Mother's and father's birthweight as predictors of infant birthweight

The impact of maternal and paternal birth weights on infant birth weights: the Japan environment and children's study

This study aimed to evaluate the association between parental and infant birth weights in Japan. In total, 37,504 pregnant Japanese women and their partners were included in this birth cohort study. A multinomial logistic regression model was used to evaluate the associations of parental birth weights with small-for-gestational-age (SGA) or large-for-gestational-age (LGA) infants. Associations between parental birth weight and low birth weight (LBW) infants or macrosomia were also examined, and linear associations between parental birth weight and SGA or LGA were found. The adjusted odds ratios (aORs) for SGA infants per 500 g decrease in maternal and paternal birth weights were 1.50 (95% confidence interval [CI],1.43-1.58) and 1.31 (95% CI, 1.25-1.38), respectively. The aORs for LGA infants per 500 g increase in maternal and paternal birth weights were 1.53 (95% CI, 1.47-1.60) and 1.41 (95% CI, 1.35-1.47), respectively. The association between parental birth weight and LBW infants or macrosomia was also linear. The aORs for LBW infants per 500 g decrease in maternal and paternal birth weights were 1.47 (95% CI, 1.40-1.55) and 1.25 (95% CI, 1.19-1.31), respectively. The aORs for macrosomia per 500 g increase in maternal and paternal birth weights were 1.59 (95% CI, 1.41-1.79) and 1.40 (95% CI, 1.23-1.60), respectively. Parental birth weight was found to be associated with infant birth weight even after adjusting for various parental factors. Furthermore, maternal birth weight was more strongly associated with infant birth weight than with paternal birth weight.

Intergenerational transmission of birth weight: a systematic review and meta-analysis

The objectives of this study were (1) to systematically review the literature on the association between birth weight in children born in the first and second generation and (2) to quantify this association by performing a meta-analysis. A systematic review was carried out in six databases (PubMed, Science Direct, Web of Science, Embase, Scopus, CINAHL and LILACS), in January 2021, for studies that recorded the birth weight of parents and children. A meta-analysis using random effects to obtain a pooled effect of the difference in birth weight and the association of low birth weight (LBW) between generations was performed. Furthermore, univariable meta-regression was conducted to assess heterogeneity. Egger's tests were used to possible publication biases. Of the 9878 identified studies, seventy were read in full and twenty were included in the meta-analysis (ten prospective cohorts and ten retrospective cohorts), fourteen studies for difference in means and eleven studies for the association of LBW between generations (twenty-three estimates). Across all studies, there was no statistically significant mean difference (MD) birth weight between first and second generation (MD 19·26, 95 % CI 28·85, 67·36; P = 0·43). Overall, children of LBW parents were 69 % more likely to have LBW (pooled effect size 1·69, 95 % CI (1·46, 1·95); I2:85·8 %). No source of heterogeneity was identified among the studies and no publication bias. The average birth weight of parents does not influence the average birth weight of children; however, the proportion of LBW among the parents seems to affect the offspring's birth weight.

Relationships of maternal and paternal anthropometry with neonatal body size, proportions and adiposity in an Australian cohort

The patterns of association between maternal or paternal and neonatal phenotype may offer insight into how neonatal characteristics are shaped by evolutionary processes, such as conflicting parental interests in fetal investment and obstetric constraints. Paternal interests are theoretically served by maximizing fetal growth, and maternal interests by managing investment in current and future offspring, but whether paternal and maternal influences act on different components of overall size is unknown. We tested whether parents' prepregnancy height and body mass index (BMI) were related to neonatal anthropometry (birthweight, head circumference, absolute and proportional limb segment and trunk lengths, subcutaneous fat) among 1,041 Australian neonates using stepwise linear regression. Maternal and paternal height and maternal BMI were associated with birthweight. Paternal height related to offspring forearm and lower leg lengths, maternal height and BMI to neonatal head circumference, and maternal BMI to offspring adiposity. Principal components analysis identified three components of variability reflecting neonatal “head and trunk skeletal size,” “adiposity,” and “limb lengths.” Regression analyses of the component scores supported the associations of head and trunk size or adiposity with maternal anthropometry, and limb lengths with paternal anthropometry. Our results suggest that while neonatal fatness reflects environmental conditions (maternal physiology), head circumference and limb and trunk lengths show differing associations with parental anthropometry. These patterns may reflect genetics, parental imprinting and environmental influences in a manner consistent with parental conflicts of interest. Paternal height may relate to neonatal limb length as a means of increasing fetal growth without exacerbating the risk of obstetric complications. Am J Phys Anthropol 156:625–636, 2015.

Maternal predictors of neonatal bone size and geometry: the Southampton Women's Survey

Early growth is associated with later risk of osteoporosis and fractures. In this study, we aimed to evaluate the relationships between maternal lifestyle and body composition and neonatal bone size, geometry and density in the offspring. Participants were recruited from the Southampton Women's Survey, a unique prospective cohort of 12,500 initially non-pregnant women aged 20-34 years, resident in Southampton, UK. These women were studied in detail before and during pregnancy, and the offspring underwent anthropometric and bone mineral assessment (using dual energy-X-ray absorptiometry) at birth. A total of 841 mother-baby pairs were studied (443 boys and 398 girls). The independent predictors of greater neonatal whole body bone area (BA) and bone mineral content included greater maternal birthweight, height, parity, triceps skinfold thickness and lower walking speed in late pregnancy. Maternal smoking was independently associated with lower neonatal bone mass. Neonatal BA adjusted for birth length (a measure of bone width) was predicted positively by maternal parity and late pregnancy triceps skinfold thickness and negatively by late pregnancy walking speed. These findings were similar in both genders. We have confirmed, in a large cohort, previous findings that maternal lifestyle and body build predict neonatal bone mineral; additionally, maternal parity and fat stores and walking speed in late pregnancy were associated with neonatal bone geometry. These findings may suggest novel public health strategies to reduce the burden of osteoporotic fracture in future generations.

Influence of maternal and paternal birthweight on offspring birthweight - a population-based intergenerational study

BACKGROUND

The correlation between infant birthweight and parental birthweight has received substantial interest. However, fewer studies including the birthweight of the father have had access to large sets of population-based data. The objective of this study is to examine the influence of maternal and paternal birthweight on the birthweight of the offspring in the context of other birthweight determinants, with a special focus on the contribution of paternal birthweight.

METHODS

The data used were retrieved from the Swedish Population Register, Medical Birth Register and Multi-Generation Register. Full-term, singleton births were included and linked through personal ID numbers given to every resident at birth, forming 137 538 mother-father-child units with valid birthweights. The analyses were made through linear regression models.

RESULTS

The positive association for both maternal and paternal birthweight remained after introducing other determinants in the model, yielding a difference in offspring birthweight by 164 g [95% confidence interval 159, 170] and 149 g [95% confidence interval 145, 154] for every 1000 g rise in birthweight of the mother and father respectively. Maternal birthweight explained 6% of the variance in birthweight, whereas paternal birthweight explained 3%. There was no difference when analyses were stratified according to gender.

CONCLUSION

These results suggest that maternal and paternal birthweight remain relevant for infant birthweight, even after consideration of other determinants of birthweight.

Maternal Prenatal Nutrition and Health in Grandchildren and Subsequent Generations

This review focuses on how maternal prenatal nutritional states may affect the health of grandchildren and later generations. We first summarize the limited current data in human populations relating to the potential transmission of phenotypes across multiple generations that result from the nutritional experience of a pregnant woman. We then discuss findings from other species, especially mammals, that provide important clues as to whether, and if so how, such transmission could occur in humans. Finally, we consider how studies of human populations could be best designed to detect transmission across multiple generations. We argue that just as epidemiologists embraced a life-course perspective to human health and disease in the twentieth century, we must now seek to better understand how health and disease could be shaped across multiple generations.

Intergenerational influences on child growth and undernutrition

Intergenerational effects on linear growth are well documented. Several generations are necessary in animal models to 'wash out' effects of undernutrition, consistent with the unfolding of the secular trend in height in Europe and North America. Birthweight is correlated across generations and short maternal stature, which reflects intrauterine and infant growth failure, is associated with low birthweight, child stunting, delivery complications and increased child mortality, even after adjusting for socio-economic status. A nutrition intervention in Guatemala reduced childhood stunting; it also improved growth of the next generation, but only in the offspring of girls. Possible mechanisms explaining intergenerational effects on linear growth are not mutually exclusive and include, among others, shared genetic characteristics, epigenetic effects, programming of metabolic changes, and the mechanics of a reduced space for the fetus to grow. There are also socio-cultural factors at play that are important such as the intergenerational transmission of poverty and the fear of birthing a large baby, which leads to 'eating down' during pregnancy. It is not clear whether there is an upper limit for impact on intrauterine and infant linear growth that programmes in developing countries could achieve that is set by early childhood malnutrition in the mother. Substantial improvements in linear growth can be achieved through adoption and migration, and in a few selected countries, following rapid economic and social development. It would seem, despite clear documentation of intergenerational effects, that nearly normal lengths can be achieved in children born to mothers who were malnourished in childhood when profound improvements in health, nutrition and the environment take place before conception. To achieve similar levels of impact through public health programmes alone in poor countries is highly unlikely. The reality in poor countries limits the scope, quality and coverage of programmes that can be implemented and modest impact should be expected instead. The Lancet series on Maternal and Child Undernutrition estimated that implementation to scale of proven interventions in high burden countries would reduce stunting by one-third; this is perhaps a realistic upper bound for impact for high quality programmes, unless accompanied by sweeping improvements in social services and marked reductions in poverty. Finally, because so much can be achieved in a single generation, intergenerational influences are unlikely to be an important explanation for lack of programme impact aimed at the window of the first 1000 days. Failure to prevent linear growth failure in developing countries has serious consequences for short- and long-term health as well as for the formation of human capital. The nutrition transition has created a double burden by adding obesity and related chronic diseases to the public health agenda of countries still struggling with the 'old' problems of maternal and child undernutrition. The challenge ahead is to increase efforts to prevent linear growth failure while keeping child overweight at bay.

Genetic and Non-Genetic Factors Affecting Birth-Weight and Adult Body Mass Index

Birthweight affects neonatal mortality and morbidity and has been used as a marker of foetal undernutrition in studies of prenatal effects on adult characteristics. It is potentially influenced by genetic and environmental influences on the mother, and effects of foetal genotype, which is partially derived from the maternal genotype. Interpretations of variation in birthweight and associated characteristics as being due to prenatal environment ignore other possible modes of materno-foetal transmission. Subjects were adult twins recruited through the Australian Twin Registry, aged 17 to 87 years, and the sample comprised 1820 men and 4048 women. Twins reported their own birthweight as part of a health questionnaire. Body Mass Index (BMI) was calculated from self-reports of height and weight. Correlations between co-twins' birthweights were high for both monozygotic (r = 0.77) and dizygotic (r = 0.67) pairs, leading to substantial estimates of shared environmental effects (56% of variance) with significant additive genetic (23%) and non-shared environmental (21%) components. Adult BMI was mainly influenced by genetic factors, both additive (36% of variance) and nonadditive (35%). The correlation between birthweight and BMI was positive, in that heavier babies became on average more obese adults. A bivariate model of birthweight and adult BMI showed significant positive genetic (rg = 0.16, p = 0.005) and environmental (re = 0.08, p = 0.000011) correlations. Intra-uterine environmental or perinatal influences shared by cotwins exercise a strong influence on birthweight, but the factors which affect both birthweight and adult BMI are partly genetic and partly non-shared environmental.

Intrauterine growth and postnatal skeletal development: findings from the Southampton Women's Survey

We have previously demonstrated associations between fetal growth in late pregnancy and postnatal bone mass. However, the relationships between the intrauterine and early postnatal skeletal growth trajectory remain unknown. We addressed this in a large population-based mother-offspring cohort study. A total of 628 mother-offspring pairs were recruited from the Southampton Women's Survey. Fetal abdominal circumference was measured at 11, 19 and 34 weeks gestation using high-resolution ultrasound with femur length assessed at 19 and 34 weeks. Bone mineral content was measured postnatally in the offspring using dual-energy X-ray absorptiometry at birth and 4 years; postnatal linear growth was assessed at birth, 6, 12, 24, 36 and 48 months. Late pregnancy abdominal circumference growth (19-34 weeks) was strongly (P < 0.01) related to bone mass at birth, but less robustly associated with bone mass at 4 years. Early pregnancy growth (11-19 weeks) was more strongly related to bone mass at 4 years than at birth. Postnatal relationships between growth and skeletal indices at 4 years were stronger for the first and second postnatal years, than the period aged 2-4 years. The proportion of children changing their place in the distribution of growth velocities progressively reduced with each year of postnatal life. The late intrauterine growth trajectory is a better predictor of skeletal growth and mineralisation at birth, while the early intrauterine growth trajectory is a more powerful determinant of skeletal status at age 4 years. The perturbations in this trajectory which influence childhood bone mass warrant further research.

Intergenerational correlations in size at birth and the contribution of environmental factors: The Uppsala Birth Cohort Multigenerational Study, Sweden, 1915-2002

Sizes at birth of parents and their children are known to be correlated, reflecting in part the influence of fetal and maternal genes. Sociodemographic factors, regarded as aspects of the shared environment across generations, would also be expected to contribute, but evidence is limited. In the present study, the authors aimed to quantify the role of the shared environment in explaining intergenerational correlations in birth weight and length by using data across 3 consecutive generations from the Uppsala Birth Cohort Multigenerational Study in Uppsala, Sweden. That study included birth and sociodemographic data on 7,657 singletons born in Uppsala in 1915-1929 (generation 1) and their grandchildren (generation 3). Standard regression and biometric models were used to study the correlations in size at birth of generation 1-generation 3 pairs. The data showed stronger correlations in maternal pairs than in paternal pairs for birth weight (0.125 vs. 0.096, P = 0.02) but not for birth length (0.097 vs. 0.093, P = 0.77). These correlations were not reduced by adjustment for sociodemographic factors in regression models. In contrast, significant shared-environment contributions to the intergenerational correlations were identified in biometric models, averaging 14% for both birth measures. These models assumed a common latent factor for the sociodemographic variables. The present results show that the shared environment moderately but significantly contributes to intergenerational correlations.

Maternal vitamin D receptor genetic variation contributes to infant birthweight among black mothers

Racial disparity in pregnancy outcomes is one of the most striking and poorly understood inequalities in American health. Genetic variability may be an important host factor influencing disparate birth outcomes between non-Hispanic black (NHB) and non-Hispanic white (NHW) women. Race-specific allelic frequencies in the vitamin D receptor (VDR) gene suggest its potential as a gene involved in health disparities. The Healthy Pregnancy, Healthy Baby Study is a prospective cohort of pregnant women aimed at identifying genetic, social, and environmental contributors to disparities in pregnancy outcomes in Durham, NC. VDR haplotype tagging single nucleotide polymorphisms (SNPs) were genotyped via Taqman assays for 615 women. Analysis of variance was used to examine the association between maternal genotype and infant birthweight. Eight of 38 SNPs examined showed nominal significance among NHB women, with one VDR SNP (rs7975232) surpassing the multiple testing significance threshold. rs7975232, an anonymous polymorphism, is part of a VDR gene haplotype associated with variation in mRNA stability. mRNA stability can affect the amount of protein produced, thus directly affecting vitamin D levels and calcium homeostasis. In contrast to NHBs, there was no association between any VDR SNP and birthweight for NHWs. Genetic factors contributing to disparities in birth outcomes are not expected to be explained entirely by variation in a single gene. Nevertheless, our results suggest that maternal VDR gene polymorphisms do influence birthweight with differential effects accruing across racial groups. Further research identifying the functionality of VDR gene polymorphisms in pregnant women will improve our understanding of the underlying mechanisms influencing birthweight.

Epigenetics and the origins of paternal effects

Though there are multiple routes through which parents can influence their offspring, recent studies of environmentally induced epigenetic variation have highlighted the role of non-genomic pathways. In addition to the experience-dependent modification of DNA methylation that can be achieved via mother-infant interactions, there has been increasing interest in the epigenetic mechanisms through which paternal influences on offspring development can be achieved. Epidemiological and laboratory studies suggest that paternal nutritional and toxicological exposures as well as paternal age and phenotypic variation can lead to variations in offspring and, in some cases, grand-offspring development. These findings suggest a potential epigenetic germline inheritance of paternal effects. However, it may be important to consider the interplay between maternal and paternal influences as well as the experimental dissociation between experience-dependent and germline transmission when exploring the role of epigenetic variation within the germline as a mediator of these effects. In this review, we will explore these issues, with a particular focus on the potential role of paternally induced maternal investment, highlight the literature illustrating the transgenerational impact of paternal experiences, and discuss the evidence supporting the role of epigenetic mechanisms in maintaining paternal effects both within and across generations.

Parental factors affecting the weights of the placenta and the offspring

AIM

To determine parental, especially paternal factors associated with the weight of the placenta and offspring.

METHODS

This population-based birth-cohort study includes 2947 singleton children born from April 2006 to 2007 and living in Drenthe, The Netherlands. Placental weight and birth weight were measured and questionnaires were filled out for this cohort. Associations between parental factors, and the weight of the placenta and the offspring were evaluated using univariate and multivariate linear regression models.

RESULTS

Univariate regression revealed that the paternal birth weight and body mass index (BMI) of the father were predictors for placental and birth weight of the offspring. However, they were not independent predictors. Independent predictors for placental weight were the maternal factors of pre-pregnancy BMI, birth weight, and diabetes. The maternal factors of weight gain during pregnancy, birth weight, smoking during pregnancy, and diabetes were independent predictors for birth weight of the offspring.

CONCLUSION

Paternal as well as maternal factors influence the weight of the placenta and the offspring.

Different indices of fetal growth predict bone size and volumetric density at 4 years of age

We have demonstrated previously that higher birth weight is associated with greater peak and later-life bone mineral content and that maternal body build, diet, and lifestyle influence prenatal bone mineral accrual. To examine prenatal influences on bone health further, we related ultrasound measures of fetal growth to childhood bone size and density. We derived Z-scores for fetal femur length and abdominal circumference and conditional growth velocity from 19 to 34 weeks' gestation from ultrasound measurements in participants in the Southampton Women's Survey. A total of 380 of the offspring underwent dual-energy X-ray absorptiometry (DXA) at age 4 years [whole body minus head bone area (BA), bone mineral content (BMC), areal bone mineral density (aBMD), and estimated volumetric BMD (vBMD)]. Volumetric bone mineral density was estimated using BMC adjusted for BA, height, and weight. A higher velocity of 19- to 34-week fetal femur growth was strongly associated with greater childhood skeletal size (BA: r = 0.30, p < .0001) but not with volumetric density (vBMD: r = 0.03, p = .51). Conversely, a higher velocity of 19- to 34-week fetal abdominal growth was associated with greater childhood volumetric density (vBMD: r = 0.15, p = .004) but not with skeletal size (BA: r = 0.06, p = .21). Both fetal measurements were positively associated with BMC and aBMD, indices influenced by both size and density. The velocity of fetal femur length growth from 19 to 34 weeks' gestation predicted childhood skeletal size at age 4 years, whereas the velocity of abdominal growth (a measure of liver volume and adiposity) predicted volumetric density. These results suggest a discordance between influences on skeletal size and volumetric density.

Paternal factors and low birthweight, preterm, and small for gestational age births: a systematic review

A systematic review of the risks of a low birthweight (LBW), preterm, and small-for-gestational-age births in relation to paternal factors was performed. Medline, Embase, Cumulative Index of Nursing and Allied Health Literature, and bibliographies of identified articles were searched for English-language studies. Study qualities were assessed according to a predefined checklist. Thirty-six studies of low-to-moderate risk of bias were reviewed for various paternal factors: age, height, weight, birthweight, occupation, education, and alcohol use. Extreme paternal age was associated with higher risk for LBW. Among infants who were born to tall fathers, birthweight was approximately 125-150 g higher compared with infants who were born to short fathers. Paternal LBW was associated with lower birthweight of the offspring. In conclusion, paternal characteristics including age, height, and birthweight are associated with LBW. Paternal occupational exposure and low levels of education may be associated with LBW; however, further studies are needed.

Intergenerational effect of weight gain in childhood on offspring birthweight

Background Some studies suggest that weight gain in childhood may increase the risk of chronic diseases in adulthood, and recent studies have noticed that the timing of weight gain may be related to its long-term consequence. However, weight gain in childhood has clear short-term benefits, and the literature on the pro and cons of weight gain in childhood is limited.

Methods In 1982, all 5914 hospital births (over 99% of all deliveries) occurring in Pelotas, Southern Brazil, were identified and studied prospectively on several occasions. In 2004–05, we attempted to trace the whole cohort and information on offspring birthweight was collected. Conditional growth modelling was used to assess the association between offspring birthweight and weight gain from birth to 20 months, and from 20 to 42 months.

Results In 2004–05, we interviewed 4297 subjects, with a follow-up rate of 77.4%. This manuscript includes data from 848 women who had already delivered a child and 525 men who were fathers at the mean age of 23 years. Maternal birthweight, weight and length for age Z-score at 20 months of age were positively associated with next-generation birthweight, whereas paternal variables were not related to the outcome. Conditional growth modelling analyses showed that women whose weight gain in the first 20 months of life was faster than predicted had heavier babies, whereas paternal weight gain was not associated. The association was strongest for mothers whose birthweight for gestational age was in the lowest tertile.

Conclusion Maternal, but not paternal birthweight and weight gain in early childhood are positively associated with next-generation birthweight.

Cardiovascular risk factors in parents of short children born small for gestational age

Small for gestational age (SGA) children have a higher prevalence of cardiovascular risk factors at a young age. It is not known whether this increased risk is caused by their size at birth, a familial predisposition for cardiovascular disease or smallness at birth or a combination of these factors. The cardiovascular risk profile of parents of SGA children is unknown. We compared anthropometry, blood pressure, fasting serum lipid, glucose, and insulin levels of 482 parents (mean age 41 y) and 286 short SGA children with age- and sex-matched references. We also investigated whether these parameters correlated between parents and their offspring. Mothers had higher systolic blood pressure, fathers had a higher body mass index and parents had more frequently high fasting glucose levels than age- and sex-matched references. Children had significantly higher systolic and diastolic blood pressure than sex- and height-matched references. Twenty-four percent (mothers) and 10% (fathers) were born SGA but they did not have more cardiovascular risk factors than those born appropriate for gestational age. Cardiovascular risk factors did not correlate between parents and children. In conclusion, parents of short SGA children have a modest increase in some cardiovascular risk factors but risk factors did not correlate between parents and children.

Paternal skeletal size predicts intrauterine bone mineral accrual

BACKGROUND

We have previously demonstrated that maternal body build and lifestyle factors predict neonatal bone mineral accrual. However, the paternal determinants of neonatal bone mass are not known. In this study we explored the relationship between a father's bone mass and that of his offspring.

METHODS

A total of 278 pregnancies (142 male and 136 female neonates) were recruited from the Southampton Women's Survey, a unique, well-established cohort of women, aged 20-34 yr, who had been assessed before and during pregnancy. The neonates and their fathers underwent whole body dual-x-ray absorptiometry (DXA) within 2 wk of birth using a Lunar DPX (General Electric Corp., Madison, WI) and Hologic Discovery instrument (Hologic Inc., Bedford, MA), respectively; correlation and regression methods were used to explore the parental determinants of neonatal bone mass.

RESULTS

After adjusting the paternal DXA indices for father's age and the neonatal for baby's gestational age and age at DXA scan, there were highly significant positive associations between baby's whole body bone area, bone mineral content, and bone mineral density and the corresponding indices in the father (P = 0.003, 0.0002, 0.046, respectively) among female infants. These relationships were independent of maternal height and fat stores. The associations for male infants with paternal DXA indices did not achieve statistical significance.

CONCLUSIONS

The father's skeletal size predicts skeletal size more strongly in female than male offspring, independently of the mother's body build. These data point toward the importance of considering paternal genotype in studies exploring the developmental origins of osteoporotic fracture and raise intriguing mechanistic questions about the gender specificity of influences on intrauterine bone mineral accrual.

Trends in human birth weight across two successive generations

OBJECTIVE

To determine the correlation between parental and offspring birthweight (BW) in India.

METHODS

The study involved two birth cohorts of successive generations. The parental cohort comprised of 472 fathers and 422 mothers from an earlier study. Details of their anthropometry at birth and in adulthood were available. 1525 children born to them comprised the offspring cohort. BW was obtained from hospital records for the offspring cohort. Odds ratios and regression coefficients were calculated to estimate the risks of a low birth weight (LBW) parent producing a LBW baby and quantitate the effects after adjusting for confounders.

RESULTS

A LBW mother had a 2.8 times risk (95%CI 1.2-6.4) of delivering a LBW baby (p=0.02) and a LBW father was twice as likely to produce a LBW baby (OR 2.2; 95%CI 1.0 - 4.8; p=0.05). Every 100g increase in maternal BW was associated with an increase in offspring BW of 14 g; the equivalent figure for paternal BW was 18.1g (p< 0.001 for both). Between the generations, the incidence of LBW decreased from 19.7% to 17.2% (p=0.1). Mean BW increased in males (2846 g vs 2861 g; p=0.59) but not in females (2790 g vs 2743 g; p=0.08).

CONCLUSION

Both maternal and paternal BW are strong determinants of offspring BW. The effect of mothers' BW on offspring BW is weaker than that seen in developed nations. Stronger intrauterine constraint exhibited by Indian women secondary to a higher prevalence of growth restriction in utero may be responsible. Paternal effects may be governed by paternal genes inherited by the offspring.

Placental calcium transporter (PMCA3) gene expression predicts intrauterine bone mineral accrual

Evidence is accruing that environmental exposures during critical periods of early development induce persisting changes in skeletal growth, and alter fracture risk in later life. We have previously demonstrated that placental calcium transport, partly determined by maternal 25-(OH) vitamin D status, may underlie this phenomenon. However, the precise relationship between expression of calcium transport proteins in the human placenta, and neonatal bone mineral accrual in the offspring, remains unknown. Tissue samples from 70 human placentae were fast frozen in liquid nitrogen and stored at -70 degrees C. A quantitative real time reverse transcriptase polymerase chain reaction was used to measure the mRNA expression of PMCA isoforms 1-4, using beta-actin as a control gene. Neonatal whole body bone area, mineral content and areal density (BA, BMC, BMD) were measured within 2 weeks of birth using DXA. PMCA3 mRNA expression predicted BA (r=0.28, p=0.02), BMC (r=0.25, p=0.04), placental weight (r=0.26, p=0.04) and birth weight (r=0.33, p=0.006) of the neonate. In a multivariate model, the relationship between placental PMCA3 expression and neonatal BMC was independent of maternal height, pre-pregnant fat stores, parity, physical activity, smoking, and calcium intake (p<0.05). Expression of the placental calcium transporter PMCA3 mRNA predicts neonatal whole body bone mineral content. This association may explain, in part, the mechanism whereby a mother's 25(OH)-vitamin D stores influence her offspring's bone mass.

Females born large for gestational age have a doubled risk of giving birth to large for gestational age infants

AIM

To analyse if females born large for gestational age (LGA) have an increased risk to give birth to LGA infants and to study anthropometric characteristics in macrosomic infants of females born LGA.

METHODS

The investigation was performed as an intergenerational retrospective study of women born between 1973 and 1983, who delivered their first infant between 1989 and 1999. Birth characteristics of 47,783 females, included in the Swedish Birth Register both as newborns and mothers were analysed. LGA was defined as >2 SD in either birth weight or length for gestational age. The infants were divided into three subgroups: born tall only, born heavy only and born both tall and heavy for gestational age. Multiple logistic and linear regression analyses were performed.

RESULTS

Females, born LGA with regard to length or weight, had a two-fold (adjusted OR 1.96, 95% Cl 1.54-2.48) increased risk to give birth to an LGA infant. Females, born LGA concerning weight only, had a 2.6 (adjusted OR 2.63, 95%, 1.85-3.75) fold increased risk of having an LGA offspring heavy only and no elevated risk of giving birth to an offspring that was tall only, compared to females born not LGA. In addition, maternal obesity was associated with a 2.5 (adjusted OR 2.56, 95%, 2.20-2.98) fold increased risk of having an LGA newborn, compared to mothers with normal weight.

CONCLUSION

Females, born LGA, have an increased risk to give birth to LGA infants, compared to mothers born not LGA. Maternal overweight increases this risk even further.

Maternal upward socioeconomic mobility and black-white disparities in infant birthweight

OBJECTIVES

We estimate the extent to which upward socioeconomic mobility limits the probability that Black and White women who spent their childhoods in or near poverty will give birth to a low-birthweight baby.

METHODS

Data from the National Longitudinal Survey of Youth 1979 and the 1970 US Census were used to complete a series of logistic regression models. We restricted multivariate analyses to female survey respondents who, at 14 years of age, were living in households in which the income-to-needs ratio did not exceed 200% of poverty.

RESULTS

For White women, the probability of giving birth to a low-birthweight baby decreases by 48% for every 1 unit increase in the natural logarithm of adult family income, once the effects of all other covariates are taken into account. For Black women, the relation between adult family income and the probability of low birthweight is also negative; however, this association fails to reach statistical significance.

CONCLUSIONS

Upward socioeconomic mobility contributes to improved birth outcomes among infants born to White women who were poor as children, but the same does not hold true for their Black counterparts.

Evidence of genetic regulation of fetal longitudinal growth

BACKGROUND

Genetic as well as environmental factors are important determinants of fetal growth but there have been few studies of the influence of paternal factors on fetal growth.

AIM

To study the influence of paternal anthropometry on detailed measurements of offspring at birth.

DESIGN

A prospective cohort study involving biochemistry, and anthropometry, of mothers and fathers at 28 weeks gestation, and detailed anthropometry of children within 24 h of birth.

SUBJECTS

567 White Caucasian singleton, non-diabetic, full term pregnancies recruited from central Exeter, UK.

RESULTS

Paternal height, but not paternal BMI, was correlated with birth weight (r = 0.19) and with birth length (r = 0.33). This was independent of potential confounders and maternal height. All measurements of fetal skeletal growth including crown-rump, knee-heel and head circumference were associated with paternal height. Maternal height showed similar correlations with birth weight (r = 0.18) and birth length (r = 0.26). Maternal BMI was correlated with birth weight (r = 0.27) and birth length (r = 0.15). In a multifactorial analysis 38% of the variance in fetal height could be explained by gestation, sex, paternal height, maternal height, maternal glucose, maternal BMI, parity and maternal smoking.

CONCLUSION

Paternal height has an independent influence on size at birth. This predominantly influences length and skeletal growth of the baby. In contrast to maternal obesity the degree of paternal obesity does not influence birth weight. This work suggests that there is genetic regulation of skeletal growth while the maternal environment predominantly alters the adiposity of the fetus.

Sibling birthweight as a predictor of macrosomia in women with type 1 diabetes

AIMS/HYPOTHESIS

The aim of this study was to establish the value of maternal HbA1c levels and older sibling birthweight as predictors of birthweight and macrosomia in the offspring of women with type 1 diabetes.

SUBJECTS AND METHODS

A total of 214 pregnancies of 107 women with type 1 diabetes were studied. Regression analysis was performed to test the predictive value of the birthweight of the first-born infant, HbA(1)c levels, maternal BMI, maternal age and time between subsequent births on the birthweight of the second-born infant. Birthweights were corrected for sex and gestational age. The percentages of first- and second-born infants with macrosomia (weight >90th centile) were calculated and compared.

RESULTS

Only the birthweight of earlier born infants was significantly related to that of second-born infants (p<0.001) and 40-50% of the variation in the birthweight of second-born infants could be explained by the birthweight of the first-born infants. About 85% of the mothers who gave birth to a macrosomic infant had a macrosomic infant in a subsequent pregnancy.

CONCLUSIONS/INTERPRETATION

Although it is clear that glycaemic control contributes to birthweight in women with type 1 diabetes, the birthweight of an earlier born infant appears to be a much better predictor of the birthweight of a subsequent infant than HbA1c levels during pregnancy. It may, therefore, be used to identify patients at risk of giving birth to a macrosomic infant. Daily home monitoring of glucose levels, rather than HbA1c levels, should be used for assessment of maternal glycaemia during pregnancy.

Significant paternal contribution to the risk of small for gestational age

OBJECTIVE

The aim of this study is to investigate both maternal and paternal contributions in the familial aggregation of small for gestational age.

DESIGN

Nested case-control study.

SETTING

Metropolitan area of Haguenau, France.

POPULATION

Data were drawn from a French population-based maternity registry. After selection, 256 cases born either small for gestational age or average for gestational age were included.

METHODS

Controlling for known pregnancy-related risk factors, logistic regression models were used to determine the risk of the child being small for gestational age, given that the mother, father or both were small for gestational age, and to examine interactions between maternal small for gestational age and pregnancy risk factors.

MAIN OUTCOME MEASURES

Specifically, we investigate to what extent having either or both parents born small for gestational age increases the risk of small for gestational age in their offspring, after controlling for the established risk factors of small for gestational age and maternal and paternal characteristics. We also explore the extent to which the intergenerational predictors of small for gestational age may modify the effect of current pregnancy-related risk factors.

RESULTS

The risk of a small for gestational age offspring was 4.7 times greater for mothers and 3.5 times greater for fathers who were small for gestational age, compared with average for gestational age counterparts. Furthermore, the risk of a small for gestational age offspring was 16.3 times greater when both parents were small for gestational age. No significant interactions between maternal small for gestational age and maternal smoking, hypertension or parity were observed.

CONCLUSION

These results indicate that small for gestational age in both mother and father significantly influences the risk of their offspring being small for gestational age. While previous research has indicated that the birth outcome of the mother is an important determinant of the birth outcome of her offspring, these data indicate that the birth outcome of the father plays an equally critical role in determining fetal growth, strongly suggesting a genetic component in the familial aggregation of small for gestational age.

Type 2 diabetes in grandparents and birth weight in offspring and grandchildren in the ALSPAC study

OBJECTIVE

To examine the association between a history of type 2 diabetes and birth weight of offspring and grandchildren.

DESIGN

Prospective observational study. Diabetic status, as reported by mothers (F1 generation) was collected on grandparents (F0) of babies (F2) born to mothers (F1) who participated in a study of maternal and child health. Associations between risk of grandparental diabetes and birth weight in mothers (F1) and grandchildren (F2) were analysed using linear and logistic regression.

SETTING

Avon: comprising of the city of Bristol and surrounding areas.

PARTICIPANTS

12 076 singleton babies (F2), their parents (F1) and maternal and paternal grandparents (F0).

RESULTS

Women (F1) who had no parents with type 2 diabetes had lower birth weights than women with one or two diabetic parents, after controlling for the age of both parents. There was a U shaped association between maternal birth weight and grandmaternal diabetes, but no evidence of an association with grandpaternal diabetes. The grandchildren of maternal grandparents with type 2 diabetes were more likely to be in the top tertile of birth weight than grandchildren of non-diabetics. There was evidence for an inverted U shaped association between birth weight of grandchildren and diabetes in paternal grandmothers.

CONCLUSIONS

This is the first study to show intergenerational associations between type 2 diabetes in one generation and birth weight in the subsequent two generations. While the study has limitations mainly because of missing data, the findings nevertheless provide some support for the role of developmental intrauterine effects and genetically determined insulin resistance in impaired insulin mediated growth in the fetus.

Intergenerational effects on size at birth in South India

Several studies have shown that a baby's birthweight correlates with the birthweight and adult size of both its parents, but more strongly with those of its mother, suggesting that both the 'maternal environment' and inherited genes influence size at birth. There are no previous such intergenerational data from India. Holdsworth Memorial Hospital (HMH), Mysore, South India, has preserved birth records containing the birthweight, length and head circumference of all newborns since 1934. We identified 468 mother-offspring and 341 father-offspring pairs born in the hospital. Daughters and sons (born 1990-95) were heavier at birth than their mothers and fathers, respectively, with a mean (SD) increase in birthweight of 121 g (24 g) between the two generations. The birthweight of both parents predicted offspring birthweight equally (mother: regression slope beta = 255 g/kg; father beta = 251 g/kg; P < 0.001 for both). Paternal birth length had a stronger effect than maternal birth length on offspring birth length. The mother's adult body mass index (BMI) had a greater effect than paternal BMI on offspring birthweight (mother: 18 g/kg/m(2); P < 0.001; father: 15 g/kg/m(2); P = 0.04). In a regression model including data for both parents (available for 57 children) this difference was greater (mother: 46 g/kg/m(2); P < 0.001; father: -10 g/kg/m(2); ns). In contrast, paternal height had stronger effects than maternal height on offspring birth length (mother: 0.8 mm/cm; ns; father: 1.5 mm/cm; P < 0.001). In conclusion, size at birth is influenced by a combination of environmental and genetic factors. Both maternal and paternal birthweight correlate with offspring size at birth. Maternal nutritional status (BMI) influences birthweight. Paternal factors appear to contribute to neonatal skeletal size.

Body Mass Index Change Between Pregnancies and Small for Gestational Age Births

OBJECTIVE

To estimate whether maternal weight changes between pregnancies influence the risk for small for gestational age (SGA) births.

METHODS

SGA cases (n = 8,062) below the tenth percentile birth weight for gestational age were selected from liveborn singletons born of Missouri residents during 1989-1997. Normal weight controls (n = 8,062) were selected according to birth year. The risk of SGA from interpregnancy body mass index (BMI) change and other maternal factors was estimated using logistic regression analysis.

RESULTS

An increase in BMI between pregnancies decreased SGA risk (adjusted odds ratio = 0.8; 95% confidence interval 0.7, 1.0). Other risk factors were prior SGA (4.4; 4.0, 4.8), preeclampsia/eclampsia (2.6; 2.1, 3.2), maternal cardiac disease (1.8; 1.1, 2.9), inadequate weight gain (1.9; 1.8, 2.2), and cigarette smoking (1.9; 1.7, 2.3 for 1-9 cigarettes per day; 2.5; 2.2, 2.8 for 10-19/d; and 2.8; 2.5, 3.3 for 20/d or more).

CONCLUSION

Increase in interpregnancy BMI lowers SGA risk, but adequate weight gain during pregnancy is more effective.

Perinatal growth failure: the road to obesity, insulin resistance and cardiovascular disease in adults

A continuum of increasing risk of adulthood diseases, such as cardiovascular disease, type 2 diabetes and hypertension, with decreasing size at birth is now well-reported and a number of different hypotheses have been proposed. Birthweight links with disease risk markers such as insulin resistance are apparent from childhood, particularly when low birthweight is followed by rapid postnatal weight gain and childhood obesity. Such growth patterns follow fetal growth restraint, associated with maternal-uterine factors such as primiparity, smoking, maternal genes or variations in maternal diet. The fetal metabolic and hormonal responses to intrauterine growth restraint and to rapid postnatal growth are likely to be key to the early pathogenesis of adulthood disease. Thrifty fetal genotypes may enhance these adaptations and improve perinatal survival but predispose to adulthood disease. Their historical selection could explain high prevalences of type 2 diabetes in some ethnic groups, and their identification could allow targeting of potential interventions.

New standards for birth weight by gestational age using family data

OBJECTIVE

This study was undertaken to provide new standards for birth weight according to gestational age through the addition of family data on maternal birth weight and birth weights of previous siblings.

STUDY DESIGN

The analyses were based on 1.7 million births in Norway from 1967 through 1998. These population data were arranged into sibships and mother-offspring units through unique personal numbers. We categorized first births by sex and maternal birth weight and second births by sex and birth weight of the older sibling.

RESULTS

Standards for birth weight per gestational age percentiles differed by >1100 g when the birth weight of an older sibling was considered and by almost 700 g when maternal birth weight was considered. The value of these new standards for birth weight according to gestational age was demonstrated through variation in perinatal mortality.

CONCLUSION

Maternal birth weight and birth weights of previous siblings allow improved predictions of birth weight according to gestational age and should be used for classification of small-for-gestational-age births.

Role of intergenerational effects on linear growth

Current knowledge on the role of intergenerational effects on linear growth is reviewed on the basis of a literature search and recent findings from an ongoing study in Guatemala. Fourteen studies were identified, most of which examined the intergenerational relationships in birth weight. Overall, for every 100 g increase in maternal birth weight, her child's birth weight increased by 10-20 g. The study samples were primarily from developed countries, and birth weight data were extracted from hospital records and/or birth registries. Among the few studies that examined associations between the adult heights of parents and their offspring, correlation coefficients of 0.42-0.5 were reported. None of the studies examined intergenerational relationships in birth length or linear growth patterns during early childhood, preadolescence and/or adolescence. Prospectively collected data from long-term studies being carried out in rural Guatemala provide the first evidence of intergenerational relationships in birth size in a developing country setting. Data were available for 215 mother-child pairs. Maternal birth size was a significant predictor (P < 0.05) of child's birth size after adjusting for gestational age and sex of the child and other potential confounders. Child's birth weight increased by 29 g/100 g increase in maternal birth weight which is nearly twice that reported in developed countries. Similarly, child's birth length increased by 0.2 cm for every 1 cm increase in mother's birth length. The effect of maternal birth weight remained significant even after adjusting for maternal adult size. More evidence from developing countries will help explain the underlying mechanisms and identify appropriate interventions to prevent growth retardation.

The intergenerational relationship between mother's birthweight, infant birthweight and infant mortality in black and white mothers

The relationship between the birthweight of white and black mothers and the outcomes of their infants were examined using the 1988 National Maternal and Infant Health Survey. White and black women who were low birthweight themselves were at increased risk of delivering very low birthweight (VLBW), moderately low birthweight (MLBW), extremely preterm and small size for gestational age (SGA) infants. Adjustment for the confounding effects of prepregnant weight and height reduced the risks of all these outcomes slightly, and more substantially reduced the maternal birthweight associated risk of moderately low birthweight among white mothers. There was little effect of maternal birthweight on infant birthweight-specific infant mortality in white mothers; however, black mothers who weighed less than 4 lbs at birth were at significantly increased risk of delivering a normal birthweight infant who subsequently died. Although the risks for the various outcomes associated with low maternal birthweight were not consistently higher in black mothers compared with white mothers, adjustment for prepregnant weight and height had a greater effect in white mothers than in black mothers. We suggest that interventions to reduce the risks for adverse pregnancy outcomes associated with low maternal birthweight should attempt to optimise prepregnant weight and foster child health and growth.

Trends in perinatal death rates in Denmark and Sweden, 1915-1990

Perinatal mortality rate (PMR) is often taken as an indicator of the quality of obstetric care. Its decline started in the early 1940s in Denmark and Sweden, at the same time as in several other European countries, and its development has been strikingly parallel in the two Scandinavian countries. The changes in the mothers' ages and birth order do not coincide with the changes in the PMR. The percentage of children born weighing less than 2500 g has been very stable over time, albeit higher in Denmark. The move towards hospital confinements in obstetric care took place mainly in the 1930s in Sweden, i.e. before the decline started, and in the 1950s and 1960s in Denmark. The factors investigated have contributed very little to explain why the PMR started to decline in the early 1940s. Factors associated with the distribution of perinatal deaths in a population do not seem to be able to explain the changes taking place over time. In the current study it is postulated that factors behind the change in the PMR are improvements in the mothers' health together with the decline in the total period fertility rate from the beginning of this century. With a smaller number of children the risk of infection was reduced and the amount of food available to each child and pregnant woman increased. This better health in early life may be associated with improved reproductive health in the adult years.

Correlations of birth weight and gestational age across generations

Maternal birth weight is known to be a predictor of offspring birth weight. Less is known about the recurrence of gestational age. In order to estimate the recurrence risk of low birth weight and preterm birth across generations in a population-based sample, 11,092 pairs of mother-firstborn offspring were obtained through an internal linkage in the Norwegian Birth Registry based on the years 1967-1969 (mothers) and 1986-1989 (offspring). A low correlation coefficient of 0.086 was found for gestational age across generations, whereas the correlation between maternal and offspring birth weight was 0.242. Mothers with birth weight below 2500 g had a significantly increased risk (odds ratio = 3.03, 95% conf. interval 1.79-5.11) of having a low birth weight child compared with mothers with birth weight above 4 kg. On the other hand, if the mother was born before the 37th completed week of gestation, the risk of having a preterm child was not significantly increased (odds ratio = 1.46, conf. interval 0.96-2.21) compared with mothers who were born at term. Thus, in contrast to birth weight, human variation in gestational age does not appear to be influenced by genetic factors to any large degree.

The contrasting effects of parental birthweight and gestational age on the birthweight of offspring

Investigations on intergenerational effects on birthweight have been carried out using the data of the 1958 British National Birthday Trust Fund cohort and its follow-up to 23 years, the National Child Development Study (NCDS-4), which included information on all births to cohort members by that age. This report is directed particularly at ascertaining the independent effect of parental gestational age on babies' birthweight. The two main findings are a direct association between parental and offspring birthweight (significant for both mothers and fathers after allowing for confounding factors), but an inverse association with parental gestational age (significant only for the mothers). It is postulated that at least part of this effect is mediated through the association between maternal fetal growth rate and their babies' birthweight; the faster the rate the shorter the gestational age for a given birthweight. It was not possible to ascertain what part genetic factors played in this relationship. Larger and more informative intergenerational studies are needed to further knowledge on this question.

The association of maternal low birthweight and infant low birthweight in a racially mixed population

The association between maternal low birthweight (LBW) and infant low birthweight has been explored in previous studies in mainly middle and upper income, Caucasian populations. This study investigated whether the association found in these populations is true in a racially mixed, low socio-economic group. A case-control methodology was used and estimates of association were derived by means of logistic regression analyses. Data were gathered for 167 LBW infant-mother dyads and 338 adequate weight infant-mother controls matched on race and parity. The odds of a LBW infant having a LBW mother were 80% more likely than for adequate weight infants (OR = 1.80, 95% CI 1.14-2.84). This association was stronger for Hispanic women and their infants than for Black or non-Hispanic White women and their infants. Women who were both preterm and LBW had the higher estimate of risk for infant LBW than women who were LBW due to intrauterine growth retardation (IUGR). As found in previous research, the estimate of association between maternal LBW and infant LBW was greater for those infants who were LBW due to IUGR than those who were LBW due to being premature. The question of whether maternal LBW is also associated with increased risk of neonatal mortality and morbidity is as yet left unanswered.

Gestational duration and birthweight in white, black and mixed-race babies

Using the 1983 United States population of single live births, birthweight and gestational duration were compared for babies of these different parental racial groups: both parents White, mother White-father Black, mother Black-father White, both parents Black. The four groups differed significantly with respect to the usual sociodemographic variables. Mean birthweight and mean gestational duration decreased in that order from the White-White reference group, and conversely there were increasing trends for low birthweight and preterm delivery. Adjustment for the usual sociodemographic variables did not alter these trends appreciably. Group differences were more strongly related to the mother's race than to the father's, and the trends were related to the mother's race. Because the father's race was significant, genetic factors are probably of some importance. The evidence from this study, together with the often-demonstrated relationships between low birthweight and preterm delivery with sociodemographic variables, and the short-term downward secular trends in low birthweight, support the concept that non-genetic maternal factors are more important for these abnormal outcomes. But because neither the usually utilised sociodemographic variables nor genetic factors seem to explain much of the group differences, new approaches are necessary to understand why, irrespective of ethnic group, some women are at excess risk for suboptimal birth outcome.

Is preterm delivery genetically determined?

Surprisingly, the genetics of preterm delivery have received very little attention in the literature. Possible explanations are the inability to obtain accurate information on the length of gestation in family studies and the heterogeneous nature of this disorder. In contrast to the many studies which consider the relative contribution of both genetic and environmental variance to the total variance of birthweight, few studies have examined the genetic basis of the duration of gestation in man. It is argued that both genetic and epidemiological approaches are needed to separate the effects of heredity and the environment on the duration of gestation.

A comparison of recurrent and isolated small-for-gestational-age term births

In this study, based on total Western Australian singleton Caucasian births, women who had repeatedly given birth to small-for-gestational-age (SGA) term infants ('repeater' mothers) were compared with multiparous women who had had only one such infant ('non-repeater' mothers). Women with any preterm births were excluded. The study population comprised 678 repeater and 986 non-repeater mothers. Multiple logistic regression analysis indicated that weight loss or static weight in the third trimester of pregnancy, paternal smoking, low maternal birthweight, short maternal height and unknown family disease history were independent risk factors for repeater status compared with non-repeaters. The risk associated with paternal smoking was confined to mothers who were non-smokers themselves. There may have been a direct association between paternal smoking and recurrent fetal growth retardation or paternal smoking may have acted as a 'marker' for certain behavioural, environmental, social and economic factors which were not measured. Neonatal outcome was worse for the SGA infants of non-repeater mothers than for those of repeater mothers, although the latter were significantly more likely to weight less than 2500 grams.

Height and mortality in the counties of England and Wales

Average heights of adults and children in the counties of England and Wales were examined using national samples of people born between 1920 and 1970. Although height increased over this 50-year period the differences between counties persisted. Average height in a county is closely related to its pattern of death rates, which were derived from all deaths during 1968-78. Counties with taller populations have lower mortality from chronic bronchitis, rheumatic heart disease, ischaemic heart disease and stroke, and higher mortality from three hormone-related cancers, of the breast, prostate and ovary. The inverse relation of height with bronchitis and cardiovascular disease is further evidence of risk factors acting in early childhood. The positive relation between height and cancers of the breast, ovary and prostate could suggest that promotion of child growth has disadvantages as well as benefits.

Growth in utero, blood pressure in childhood and adult life, and mortality from cardiovascular disease

In national samples of 9921 10 year olds and 3259 adults in Britain systolic blood pressure was inversely related to birth weight. The association was independent of gestational age and may therefore be attributed to reduced fetal growth. This suggests that the intrauterine environment influences blood pressure during adult life. It is further evidence that the geographical differences in average blood pressure and mortality from cardiovascular disease in Britain partly reflect past differences in the intrauterine environment. Within England and Wales 10 year olds living in areas with high cardiovascular mortality were shorter and had higher resting pulse rates than those living in other areas. Their mothers were also shorter and had higher diastolic blood pressures. This suggests that there are persisting geographical differences in the childhood environment that predispose to differences in cardiovascular mortality.

Constrained and unconstrained fetal growth: associations with some biological and pathological factors

Data are presented on the birthweights of 1092 siblings and 5207 maternal and paternal relatives of 986 probands. Previous analyses had demonstrated the potency of a maternal regulator constraining fetal growth. Different patterns of birthweights were found in families ascertained, respectively, through very large and very small babies (Ounsted, Scott and Ounsted 1986). When the data were reanalyzed in respect of other biological and pathological factors affecting fetal growth rate the following findings emerged: (1) When pathological factors were associated with the proband pregnancy the typical patterns of pedigree birthweights were not so clearly manifest; (2) general associations were found between the mothers' own birthweights and their size as adults; (3) low maternal birthweight was the biological factor showing the highest risk associated with small babies. When the babies were large the risks associated with high maternal adult weight and parity were similar to those associated with high birthweight. Paternal factors also made a contribution to fast fetal growth rate when pathological factors were absent. These findings confirm our hypothesis that at the lower extreme of fetal growth rate maternal constraint is pre-potent. At the upper extreme, relaxation of constraint allows other biological factors to take up more of the variance.