesity in both mothers and adult sons. Some men (10%) had blood for reproductive hormone assessment drawn in the evening. While several potential confounding factors were accounted for, this study's inherent risk of residual and unmeasured confounding precludes provision of causal estimates. Therefore, caution should be given when interpreting the causal effect of maternal BMI on sons' reproductive health.

WIDER IMPLICATIONS OF THE FINDINGS

Given the widespread occurrence of overweight and obesity among pregnant women, it is imperative to thoroughly examine the potential consequences for reproductive hormone levels in adult sons. The potential effects of maternal pre-pregnancy obesity on sons' reproductive hormone profile may potentially be partly avoided by the prevention of overweight and obesity in the sons.

STUDY FUNDING/COMPETING INTEREST(S)

The project was funded by the Lundbeck Foundation (R170-2014-855), the Capital Region of Denmark, Medical doctor Sofus Carl Emil Friis and spouse Olga Doris Friis's Grant, Axel Muusfeldt's Foundation (2016-491), AP Møller Foundation (16-37), the Health Foundation, Dagmar Marshall's Fond, Aarhus University, Independent Research Fund Denmark (9039-00128B), and the European Union (ERC, BIOSFER, 101071773). Views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible. The authors declare that they have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Low placental weight may be involved in the etiology of congenital cryptorchidism in neonatal boys

INTRODUCTION

Several factors have been reported to be associated with the etiology of cryptorchidism; however, clear evidence regarding the risk factors for cryptorchidism is elusive. In the present study, we evaluated the clinical characteristics of cryptorchidism using the common neonatal intensive-care unit (NICU) database of the National Hospital Organization and explored one of possible factors associated with the development of cryptorchidism.

METHODS

A total of 7882 male neonates were included in this study. We separated them into two groups: those without cryptorchidism (n = 7852) and those with cryptorchidism (n = 30) at the time of discharge from the NICU. Cryptorchidism was defined as a condition in which the testis was located out of the scrotum on the route of descent at the time of NICU discharge. The associations between cryptorchidism and the maternal, placental, and neonatal information were analyzed. Analyses were performed statistically to compare nominal variables between the groups using Fisher's direct establishment calculation method and logistic regression analyses.

RESULTS

Univariate analyses showed the placental weight <10% tile (odds ratio 3.31, 95% confidence interval [CI] 1.18-8.64), birth height <-2 standard deviations (SD) (odds ratio 3.65, 95% CI 0.92-10.6), birth weight <-2SD (odds ratio 4.06, 95% CI 1.55-9.51), and small for gestational age (odds ratio 3.82, 95% CI 1.46-8.97) were significantly associated with the development of cryptorchidism. Multivariate analyses showed that placental weight <10th percentile (odds ratio 2.86, 95% CI 1.11-7.44) was significantly associated with the development of cryptorchidism.

DISCUSSION

Although, this study population was limited to infants admitted to the ICU, the data indicated a possible association between low placental weight and the development of cryptorchidism in neonatal boys.

Maternal Cigarette Smoking During Pregnancy and Genital Anomalies in Boys: A Register-Based Cohort and Sibling-Matched Design Study

Purpose

Cryptorchidism and hypospadias share several prenatal risk factors. However, in published studies, boys exposed to cigarette smoking during pregnancy have a higher risk of cryptorchidism and a lower risk of hypospadias. Using Danish register-based data, we revisited these findings with a cohort and sibling-matched design to investigate the potential effect of shared time-stable factors.

Patients and Methods

For the cohort study, we included 823,670 live-born, singleton boys born from 1991 to 2016. Crude and adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using Cox regression models for each genital anomaly according to maternal cigarette smoking during pregnancy. For the sibling-matched design, we included 399,258 brothers and used a stratified Cox regression model creating family-adjusted results.

Results

In the cohort study, we found a higher risk of cryptorchidism (aHR = 1.18, 95% CI: 1.12, 1.24) and a lower risk of hypospadias (aHR = 0.84, 95% CI: 0.76, 0.93) when comparing boys exposed to cigarette smoking with non-exposed, and for increasing numbers of cigarettes smoked. In comparison, the sibling-matched analyses suggested a slightly weaker association for cryptorchidism and an association of similar magnitude for hypospadias, both in the same direction as in the cohort study.

Conclusion

Shared, familial confounding does not seem to explain earlier findings of higher risk of cryptorchidism and lower risk of hypospadias.

Lifestyle in Pregnancy and Hypospadias in Sons: A Study of 85,923 Mother-Son Pairs from Two Danish Pregnancy Cohorts

Purpose

Hypospadias is one of the most frequent male congenital malformations. It remains controversial whether maternal lifestyle during pregnancy may affects the risk of having a son with hypospadias, especially for smoking with many suggesting lower risk. We assessed the individual and joint associations between maternal cigarette smoking, pre-pregnancy body mass index (BMI), alcohol consumption, binge drinking, and caffeine consumption and occurrence of hypospadias in sons.

Patients and Methods

This cohort study utilized the Danish National Birth Cohort and the Aarhus Birth Cohort, holding detailed information on lifestyle factors in early pregnancy between 1989 and 2012. The Danish health registers were used to identify boys with hypospadias, according to International Classification of Diseases. Potential confounders and covariates were identified by literature search and use of directed acyclic graphs. Missing data were handled by multiple imputation and Cox proportional hazards models were applied to analyse data.

Results

In total, 85,923 live-born singleton boys were included in the study of whom 502 (0.6%) were diagnosed with hypospadias. Maternal smoking in early pregnancy was associated with lower occurrence of hypospadias. An increase of one cigarette smoked per day was associated with lower risk of having a son with hypospadias (adjusted hazard ratio (HR) 0.97 (95% confidence interval (CI) 0.94, 1.00)). However, sub-analyses suggested that the results may be prone to unadjusted confounding. We found no association between pre-pregnancy BMI, alcohol consumption, binge drinking, or caffeine consumption and hypospadias.

Conclusion

Maternal smoking during pregnancy was associated with lower occurrence of hypospadias but we cannot exclude uncontrolled confounding. The other investigated maternal lifestyle factors were not associated with hypospadias in sons.

Maternal pre-pregnancy overweight and infertility in sons and daughters: A cohort study

INTRODUCTION

Overweight and obesity in pregnancy is increasing worldwide and may harm the developing fetus, including its future reproductive health. We therefore studied the association between in utero exposure to maternal overweight and obesity and infertility in adulthood. No studies have previously assessed this association.

MATERIAL AND METHODS

We performed a cohort study with 9232 adult sons and daughters whose mothers were enrolled in the Danish Healthy Habits for Two cohort during pregnancy in 1984-87. Participants were sons and daughters followed in the Danish In-Vitro-Fertilization-Register and Danish National Patient Register until February 2018 for diagnoses of infertility.

RESULTS

In total, 1203 (13%) sons and daughters were born to mothers with a body mass index (BMI) >25 kg/m² ; 871 (9.4%) of the participants were identified as being infertile during follow-up. Sons of overweight mothers had slightly increased odds of infertility compared with sons of mothers with normal body weight (BMI 18.5-24.9 kg/m² , adjusted odds ratio 1.4, 95% confidence interval [CI] 1.0-1.9). Cubic spline analyses with continuous BMI levels showed increasing odds with higher levels of BMI; however, for BMI >29 kg/m² the confidence intervals were too wide to draw conclusions. No association between maternal overweight and infertility was found among daughters (adjusted odds ratio 0.9, 95% CI 0.7-1.2)).

CONCLUSIONS

Sons born to overweight mothers had higher odds of infertility compared with sons of normal weight mothers. No association between maternal overweight and infertility was observed in daughters. Prevention of overweight during pregnancy may be an important tool to preserve fecundity in future generations.

Measured weight in early pregnancy is a valid method for estimating pre-pregnancy weight

Estimation of pre-pregnancy weight is difficult because measurements taken before pregnancy are rarely available. No studies have compared various 'proxy' measures using recalled weight or based on early pregnancy weight with actual measurements of pre-pregnancy weight. The Southampton Women's Survey recruited women during 1998-2002 who were not pregnant. Data on 198 women with an estimated date of conception within 3 months of recruitment were analysed. Three proxy measures were considered: (1) recalled pre-pregnancy weight obtained during early pregnancy, (2) measured weight in early pregnancy and (3) estimated pre-pregnancy weight using a published model. Mean (standard deviation) recalled weight was 1.65 (3.03) kg lighter than measured pre-pregnancy weight, while early pregnancy weight and weights from the published model were 0.88 (2.34) and 0.88 (2.33) kg heavier, respectively. The Bland-Altman limits of agreement for recalled weight were -7.59 to 4.29 kg, wider than those for the early pregnancy weight: -3.71 to 5.47 kg and the published model: -3.68 to 5.45 kg. For estimating pre-pregnancy weight, we recommend subtraction of 0.88 kg from early pregnancy weight or the published model, or addition of 1.65 kg to recalled weight. Estimates of pre-pregnancy body mass index and gestational weight gain categories were very similar when using early pregnancy and published model weights, but they differed from those using recalled weight. Our findings indicate that calculations of first trimester weight gain using recalled weight must be treated cautiously, and a measured weight in early pregnancy provides a more precise assessment of pre-pregnancy weight than recalled weight.

How boys and testicles wander to surgery: a nationwide cohort study of surgical delay in Sweden

BACKGROUND

Early orchidopexy is recommended for cryptorchidism and the surgery is increasingly centralised. The objectives were to determine the incidence, risk factors and if distance to treating hospital impacted on timely treatment of cryptorchidism.

METHODS

In this observational study, all boys born in Sweden from 2001 to 2014 were followed in national registers to determine the incidence of cryptorchidism by levels of birth-related risk factors and social determinants. Travel time to hospital was used as the primary exposure in multivariable survival analysis, with age at surgery as main outcome.

RESULTS

Of 748 678 boys at risk for cryptorchidism, 7351 were treated and evaluated for timing of surgery (cumulative childhood incidence 1.4%, 95% CI 1.3% to 1.5%). The incidence was clearly associated with prematurity and overdue pregnancy (HR for <32 weeks 2.77 (95% CI 2.39 to 3.21); 32-36 weeks HR 1.36 (95% CI 1.24 to 1.49); >41 weeks HR 1.19 (95% CI 1.10 to 1.29)), low birth weight (<1000 g HR 3.94 (95% CI 3.15 to 4.92); 1000-1499 g HR 3.70 (95% CI 3.07 to 4.46); 1500-2500 g HR 1.69 (95% CI 1.52 to 1.88)) and intrauterine growth restriction (small for gestational age HR 2.38 (95% CI 2.14 to 2.65); large for gestational age HR 1.26 (95% CI 1.13 to 1.42)), but not with smoking or maternal age. Each 30 min increase in travel time was associated with a reduced probability of timely treatment (HR for being treated by age 3 adjusted for risk factors and socioeconomic determinants: 0.91 (95% CI 0.88 to 0.95)). Lower income and financial support were also associated with treatment delays (adjusted HR for lowest income quintile 0.82 (95% CI 0.72 to 0.93) and for families with financial support 0.85 (95% CI 0.73 to 0.97)).

CONCLUSIONS

Travel distance to treating hospital was associated with delayed treatment. 'Not all those who wander are lost', but these findings suggest a trade-off between centralisation benefits and barriers of geography also in elective paediatric surgery.

Altered mechanisms of genital development identified through integration of DNA methylation and genomic measures in hypospadias

Hypospadias is a common birth defect where the urethral opening forms on the ventral side of the penis. We performed integrative methylomic, genomic, and transcriptomic analyses to characterize sites of DNA methylation that influence genital development. In case–control and case-only epigenome-wide association studies (EWAS) of preputial tissue we identified 25 CpGs associated with hypospadias characteristics and used one-sample two stage least squares Mendelian randomization (2SLS MR) to show a causal relationship for 21 of the CpGs. The largest difference was 15.7% lower beta-value at cg14436889 among hypospadias cases than controls (EWAS P = 5.4e−7) and is likely causal (2SLS MR P = 9.8e−15). Integrative annotation using two-sample Mendelian randomization of these methylation regions highlight potentially causal roles of genes involved in germ layer differentiation (WDHD1, DNM1L, TULP3), beta-catenin signaling (PKP2, UBE2R2, TNKS), androgens (CYP4A11, CYP4A22, CYP4B1, CYP4X1, CYP4Z2P, EPHX1, CD33/SIGLEC3, SIGLEC5, SIGLEC7, KLK5, KLK7, KLK10, KLK13, KLK14), and reproductive traits (ACAA1, PLCD1, EFCAB4B, GMCL1, MKRN2, DNM1L, TEAD4, TSPAN9, KLK family). This study identified CpGs that remained differentially methylated after urogenital development and used the most relevant tissue sample available to study hypospadias. We identified multiple methylation sites and candidate genes that can be further evaluated for their roles in regulating urogenital development.

Effects of Overweight and Obesity in Pregnancy on Health of the Offspring

Overweight and obesity in pregnancy confer a wide range of risks on mother, fetus, and offspring throughout their lives. In addition to compounding many common pregnancy complications, including both iatrogenic preterm delivery and cesarean delivery, obesity is associated with multiple fetal anomalies, metabolic sequelae including diabetes and obesity, allergy and asthma, attention-deficit disorder, and likely many other challenges for the offspring. As targeted interventions are being developed, encouraging solid nutrition and exercise in women of childbearing age may stave off risks and mitigate obesity in the next generation.

Nationwide Increase in Cryptorchidism After the Fukushima Nuclear Accident

OBJECTIVE

To estimate the change of discharge rate after cryptorchidism surgery between pre- and postdisaster in Japan. Cryptorchidism cannot be diagnosed before birth and is not a factor that would influence a woman's decision to seek an abortion. Therefore, this disease is considered suitable for assessing how the Great East Japan Earthquake and the subsequent Fukushima Daiichi nuclear accident (2011) influenced congenital diseases.

MATERIALS AND METHODS

We obtained cryptorchidism discharge data collected over 6 years from hospitals that were included in an impact assessment survey of the Diagnosis Procedure Combination survey database in Japan and used these data to estimate the discharge rate after cryptorchidism surgery before and after the disaster. The 94 hospitals in Japan that participated in Diagnosis Procedure Combination system and had 10 or more discharges after cryptorchidism surgery within successive 6 years covering pre- and postdisaster period (FY2010-FY2015) were involved. The change in discharge rate between pre- and postdisaster was analyzed using a Bayesian generalized linear mixed model.

RESULTS

Nationwide, a 13.4% (95% credible interval 4.7%-23.0%) increase in discharge rates was estimated. The results of all sensitivity analyses were similar to the reported main results.

CONCLUSION

The discharge rate of cryptorchidism was increased nationwide. The rates of low-weight babies or preterm births, risk factors of cryptorchidism, were almost constant during the study period, and age distribution of the surgery was also not changed, which suggested that the other factors that associated with the disaster increased the incidence of cryptorchidism.

Lifestyle in pregnancy and cryptorchidism in sons: a study within two large Danish birth cohorts

Purpose

Cryptorchidism is the most frequent congenital malformation in boys and is associated with low sperm count, infertility and testicular cancer. Unhealthy maternal lifestyle during pregnancy such as smoking, high prepregnancy body mass index (BMI) as well as alcohol and caffeine intake may constitute possible risk factors for cryptorchidism, but results from the few previous studies are conflicting. We aimed to explore the association between maternal lifestyle factors and occurrence of cryptorchidism in sons.

Patients and methods

The Danish National Birth Cohort and the Aarhus Birth Cohort provided information on maternal lifestyle from early pregnancy. Data were linked to several Danish health registers, multiple imputation was used to handle missing data and Cox proportional hazards models were used to adjust for potential confounders.

Results

In total, 85,923 boys were included, and of them, 2.2% were diagnosed with cryptorchidism. We observed the strongest associations between maternal tobacco smoking and prepregnancy BMI and cryptorchidism. Sons of women who smoked 10–14 cigarettes/day had the highest hazard ratio (HR) for cryptorchidism (1.37; 95% CI: 1.06–1.76), and for maternal BMI ≥30 kg/m², the HR was 1.32 (95% CI: 1.06–1.65). Binge drinking was associated with an HR <1, if the women had one or two episodes in pregnancy (HR: 0.81; 95% CI: 0.67–0.98). Average maternal alcohol intake and caffeine intake during pregnancy were not significantly associated with a higher occurrence of cryptorchidism detected at birth or later in life.

Conclusion

Maternal tobacco smoking, overweight and obesity in pregnancy were associated with higher occurrence of cryptorchidism in boys in this study.