Birth weight of infants and mortality in their parents and grandparents: the Uppsala Birth Cohort Study

Relationship between birth weight and ambient temperature during pregnancy in a cross-sectional study of the residents of Suzhou, China

Objective

The association between birth weight and ambient temperature during pregnancy remains inconclusive, and data from Chinese populations are scarce. We conducted a cross-sectional study to investigate the association between birth weight and ambient temperature during pregnancy among the residents of Suzhou Industrial Park, Suzhou, China.

Methods

Information regarding 10,903 infants born between January 2018 and December 2018 who were born at the hospitals in Suzhou Industrial Park, Jiangsu province was obtained via public birth records.

Results

This study found that the ambient temperature during the first trimester of pregnancy was negatively correlated with birth weight, suggesting that elevated temperature may be related to lower birth weight. However, the ambient temperatures during the second and third trimesters of pregnancy were positively correlated with birth weight. Moreover, when the ambient temperature was below 15°C during the second trimester of pregnancy, the birth weight increased with temperature. However, when the temperature was higher than 15°C, the birth weight decreased with temperature. The relationship between ambient temperature in the third trimester and birth weight presented an inverted "U" curve. When the ambient temperature was lower than 20°C, the birth weight increased with ambient temperature, but when the ambient temperature was higher than 20°C, the increase of ambient temperature showed no significant relationship with the increase of birth weight.

Conclusion

The ambient temperature was correlated with birth weight. The ambient temperature during the first trimester of pregnancy was negatively correlated with birth weight. The relationship between ambient temperature in the third trimester and birth weight presented an inverted "U" curve.

Associations between parental type 2 diabetes risk and offspring birthweight and placental weight: a survival analysis using the Walker cohort

AIMS/HYPOTHESIS

Low birthweight (BW) is associated with the development of type 2 diabetes. Genome-wide analyses have identified a strong genetic component to this association, with many BW-associated loci also involved in glucose metabolism. We hypothesised that offspring BW and placental weight (PW) are correlated with parental type 2 diabetes risk, reflecting the inheritance of diabetes risk alleles that also influence fetal growth.

METHODS

The Walker cohort, a collection of birth records from Dundee, Scotland, from the 1950s and the 1960s was used to test this hypothesis by linking BW and PW measurements to parental health outcomes. Using data from SCI-Diabetes and the national death registry, we obtained health records for over 20,000 Walker parents. We performed Fine-Gray survival analyses of parental type 2 diabetes risk with competing risk of death, and Cox regression analyses of risk of death, independently in the maternal and paternal datasets, modelled by offspring BW and PW.

RESULTS

We found significant associations between increased paternal type 2 diabetes risk and reduced offspring BW (subdistribution hazard ratio [SHR] 0.92 [95% CI 0.87, 0.98]) and PW (SHR 0.87 [95% CI 0.81, 0.94]). The association of maternal type 2 diabetes risk with offspring BW or PW was not significant. Lower offspring BW was also associated with increased risk of death in both mothers (HR 0.91 [95% CI 0.89, 0.94]) and fathers (HR 0.95 [95% CI 0.92, 0.98]), and higher offspring PW was associated with increased maternal mortality risk (HR 1.08 [95% CI 1.04, 1.13]) when adjusted for BW.

CONCLUSIONS/INTERPRETATION

We identified associations between offspring BW and reduced paternal type 2 diabetes risk, most likely resulting from the independent effects of common type 2 diabetes susceptibility alleles on fetal growth, as described by the fetal insulin hypothesis. Moreover, we identified novel associations between offspring PW and reduced paternal type 2 diabetes risk, a relationship that might also be caused by the inheritance of diabetes predisposition variants. We found differing associations between offspring BW and PW and parental risk of death. These results provide novel epidemiological support for the use of offspring BW and PW as predictors for future risk of type 2 diabetes and death in mothers and fathers.

The role of cardiovascular risk factors in maternal cardiovascular disease according to offspring birth characteristics in the HUNT study

A history of preterm or small (SGA) or large (LGA) for gestational age offspring is associated with smoking and unfavorable levels of BMI, blood pressure, glucose and lipids. Whether and to what extent the excess cardiovascular risk observed in women with these pregnancy complications is explained by conventional cardiovascular risk factors (CVRFs) is not known. We examined the association between a history of SGA, LGA or preterm birth and cardiovascular disease among 23,284 parous women and quantified the contribution of individual CVRFs to the excess cardiovascular risk using an inverse odds weighting approach. The hazard ratios (HR) between SGA and LGA offspring and CVD were 1.30 (95% confidence interval (CI) 1.15, 1.48) and 0.89 (95% CI 0.76, 1.03), respectively. Smoking explained 49% and blood pressure may have explained ≈12% of the excess cardiovascular risk in women with SGA offspring. Women with preterm birth had a 24% increased risk of CVD (HR 1.24, 95% CI 1.06, 1.45), but we found no evidence for CVRFs explaining any of this excess cardiovascular risk. While smoking explains a substantial proportion of excess cardiovascular risk in women with SGA offspring and blood pressure may explain a small proportion in these women, we found no evidence that conventional CVRFs explain any of the excess cardiovascular risk in women with preterm birth.

Birthweight in offspring and cardiovascular mortality in their parents, aunts and uncles: a family-based cohort study of 1.35 million births

Background

A link between suboptimal fetal growth and higher risk of cardiovascular disease (CVD) is well documented. It has been difficult to assess the contribution of environmental versus genetic factors to the association, as these factors are closely connected in nuclear families. We investigated the association between offspring birthweight and CVD mortality in parents, aunts and uncles, and examined whether these associations are explained by CVD risk factors.

Methods

We linked Norwegian data from the Medical Birth Registry, the Cause of Death Registry and cardiovascular surveys. A total of 1 353 956 births (1967–2012) were linked to parents and one maternal and one paternal aunt/uncle. Offspring birthweight and CVD mortality association among all relationships was assessed by hazard ratios (HR) from Cox regressions. The influence of CVD risk factors on the associations was examined in a subgroup.

Results

Offspring birthweight was inversely associated with CVD mortality among parents and aunts/uncles. HR of CVD mortality for one standard deviation (SD) increase in offspring birthweight was 0.72 (0.69–0.75) in mothers and 0.89 (0.86–0.92) in fathers. In aunts/uncles, the HRs were between 0.90 (0.86–0.95) and 0.93 (0.91–0.95). Adjustment for CVD risk factors in a subgroup attenuated all the associations.

Conclusions

Birthweight was associated with increased risk of CVD in parents and in aunts/uncles. These associations were largely explained by CVD risk factors. Our findings suggest that associations between offspring birthweight and CVD in adult relatives involve both behavioural variables (especially smoking) and shared genetics relating to established CVD risk factors.

The association between birthweight and grandparental type 2 diabetes and cardiovascular disease in a multiethnic population

Intergenerational links of chronic disease have been suggested, as birthweight (BW) is associated with cardiovascular disease (CVD) and type 2 diabetes (T2D) in both parents and grandparents. However, most studies investigating these relationships have used relatively homogenous, white, majority populations. This study aimed to investigate the association between BW and CVD and T2D in a multiethnic population, that is, where the parents and grandparents often developed in a different environment from that where the child was born. Participants were women from a population-based cohort study of pregnant women (STORK Groruddalen), attending Child Health Clinics for antenatal care in three administrative city districts in Oslo, Norway, 2008-2010. Information about socioeconomic and lifestyle factors were collected among mothers and fathers. Parents reported history of CVD or T2D among grandparents. In logistic regressions, higher BW z-scores were associated with lower odds of T2D among maternal (OR 0.71 (95% CI 0.53, 0.97) and paternal (0.68 (0.49, 0.94) grandmothers after adjustments for parental and grandmothers' characteristics. BW was not associated with CVD, but the association in maternal grandfathers was borderline significant. Our results indicate intergenerational transmission of chronic diseases like T2D in a multiethnic population.

Offspring birth weight and cardiovascular mortality among parents: the role of cardiovascular risk factors

An inverse association between offspring birth weight (BW) and higher risk of parental cardiovascular disease (CVD) mortality and morbidity has been reported. Shared environmental, genetic and intrauterine factors may be responsible for explaining these associations. We studied the role of parental CVD risk factors in the association between offspring BW and CVD mortality among mothers and fathers. All births registered in Medical Birth Registry Norway (1967–2012) were linked to three health surveys, National Educational Registry and Cause of Death Registry. Number of births with information of parental CVD risk factors available for the analyses was 1,006,557 (520,670 for mothers and 485,887 for fathers). Cox proportional hazards regression models were used, following CVD deaths in parents from 1974 to 2012. An inverse association between offspring BW and CVD mortality was observed among both parents: hazard ratio 1.60 (1.44–1.75) for mothers and 1.16 (1.10–1.23) for fathers. Among mothers, adjustment for smoking, triglycerides and diabetes reduced the risk to 1.36 (1.25–1.52), 1.57 (1.43–1.73) and 1.58 (1.43–1.79), respectively. Adjustment for diastolic blood pressure (DBP) and systolic blood pressure (SBP) both reduced the risk to 1.53 (1.37–1.66). Among fathers, adjustments for smoking, DBP, SBP reduced the risk to 1.08 (1.02–1.15), 1.13 (1.06–1.19) and 1.14 (1.08–1.22), respectively. Triglycerides and diabetes both reduced the risk to 1.15 (1.09–1.12). Our results indicate that shared environmental factors might be important in the association. A stronger association in mothers suggest that intrauterine factors also are at play.

Multigenerational cohorts in patients with asthma and allergy

Recent observations that disease risk can be transmitted across generations without the need for direct exposure of the child to the index environmental insult has sparked interest in transgenerational inheritance. Epigenetics describes processes that modify gene expression without a change in the nucleotide sequence. Epigenetic processes can be induced in response to environmental exposures, can influence disease risk, and might explain these multigenerational effects. In experimental models a number of epigenetic mechanisms have been identified that could mediate vertical transmission of epigenetic inheritance. However, relevance of these findings to human disease is not yet clear. An alternative model is one in which transgenerational inheritance of disease risk requires the presence of exposure-related diseases in the mother during pregnancy (termed induced epigenetic transmission model). A number of cross-sectional studies have investigated multigenerational effects in allergy and asthma. However, given the early-life origins of asthma and allergy, birth cohort studies are ideal to investigate the effect of genetic predisposition, epigenetics, and environmental exposures, avoiding pitfalls, such as recall bias and confounding by ongoing exposures, disease, and treatment. The well-characterized 3 generations of the Isle of Wight cohort include 2 consecutive birth cohorts, providing longitudinal data that can be studied for epigenetic transfer of information, such as the effect of grand parental smoking or exposure to other toxic compounds. Further large multigenerational birth cohorts are needed to establish the clinical relevance of this phenomenon and differentiate between vertical and induced transmission models, which might influence future preventive strategies.

Predictors of adults' body mass index and the association with index child's infant birth weight, in the Lifeways Cross-Generation Cohort Study of a thousand families in the Republic of Ireland

The Lifeways study is novel in having information on three generations of the same families. It is well established that infant birth weight (IBW) predicts individuals' risk of adult chronic disease and more recently studies report cross-generation transmission of risk patterns. The aims of this analysis were to examine whether adults' birth weights were associated with measures of own health status or social position and to relate adults' birth weights to that of the index child's IBW. Finally, we assessed whether birth weight of either adults or children was associated with adult body mass index (BMI) of parents and grandparents. We included 1075 children whose IBW was recorded at recruitment from hospital records and 2546 adult cohort members followed from 2001 until 2014. At baseline, a sub-group of 920 adults had reported own birth weight (RBW). Results showed male adults' RBW were significantly higher than females' (P=0.001). Mothers' RBW was significantly correlated with IBW (r=0.178, P<0.001). In mixed effects linear models with BMI as the outcome variable, of all adults, and in sub-groups of adults with RBW and of mothers only, the IBW was associated with adult BMI adjusting for other predictors. Adults' BMI was positively associated with age (P=0.013), index child's IBW (P=0.001), gender (P<0.001) but not own RBW, adjusting for family identification number. When mothers were removed from the adult models however, IBW ceased to be associated with BMI, a final model showed RBW being associated with adult BMI (P=0.04). There are cross-generational associations in the Lifeways cohort, the maternal association being stronger.

Grandparental morbidity and mortality patterns are associated with infant birth weight in the Lifeways cross-generation cohort study 2001-2010

The association of infants' birth weight with maternal cardiovascular morbidity (CVD) and mortality substantiates the foetal origins hypothesis. Few studies to date have investigated grandparent-infant risk association. We prospectively examined this relationship in the Lifeways three-generation familial cohort, contrasting lineage and gender differences to understand mechanisms of intergenerational risk transmission. In 2001, a cohort of 1082 families was established at antenatal stage. A total of 539 families (n = 539 infants) had both a participating grandparent (n = 1054) and information on infants' gestational age. At baseline, grandparents provided their diagnosed CVD status and 79% also underwent a cardiovascular risk factors assessment. In 2005, general practitioners provided an update for 61% grandparents. In 2010, a search of civil register confirmed 77 grandparental deaths in 539 families. Grandchildren's birth weight and grandparental cardiovascular risk factors associations were examined with linear regressions. Grandparental CVD associations were analysed using ANCOVA. Cox proportional hazard ratios (HR) were calculated for all-cause mortality associations. Models were adjusted for infants', mothers' and grandparents' demographic, anthropometric and socio-behavioural characteristics, as appropriate. The paternal grandfathers' (PGF) systolic blood pressure (mmHg) [β (95% CI) = 6.6 (0.8 - 12.5); P = 0.03] and paternal grandmothers' serum triglycerides (mmol/l) [β (95% CI) = 78.8 (7.0 - 150.7); P = 0.03] were linearly predictive of infants' birth weight, which was not observed for maternal grandparents. Mean birth weight for infants of maternal grandmothers with diabetes {-272.7 [(-499.7) - (-45.6)] g; P = 0.02} or stroke {-292.1 [(-544.5) - (-39.6)] g; P = 0.02} was lower than those without diabetes or stroke, a pattern not observed for paternal grandparents. Whereas PGFs' mortality was significantly associated with infants' high birth weight (≥4000 g) [HR (95% CI) = 4.9 (1.2 - 19.9); P = 0.03], maternal grandparents' mortality showed a converse pattern with infants' low birth weight (<2500 g) [HR (95% CI) = 1.7 (0.4 - 8.2); P = 0.7], although not statistically significant. These findings suggest that intergenerational transmission of risk differs in maternal and paternal lines.

Other adverse pregnancy outcomes and future chronic disease

Cardiovascular disease is the leading cause of morbidity and mortality in females worldwide. Pregnancy is associated with significant physiologic changes that may function as a natural stress test to detect women at future risk. It is established that women who have had a pregnancy complicated by gestational diabetes or a hypertensive disorder of pregnancy are at increased risk of cardiovascular disease later in life, and there is growing evidence that women who deliver infants preterm or growth-restricted infants have an elevated risk as well. Consideration should be given to including these outcomes as indicators of cardiovascular risk. Pregnancy represents a teachable moment when it would be ideal to identify women at risk. Improved integration of women's primary health care and an enhanced knowledge base on the part of clinicians will be necessary to fully incorporate these findings into the clinical care of women.

Body mass index is associated with the maternal lines but height is heritable across family lines in the Lifeways Cross-Generation Cohort Study

OBJECTIVES

Overweight and obesity is a problem in children in particular and determining pathways of transmission is important in prevention. We aimed to examine associations for body mass index (BMI) across three generations of the same families.

PARTICIPANTS

Members of 556 families in the Lifeways Cross-Generation Cohort Study 2001-2014.

SETTING

Community-based study with linkage to health records in the Republic of Ireland.

METHODS

Employing a novel mixed-method approach which adjusts for age and familial group, BMI correlations were estimated at three ages of the index child, that is, at birth and at ages 5 and 9. Height was also examined for comparative purposes.

RESULTS

Correlation of offspring's BMI with that of the mother increased with age (correlation coefficient 0.15 increasing to 0.28, p value <0.001 in all cases) while no consistent pattern was seen with offspring and fathers. There was an association also with each parent and their own mother. Offspring's BMI was correlated to a lesser extent with that of the maternal grandmother while for girls only there was an association with that of the paternal grandmother at ages 0 and 5 (correlation coefficients 0.25, 0.28, p values 0.02, 0.01, respectively). In contrast, height of the child was strongly associated with those of all family members at age 5, but at birth and at age 9 only there was an association with those of the parents and the paternal grandfather. Correlation of offspring's height with those of the mother and father increased with age.

CONCLUSIONS

The results suggest that BMI is predominantly associated with the maternal line, possibly either with intrauterine development, or inherited through the X chromosome, or both, while height is a more complex trait with genetic influences of the parents and that of the paternal grandfather predominating.

Longitudinal follow-up of the relationship between dietary intake and growth and development in the Lifeways cross-generation cohort study 2001-2013

In this paper we will review evidence on the early life and familial influences on childhood growth and development, with particular reference to the Lifeways cross-generation cohort study in the Republic of Ireland. The Lifeways cross-generation cohort study was established in 2001-2013 through two maternity hospitals in the Republic of Ireland and was one of many new cohort studies established worldwide in the millennium period. Mothers were recruited at first booking visit, completing a self-administered questionnaire, which included a 147 item semi-quantitative FFQ. Longitudinal follow-up is ongoing in 2013, with linkage data to hospital and general practice records and examination of children when aged 5 and 9 years. The study is one of very few containing data on grandparents of both lineages with at least one grandparent recruited at baseline. There have been consistent associations between parental and grandparental health status characteristics and children's outcomes, including infant birth-weight, BMI when child was aged 5 years and childhood wheeze or asthma when child was aged 3 and aged 5 years. In conclusion, empirical evidence to date shows consistent familial and cross-generational patterns, particularly in the maternal line.

Does the developmental plasticity hypothesis have application to Irish Travellers? Findings from the all Ireland Traveller Health Study birth cohort 2008–2011

There is little record of birth weight of Irish Travellers, a minority group in Ireland. Travellers are known to have higher rate of adult chronic disease and to be exposed to life-long disadvantage. The aim of this study was to establish whether the birth weight and infant mortality rate patterns in Ireland's Travellers were consistent with the developmental plasticity hypothesis. A 1-year follow-up birth cohort study was conducted with linkage data from maternity hospital records of Traveller infants born on the island of Ireland over a 12-month period to self-identifying Traveller and general Irish population mothers from the Lifeways Cross-Generation Cohort Study. The main outcome measure was the rate of birth weight <3000 g in a cohort of Traveller children. There were 987 confirmed Traveller births, 500 of whose mothers consented to linkage to their records. A social gradient was observed in the distribution of birth weight in the general population and Traveller infants constituted the highest proportion of all social classes in the birth weight range of 3 kg or less (16.3%). There was a high rate of persistent smoking among Traveller mothers (53%). After adjustment for smoking and alcohol consumption in pregnancy, the birth weight differential persisted (OR 3.5, 95% CI 1.4–8.1). Infant mortality rate at 12.0/1000 births (95% CI 5.5–19.7) was almost four times that of the general population. This analysis confirms Travellers had a greater than expected incidence of low birth weight and high infant mortality with high rates of premature adult chronic diseases from all causes already demonstrated previously.

Birth weight predicts risk of cardiovascular disease within dizygotic but not monozygotic twin pairs: a large population-based co-twin-control study

BACKGROUND

The widely reported inverse association between birth weight and risk of cardiovascular disease (CVD) has sparked theories about early life determinants of adult disease. Within-twin-pair analysis provides a unique opportunity to investigate whether factors shared within twin pairs influence the association.

METHODS AND RESULTS

In a population-based cohort of like-sexed twins with known zygosity born in Sweden from 1926 to 1958, disease-discordant twin pairs were identified through linkage to the National Inpatient and Cause of Death registers between 1973 and 2006. Co-twin-control analyses were performed on twins discordant for cardiovascular disease (n=3884), coronary heart disease (n=2668), and stroke (n=1372). Overall, inverse associations between birth weight and risk of cardiovascular diseases were seen within dizygotic but not monozygotic twin pairs. In dizygotic twins, the odds ratios for a 1-kg within-pair increase in birth weight were 0.74 (95% confidence interval, 0.56 to 0.98) for coronary heart disease and 0.57 (95% confidence interval, 0.37 to 0.88) for stroke. Conversely, no statistically significant associations were found within monozygotic twins (for coronary heart disease: odds ratio, 1.10; 95% confidence interval, 0.73 to 1.68; for stroke: odds ratio, 0.92; 95% confidence interval, 0.48 to 1.80).

CONCLUSIONS

We found an association between birth weight and risk of cardiovascular disease within disease-discordant dizygotic but not monozygotic twin pairs. This indicates that the association between birth weight and cardiovascular disease could be a result of common causes, and that factors that vary within dizygotic but not monozygotic twin pairs may help identify them.