Genetic and environmental factors affecting birth size variation: a pooled individual-based analysis of secular trends and global geographical differences using 26 twin cohorts

Sex-Specific Effects of Birth Weight on Longitudinal Behavioral Outcomes: A Mendelian Randomization Approach Using Polygenic Scores

Background

It is unclear whether sex differences in behavior arising from birth weight (BW) are genuine because of the cross-sectional nature and potential confounding in previous studies. We aimed to test whether sex differences associated with BW phenotype were reproducible using a Mendelian randomization approach, i.e., association between polygenic score (PGS) for BW and behavior outcomes across childhood and adolescence.

Methods

Using data from the Raine Study, we had 1484 genotyped participants with a total of 6446 Child Behavior Checklist assessments from ages 5 to 17 years. We used BW-PGSs in linear mixed-effect models to predict parentally assessed attention, aggression, and social problems scales; we also derived estimates and significance for a sex-by-genotype interaction. We used a Bonferroni-corrected significance threshold and tested robustness of the results with teacher assessments of behavior and a second PGS.

Results

We found a sex-by-genotype interaction with lower BW-PGSs associated with increased aggression in males compared with females. These findings were consistent across various analyses, including teacher assessments. Surprisingly, a lower BW-PGS showed protective effects in females, while a lower BW phenotype had detrimental effects in males with evidence of a genotype-phenotype mismatch increasing aggression problems in males only.

Conclusions

This study underscores the genuine nature of behavioral sex differences arising from low BW and highlights the sex-dependent and diverging effects of environmental and genetic BW determinants.

Assessing the diagnostic accuracy of postnatal clinical scoring methods and foot length measurement for estimating gestational age and birthweight of newborns in low- and middle-income countries: a systematic review and meta-analysis

BACKGROUND

This study aimed to update systematic reviews and meta-analyses on the diagnostic accuracy of postnatal clinical scoring (PCS) methods and foot length (FL) measurement for assessing gestational age (GA) and birth weight in low-income and middle-income countries (LMICs). In addition, the quality of reference standards, including antenatal ultrasound (A-US), last menstrual period (LMP), PCS and newborn weighing scales, was also evaluated.

METHODS

Studies from LMICs published between January 2000 and February 2024 were searched, using databases such as PubMed, Web of Science, Cochrane Library, CINAHL and Scopus. Studies that compared PCS and/or FL with LMP and/or A-US to estimate GA or used calibrated newborn weighing scales for birthweight estimation were included. The risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-II tool and evaluated the quality of the reference standards. When sufficient data were available, pooled estimates were calculated using random-effects models.

RESULTS

A total of 50 studies were included. A-US was a reasonable tool for GA assessment if conducted by physicians using fetal biometry and the Hadlock method for GA estimation. LMP was reasonable when women had regular cycles, knew their LMP, were not using contraceptives and LMP data were collected by healthcare providers. When A-US was used as the reference standard, PCS methods estimated GA with a precision of ±2.8 to ±3.2 weeks. FL measurement <7.5 cm showed a pooled sensitivity of 76.2% and specificity of 36.6% for identifying preterm birth. FL measurement ≤7.6 cm had a pooled sensitivity of 78.6% and specificity of 65.7% for identifying low birth weight (LBW). High heterogeneity across studies was observed.

CONCLUSION

This systematic review and meta-analysis highlights significant variability and methodological inconsistencies in using PCS methods and FL measurement for estimating GA and LBW in LMICs. The observed high heterogeneity across studies suggests a cautious interpretation of the results.

PROSPERO REGISTRATION NUMBER

CRD42020209455.

Birth size, school performance and family social position: a study of 650,000 children

BACKGROUND

Low birth weight (BW) is associated with lower cognitive functioning, but less is known of these associations across the full range of the BW distribution and its components. We analyzed how BW, birth length (BL) and birth ponderal index (BPI, kg/m3) are associated with school performance and how childhood family social position modifies these associations.

METHODS

Medical birth records of all Finnish children born in 1987-1997 were linked to school performance records at 16 years of age (N = 642,425). We used population averaged and within-siblings fixed-effects linear regression models.

RESULTS

BL showed a linear and BW a curvilinear association with school performance whereas for BPI the association was weak. The strongest association was found for BL explaining 0.08% of the variation in school performance in boys and 0.14% in girls. Demographic, gestational and social factors partly explained these associations. Similar but weaker associations were found within sibships. The association of BL with school performance was stronger at lower levels of family social position.

CONCLUSION

BL shows a linear association with school performance and can explain more school performance variation than BW. At the population level, BL can offer useful information on intrauterine environmental factors relevant for cognitive performance.

IMPACT

Birth length is linearly associated with school performance in late adolescence and explains a larger proportion of school performance variation than birth weight. The association between birth length and school performance is stronger in families with lower socio-economic position. At the population level, birth length can offer information on the intrauterine environment relevant for later cognitive performance.

Maternal exposure to extreme high-temperature, particulate air pollution and macrosomia in 14 countries of Africa

BACKGROUND

Macrosomia has increased rapidly worldwide in the past few decades, with a huge impact on health. However, the effect of PM_2.5 and extreme high-temperature (EHT) on macrosomia has been ignored.

OBJECTIVE

This study aimed to explore the association between maternal exposure to EHT, PM_2.5 and macrosomia based on the Seventh Demographic and Health Survey (DHS) in 14 countries of Africa.

METHODS

The study included detailed demographic information on 106 382 births and maternal. Satellite inversion models estimated monthly mean PM_2.5 and mean surface temperature of 2 m (SMT_2m ). Macrosomia was defined as the birth weight ≥ 4000 g. We used a Cox proportional risk regression model to estimate the association between PM_2.5 , EHT and macrosomia. We further explored the susceptibility of exposure to EHT and PM_2.5 at different pregnancy periods to macrosomia, and plotted the expose-response curve between PM_2.5 and macrosomia risk using a restricted cubic spline function. In addition, the Interplot model was used to investigate the interaction between EHT and PM_2.5 on macrosomia. Finally, some potential confounding factors were analysed by stratification.

RESULTS

There was the positive association between EHT, PM_2.5 and macrosomia, and the risk of macrosomia with the increase in concentrations of PM_2.5 without clear threshold. Meanwhile, EHT and PM_2.5 had a higher effect on macrosomia in middle/later and early/middle stages of pregnancy, respectively. There was a significant interaction between EHT and PM_2.5 on macrosomia.

CONCLUSIONS

Maternal exposure to EHT, PM_2.5 during pregnancy was associated with an increased risk of macrosomia in Africa.

Emission of Industrial Air Pollution and Mortality Due to Respiratory Diseases: A Birth Cohort Study in Poland

BACKGROUND

Air pollution is a major risk factor for public health worldwide, but evidence linking this environmental problem with the mortality of children in Central Europe is limited.

OBJECTIVE

To investigate the relationship between air pollution due to the emission of industry-related particulate matter and mortality due to respiratory diseases under one year of age.

METHODS

A retrospective birth cohort analysis of the dataset including 2,277,585 children from all Polish counties was conducted, and the dataset was matched with 248 deaths from respiratory diseases under one year of age. Time to death during the first 365 days of life was used as a dependent variable. Harmful emission was described as total particle pollution (TPP) from industries. The survival analysis was performed using the Cox proportional hazards model for the emission of TPP at the place of residence of the mother and child, adjusted individual characteristics, demographic factors, and socioeconomic status related to the contextual level.

RESULTS

Infants born in areas with extremely high emission of TPP had a significantly higher risk of mortality due to respiratory diseases: hazard ratio (HR) = 1.781 [95% confidence interval (CI): 1.175, 2.697], p = 0.006, compared with those born in areas with the lowest emission levels. This effect was persistent when significant factors were adjusted at individual and contextual levels (HR = 1.959 [95% CI: 1.058, 3.628], p = 0.032). The increased risk of mortality was marked between the 50th and 150th days of life, coinciding with the highest exposure to TPP.

CONCLUSIONS

The emission of TPP from industries is associated with mortality due to respiratory diseases under one year of age. A considerable proportion of children's deaths could be prevented in Poland, especially in urban areas, if air pollution due to the emission of particle pollution is reduced.

Assessing whether genetic scores explain extra variation in birthweight, when added to clinical and anthropometric measures

BACKGROUND

Human birthweight is a complex, multifactorial trait. Maternal characteristics contribute to birthweight variation by influencing the intrauterine environment. Variation explained by genetic effects is also important, but their contributions have not been assessed alongside other key determinants. We aimed to investigate variance in birthweight explained by genetic scores in addition to easily-measurable clinical and anthropometric variables.

METHODS

We analysed 549 European-ancestry parent-offspring trios from a UK community-based birth cohort. We investigated variance explained in birthweight (adjusted for sex and gestational age) in multivariable linear regression models including genetic scores, routinely-measured maternal characteristics, and parental anthropometric variables. We used R-Squared (R²) to estimate variance explained, adjusted R-squared (Adj-R²) to assess improvement in model fit from added predictors, and F-tests to compare nested models.

RESULTS

Maternal and fetal genetic scores together explained 6.0% variance in birthweight. A model containing maternal age, weight, smoking, parity and 28-week fasting glucose explained 21.7% variance. Maternal genetic score explained additional variance when added to maternal characteristics (Adj-R² = 0.233 vs Adj-R² = 0.210, p < 0.001). Fetal genetic score improved variance explained (Adj-R² = 0.264 vs 0.248, p < 0.001) when added to maternal characteristics and parental heights.

CONCLUSIONS

Genetic scores account for variance explained in birthweight in addition to easily measurable clinical variables. Parental heights partially capture fetal genotype and its contribution to birthweight, but genetic scores explain additional variance. While the genetic contribution is modest, it is comparable to that of individual clinical characteristics such as parity, which suggests that genetics could be included in tools aiming to predict risk of high or low birthweights.

Prenatal exposure to air pollution and the risk of macrosomia: Identifying windows of susceptibility

This study explores the effects of prenatal exposure to air pollution on the risk of macrosomia and its window of susceptibility. We conducted a retrospective cohort study utilizing records of birth certificates for all full-term live newborns born in Xi'an city, China from January 1, 2015, to December 31, 2018.Weekly- and trimester-specific exposures of PM_2.5, PM₁₀, NO₂, and O₃ during pregnancy were calculated by inverse distance weighting (IDW) based on their residences. Cox proportional hazard model and distributed lag models (DLMs) were performed to estimate the effects of air pollution exposure during pregnancy on macrosomia risk and its window of susceptibility. In total, 318,323 full-term newborns were identified, including 24,996 (7.8%) cases of macrosomia. An IQR increase in PM_2.5 exposure (45.46 μg/m³) from the 33rd until the 37th weeks of gestation was positively associated with an elevated risk of macrosomia, with the strongest effect in the 37th weeks (HR = 1.007, 95%CI: 1.002-1.013). The window of susceptibility for NO₂ exposure on macrosomia risk was in the 29th-35th gestational weeks, with the strongest effect in the 34th weeks (IQR = 21.96 μg/m³, HR = 1.006, 95%CI:1.000-1.013). For prenatal exposure to O₃, 5th-24th weeks of gestation was identified as susceptible windows for elevated risk of macrosomia, with the strongest associations observed in the 15th weeks (IQR = 80.53 μg/m³, HR = 1.022, 95%CI: 1.011-1.033). However, we did not observe any associations between weekly exposure of PM₁₀ and macrosomia. Our findings imply that the windows of susceptibility to PM_2.5 and NO₂ exposure on macrosomia are mainly in late pregnancy, whereas the windows of susceptibility to O₃ exposure are in early and middle pregnancy.

Evolution of Lactase Persistence: Turbo-Charging Adaptation in Growth Under the Selective Pressure of Maternal Mortality?

The emergence of the capacity to digest milk in some populations represents a landmark in human evolution, linking genetic change with a component of niche construction, namely dairying. Alleles promoting continued activity of the enzyme lactase through the life-course (lactase persistence) evolved in several global regions within the last 7,000 years. In some European regions, these alleles underwent rapid selection and must have profoundly affected fertility or mortality. Elsewhere, alleles spread more locally. However, the functional benefits underlying the rapid spread of lactase persistence remain unclear. Here, we set out the hypothesis that lactase persistence promoted skeletal growth, thereby offering a generic rapid solution to childbirth complications arising from exposure to ecological change, or to new environments through migration. Since reduced maternal growth and greater neonatal size both increase the risk of obstructed labour, any ecological exposure impacting these traits may increase maternal mortality risk. Over many generations, maternal skeletal dimensions could adapt to new ecological conditions through genetic change. However, this adaptive strategy would fail if ecological change was rapid, including through migration into new niches. We propose that the combination of consuming milk and lactase persistence could have reduced maternal mortality by promoting growth of the pelvis after weaning, while high calcium intake would reduce risk of pelvic deformities. Our conceptual framework provides locally relevant hypotheses to explain selection for lactase persistence in different global regions. For any given diet and individual genotype, the combination of lactase persistence and milk consumption would divert more energy to skeletal growth, either increasing pelvic dimensions or buffering them from worsening ecological conditions. The emergence of lactase persistence among dairying populations could have helped early European farmers adapt rapidly to northern latitudes, East African pastoralists adapt to sudden climate shifts to drier environments, and Near Eastern populations counteract secular declines in height associated with early agriculture. In each case, we assume that lactase persistence accelerated the timescale over which maternal skeletal dimensions could change, thus promoting both maternal and offspring survival. Where lactase persistence did not emerge, birth weight was constrained at lower levels, and this contributes to contemporary variability in diabetes risk.

The role of genetics in fetal programming of adult cardiometabolic disease

Disturbances affecting early development have broad repercussions on the individual's health during infancy and adulthood. Multiple observational studies throughout the years have shown that alterations of fetal growth are associated with increased cardiometabolic disease risks. However, the genetic component of this association only started to be investigated in the last 40 years, when single genes with distinct effects were investigated. Birth weight (BW), commonly reported as the outcome of developmental growth, has been estimated to be 20% to 60% heritable. Through Genome-Wide Association (GWA) meta-analyses, 190 different loci have been identified being associated with BW, and while many of these loci designate genes involved in glucose and lipid metabolism, with clear ties to fetal development, the role of others is not yet understood. In addition, due to its influence over the intrauterine environment, the maternal genotype also plays an important part in the determination of offspring BW, with the same loci having independent effects of different magnitude or even direction. There is still much to uncover regarding the genetic determinants of BW and the interactions between maternal, offspring, and even paternal genotype. To fully understand these, diverse and novel cohorts from multiple ancestries collecting extensive neonatal phenotype will be needed. This review compiles, chronologically, the main findings in the investigation of the genetics of BW.

Genetics of early growth traits

In recent years, genome-wide association studies have shed light on the genetics of early growth and its links with later-life health outcomes. Large-scale datasets and meta-analyses, combined with recently developed analytical methods, have enabled dissection of the maternal and fetal genetic contributions to variation in birth weight. Additionally, longitudinal approaches have shown differences between the genetic contributions to infant, childhood and adult adiposity. In contrast, studies of adult height loci have shown strong associations with early body length and childhood height. Early growth-associated loci provide useful tools for causal analyses: Mendelian randomization (MR) studies have provided evidence that early BMI and height are causally related to a number of adult health outcomes. We advise caution in the design and interpretation of MR studies of birth weight investigating effects of fetal growth on later-life cardiometabolic disease because birth weight is only a crude indicator of fetal growth, and the choice of genetic instrument (maternal or fetal) will greatly influence the interpretation of the results. Most genetic studies of early growth have to date centered on European-ancestry participants and outcomes measured at a single time-point, so key priorities for future studies of early growth genetics are aggregation of large samples of diverse ancestries and longitudinal studies of growth trajectories.

A multi-omic analysis of birthweight in newborn cord blood reveals new underlying mechanisms related to cholesterol metabolism

BACKGROUND

Birthweight reflects in utero exposures and later health evolution. Despite existing studies employing high-dimensional molecular measurements, the understanding of underlying mechanisms of birthweight remains limited.

METHODS

To investigate the systems biology of birthweight, we cross-sectionally integrated the methylome, the transcriptome, the metabolome and a set of inflammatory proteins measured in cord blood samples, collected from four birth-cohorts (n = 489). We focused on two sets of 68 metabolites and 903 CpGs previously related to birthweight and investigated the correlation structures existing between these two sets and all other omic features via bipartite Pearson correlations.

RESULTS

This dataset revealed that the set of metabolome and methylome signatures of birthweight have seven signals in common, including three metabolites [PC(34:2), plasmalogen PC(36:4)/PC(O-36:5), and a compound with m/z of 781.0545], two CpGs (on the DHCR24 and SC4MOL gene), and two proteins (periostin and CCL22). CCL22, a macrophage-derived chemokine has not been previously identified in relation to birthweight. Since the results of the omics integration indicated the central role of cholesterol metabolism, we explored the association of cholesterol levels in cord blood with birthweight in the ENVIRONAGE cohort (n = 1097), finding that higher birthweight was associated with increased high-density lipoprotein cholesterol and that high-density lipoprotein cholesterol was lower in small versus large for gestational age newborns.

CONCLUSIONS

Our data suggests that an integration of different omic-layers in addition to single omics studies is a useful approach to generate new hypotheses regarding biological mechanisms. CCL22 and cholesterol metabolism in cord blood play a mechanistic role in birthweight.

Growth patterns and associated risk factors of congenital malformations in twins

BACKGROUND

The rate of twinning continues to increase due to the combined effect of a rise in parental age and increased use of assisted reproductive technology. The risk of congenital anomalies in twins is higher than in singletons, but it is less well reported in relation to growth patterns. We focused to the auxological outcome of twin pregnancies when one or both of twins are affected by one or more malformations.

METHODS

We conducted a retrospective observational study reviewing the clinical charts of twins admitted in the period between January 2003 and December 2018 at the University Hospital of Palermo. The associations between malformations and anthropometric variables at birth were analyzed by comparison within each twin pair and regarding each variable as ordered difference between the two twins.

RESULTS

We studied data of 488 neonates (52% females) from 244 pregnancies. The rate of major congenital anomalies was 11%, affecting significantly the smaller twin (p = .00018; Odds ratio 3.21; 95% CI 1.65 6.59). Malformation class distribution was as following: genitourinary (24%), gastrointestinal (20%), cardiovascular (18.5%), musculoskeletal (11%), central nervous system (9%), syndromic (9%), ocular (5.5%) and diaphragmatic hernia (2%). The most predictive value, the Birthweight (BW) difference mean ratio in malformed versus not malformed neonates (- 0.31 vs 0.02; p = .0016) was distributed equally lower than zero in all malformed twins, except for those with congenital heart defects (p = .0000083). Microcephaly (head circumference < 2 standard deviation, SD) was present in 3% of symmetrically smaller twin, and severe microcephaly (< 3 SD) was present in 0.6%. We found that an intertwin BW discordance of 18% or greater identified 50% of neonates with microcephaly, but only 11% of malformed twins.

CONCLUSIONS

In case of one twin with a BW < 10th centile, a concomitant intertwin BW discordance ≥18% could reveal an increased risk for microcephaly but not for malformation. Lower values of BW, Ponderal index, Body mass index but above all negative value of BW difference mean ratio are associated with malformations in twin pairs.

Delayed neonatal visual evoked potentials are associated to asymmetric growth pattern in twins

OBJECTIVES

To study the association between intrauterine growth and visual pathways maturation by neonatal visual evoked potentials (VEPs) in twins, in view of a possible prognostic role.

METHODS

Seventy-four twin neonates from 37 pregnancies were selected based on gestational age of more than 30 weeks and uneventful perinatal clinical course. Flash VEPs were recorded at the same postmenstrual age in each twin pair. The association between P2 latency and anthropometric variables at birth was analyzed by comparison within each twin pair and regarding each variable as ordered difference between the two twins.

RESULTS

Analysis of differences within each twin pair highlighted that inter-twin difference in P2 latency was significantly related to difference in ponderal index (PI) (p = 0.048). Expressing the difference in latency as a categorical binary variable, the correlation was significant for both difference in PI, (median difference = -0.36, 95% CI -0.54 to -0.14, p = 0.001) and difference in body mass index (BMI), (median difference = -1.06, 95% CI -1.74 to -0.29, p = 0.006).

CONCLUSIONS

Lower values of PI and BMI differences are associated to delayed VEP latency in twin pairs.

SIGNIFICANCE

VEP latency suggests reduced myelination of visual pathways when difference in growth pattern occurs in twins.

THE EXPOSOME IN HUMAN EVOLUTION: FROM DUST TO DIESEL

Global exposures to air pollution and cigarette smoke are novel in human evolutionary history and are associated with about 16 million premature deaths per year. We investigate the history of the human exposome for relationships between novel environmental toxins and genetic changes during human evolution in six phases. Phase I: With increased walking on savannas, early human ancestors inhaled crustal dust, fecal aerosols, and spores; carrion scavenging introduced new infectious pathogens. Phase II: Domestic fire exposed early Homo to novel toxins from smoke and cooking. Phases III and IV: Neolithic to preindustrial Homo sapiens incurred infectious pathogens from domestic animals and dense communities with limited sanitation. Phase V: Industrialization introduced novel toxins from fossil fuels, industrial chemicals, and tobacco at the same time infectious pathogens were diminishing. Thereby, pathogen-driven causes of mortality were replaced by chronic diseases driven by sterile inflammogens, exogenous and endogenous. Phase VI: Considers future health during global warming with increased air pollution and infections. We hypothesize that adaptation to some ancient toxins persists in genetic variations associated with inflammation and longevity.

The New West Japan Twins and Higher Order Multiple Births Registry

The new West Japan Twins and Higher Order Multiple Births Registry was established by recruiting young twins and multiple births and by referrals from public health centers in the 1990s. The participants included in the survey comprised over 7800 twins and 4241 higher order multiples, and their families. Specifically, the present registry contains one of the largest triplet samples in the world. For these twins and multiples, data on year of delivery, mode of delivery, gestational age, intrapartum complications, longitudinal physical measures, motor milestones, cerebral palsy and feeding methods were obtained from records in the Maternal and Child Health Handbooks and schools. Participating mothers were asked to indicate family structure, parental educational history, maternal sleeping time, maternal health condition, maternal and paternal age at multiple delivery, complications during pregnancy, handedness of multiples and age at menarche of multiples. However, the zygosity differed among the various collaborating public health centers according to factors such as the time of investigation. Follow-up questionnaires have been mailed out every 3-4 years for longitudinal studies. This article describes the goals of this registry, recruitment of multiples and the focus of the study. The goals of this registry are not only to conduct research on human genetics and maternal and child health, but also to contribute to providing appropriate information for families with multiples.

The CODATwins Project: The Current Status and Recent Findings of COllaborative Project of Development of Anthropometrical Measures in Twins

The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m2) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and length, own smoking behavior and own or parental education. We found that the heritability estimates of height and BMI systematically changed from infancy to old age. Remarkably, only minor differences in the heritability estimates were found across cultural-geographic regions, measurement time and birth cohort for height and BMI. In addition to genetic epidemiological studies, we looked at associations of height and BMI with education, birth weight and smoking status. Within-family analyses examined differences within same-sex and opposite-sex dizygotic twins in birth size and later development. The CODATwins project demonstrates the feasibility and value of international collaboration to address gene-by-exposure interactions that require large sample sizes and address the effects of different exposures across time, geographical regions and socioeconomic status.

Genetic insights into fetal growth and measures of glycaemic regulation and adiposity in adulthood: a family-based study

Background

The genetics of fetal insulin release and/or action have been suggested to affect fetal growth, adult insulin resistance and adult body composition. The genetic correlation between body composition at birth versus glycaemic regulation and body composition in adulthood have, however, not been well studied. We therefore aimed to investigate these genetic correlations in a family-based cohort.

Methods

A Danish family cohort of 434 individuals underwent an oral glucose tolerance test with subsequent calculation of surrogate measures of serum insulin response and insulin sensitivity. Measures of fetal growth were retrieved from midwife journals. Heritability and genetic correlations were estimated using a variance component model.

Results

A high heritability of 0.80 was found for birth weight, whereas ponderal index had a heritability of 0.46. Adult insulin sensitivity measured as Matsuda index was genetically correlated with both birth weight and ponderal index (ρG = 0.36 (95% CI: 0.03; 0.69) and ρG = 0.52 (95% CI, 0.15; 0.89), respectively). Only birth weight showed a significant genetic correlation with adult weight (ρG = 0.38 (95% CI: 0.09; 0.67)) whereas only ponderal index was genetically inversely correlated with fasting insulin (ρG = - 0.47 (95% CI: - 0.86; - 0.08) and area under the curve for insulin release during the oral glucose tolerance test (ρG = - 0.66 (95% CI: - 1.13; - 0.19)).

Individual as well as combined adjustment for 45 selected birth weight, obesity and type 2 diabetes susceptibility gene variants did not affect the correlations.

Conclusions

The genetics of both birth weight and ponderal index appear to be under the same genetic influence as adult insulin resistance. Furthermore, ponderal index and adult insulin release seem to be partly shared, as well as the genetics of birth weight and adult weight.

Word count abstract: 281.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0718-2) contains supplementary material, which is available to authorized users.