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

The Maternal Nutritional Buffering Model: an evolutionary framework for pregnancy nutritional intervention

Evidence that fetal nutrition influences adult health has heightened interest in nutritional interventions targeting pregnancy. However, as is true for other placental mammals, human females have evolved mechanisms that help buffer the fetus against short-term fluctuations in maternal diet and energy status. In this review, we first discuss the evolution of increasingly elaborate vertebrate strategies of buffering offspring from environmental fluctuations during development, including the important innovation of the eutherian placenta. We then present the Maternal Nutritional Buffering Model, which argues that, in contrast to many micronutrients that must be derived from dietary sources, the effects of short-term changes in maternal macronutrient intake during pregnancy, whether due to a deficit or supplementation, will be minimized by internal buffering mechanisms that work to ensure a stable supply of essential resources. In contrast to the minimal effects of brief macronutrient supplementation, there is growing evidence that sustained improvements in early life and adult pre-pregnancy nutrition could improve birth outcomes in offspring. Building on these and other observations, we propose that strategies to improve fetal macronutrient delivery will be most effective if they modify the pregnancy metabolism of mothers by targeting nutrition prior to conception and even during early development, as a complement to the conventional focus on bolstering macronutrient intake during pregnancy itself. Our model leads to the prediction that birth weight will be more strongly influenced by the mother’s chronic pre-pregnancy nutrition than by pregnancy diet, and highlights the need for policy solutions aimed at optimizing future, intergenerational health outcomes.

Lay summary: We propose that strategies to improve fetal macronutrient delivery will be most effective if they modify the pregnancy metabolism of mothers by targeting nutrition prior to conception and even during early development, as a complement to the conventional focus on bolstering macronutrient intake during pregnancy itself.

Transgenerational programming of nephron deficits and hypertension

Exposure to a sub-optimal environment in the womb can result in poor fetal growth and impair the normal development of organs. The kidney, specifically the process of nephrogenesis, has been shown to be impacted by many common pregnancy exposures including an inadequate diet, poor placental function, maternal stress as well as maternal smoking and alcohol consumption. This can result in offspring being born with a reduced nephron endowment, which places these individuals at increased risk of hypertension and chronic kidney disease (CKD). Of recent interest is whether this disease risk can be passed on to subsequent generations and, if so, what are the mechanisms and pathways involved. In this review, we highlight the growing body of evidence that a low birth weight and hypertension, which are both major risk factors for cardiovascular and CKD, can be transmitted across generations. However, as yet there is little data as to whether a low nephron endowment contributes to this disease transmission. The emerging data suggests transmission can occur both through both the maternal and paternal lines, which likely involves epigenetic mechanisms such chromatin remodelling (DNA methylation and histone modification) and non-coding RNA modifications. In addition, females who were born small and/or have a low nephron endowment are at an increased risk for pregnancy complications, which can influence the growth and development of the next generation. Future animal studies in this area should include examining nephron endowment across multiple generations and determining adult renal function. Clinically, long term follow-up studies of large birth cohorts need to be undertaken to more clearly determine the impact a sub-optimal environment in one generation has on the health outcomes in the second, and subsequent, generation.

The transgenerational effect of maternal and paternal F1 low birth weight on bone health of second and third generation offspring

Low birth weight programs diseases in adulthood, including adverse bone health. These diseases can have intergenerational and transgenerational origins, whereby transmission to subsequent generations occurs via both parental lines. Uteroplacental insufficiency surgery (Restricted) or sham surgery (Control) was performed on gestational day 18, in F0 Wistar-Kyoto rats. F1 Restricted males and females mated with breeders in order to generate F2 offspring of maternal and paternal lineages. F2 males and females were randomly selected for breeding to generate F3 offspring. F2 and F3 offspring did not have differences in birth weight irrespective of F1 low birth weight and parental line. Maternal line females had minor alterations to trabecular content and density at 6 months, these differences were not sustained at 12 months. Maternal line males had changes to trabecular content at 6 and 12 months; however, differences were no longer present at 16 months. Despite altered bone geometry at 12 and 16 months, bending strength remained unaffected at both ages. Bone health of paternal line females was not affected at 6 and 12 months. Paternal line males at 6 months had changes to trabecular and cortical content; cortical thickness, periosteal circumference and bending strength; however, these differences were no longer sustained at 12 and 16 months. Our data demonstrate that there is no transgenerational transmission of adverse bone health in F2 and F3 offspring, derived from low F1 birth weight females and males. Our results are novel, as bone health across generations and both parental lines has not been investigated in a model of low birth weight due to uteroplacental insufficiency.

Sex-specific associations of maternal birthweight with offspring birthweight in the Omega study

PURPOSE

We investigated nonlinear and offspring sex-specific associations of maternal birthweight (BW) with offspring BW among participants of the Omega study, a pregnancy cohort.

METHODS

Maternal BW was modeled as a continuous variable, linear spline and binary variable indicating low birthweight (LBW; <2500 vs. ≥2500 grams). Offspring BW was modeled as a continuous and binary variable in regression models. Nonlinearity was assessed using likelihood ratio tests (LRTs) in marginal linear spline models.

RESULTS

For every 100-gram increase of maternal BW, offspring BW increased by 22.29 (95% CI: 17.57, 27.02) or 23.41 (95% CI: 6.87, 39.96) grams among mothers with normal BW or born macrosomic, respectively, but not among LBW mothers (β = -8.61 grams; 95% CI: -22.88, 5.65; LRT P-value = .0005). For every 100-gram increase in maternal BW, BW of male offspring increased 23.47 (95% CI: 16.75, 30.19) or 25.21 (95% CI: 4.35, 46.07) grams among mothers with normal BW or born macrosomic, respectively, whereas it decreased 31.39 grams (95% CI: -51.63, -11.15) among LBW mothers (LRT P-value < .0001). Corresponding increases in BW of female offspring (16-22 grams) did not differ among mothers with LBW, normal BW or macrosomia (LRT P-value = .9163).

CONCLUSIONS

Maternal and offspring BW associations are evident among normal BW and macrosomic mothers. These associations differ by offspring sex.

Intergenerational health consequences of the 1959-1961 Great Famine on children in rural China

Using a difference-in-difference method and data from the China Health and Nutrition Survey (CHNS), this paper attempts to quantify the intergenerational health effects on children in rural China of the 1959-1961 Great Famine. By differentiating mother, father, both parents, and none of parents exposed to famine, the analysis puts mother's and father's famine exposure in one unifying framework. Therefore, the methodology achieves identification without concern for multicollinearity and omitted variable bias found in the previous literature. The results imply that children with both parents born in the Great Famine are significantly shorter by 0.37 standard deviations (1.89 cm for boys and 1.78 cm for girls) compared to children with no parents born in the mass starvation. There are also gender and age differences relative to the intergenerational effects of the famine. Girls suffer more than boys, and children between 8 and 12 years of age suffer more than the other age groups.

The intergenerational effects on birth weight and its relations to maternal conditions, São Paulo, Brazil

Background and Objectives. Parents' birth weight acts as a predictor for the descendant birth weight, with the correlation more strongly transmitted through maternal line. The present research aims to study the correlation between the child's low or increased birth weight, the mother's birth weight, and maternal conditions. Methods. 773 mother-infant binomials were identified with information on both the baby's and the mother's birth weight recorded. Group studies were constituted, dividing the sample according to birth weight (<2,500 grams (g) and ≥3,500 grams (g)). The length at birth was also studied in children ≤47.5 cm (lower quartile). Chi² test or Fisher's exact test, Spearman's Rho, and odds ratio were performed in order to investigate the relation between the children's weight and length at birth and the mothers' and children's variables. Results. The girls were heavier at birth than their mothers, with an average increase at birth weight between the generations of 79 g. The child's birth weight <2,500 g did not show any correlation with maternal birth weight <2,500 g (Fisher 0.264; Spearman's Rho 0.048; OR 2.1 and OR lower 0.7) or with maternal stature below the lower quartile (<157 cm) (Chi² sig 0.323; with Spearman's Rho 0.036; OR 1.5 and OR lower 0.7). The child's low birth weight (<2,500 g) was lightly correlated with drug use by the mother during pregnancy (Fisher 0.083; Spearman's Rho 0.080; OR 4.9 and OR lower 1.0). The child's birth weight <2,500 g showed increased correlation with gestational age lower than 38 weeks and 3 days (Chi² sig 0.002; Spearman's Rho 0.113; OR 3.2 and OR lower 1.5). The child's weight at birth ≥3,500 g showed strong correlation with maternal weight at birth ≥3,500 g (Chi² sig 0; Spearman's Rho +0.142; OR 0.5 and OR upper 0.7). It was also revealed that the higher the maternal prepregnancy BMI, the stronger the correlation with child's birth weight ≥3,500 g ((maternal prepregnancy BMI > 25.0 with Chi² sig 0.013; Spearman's Rho 0.09; OR 1.54 and OR upper 2.17) and (maternal prepregnancy BMI > 30.0 with Chi² sig 0 Spearman's Rho 0.137; OR 2.58 and OR upper 4.26)). The child's length at birth in the lower quartile (≤47.5 cm) showed strong correlation with drug use by the mother during pregnancy (Chi² sig 0.004; Spearman's Rho 0.105; OR 4.3 and OR lower 1.5). Conclusions. The mother's increased weight at birth and the prenatal overweight or obesity were correlated with increased weight and length at birth of the newborn, coupled with the tendency of increasing birth weight between generations of mothers and daughters. Also, descendants with smaller length at birth are the children of women with the lowest statures.

Developing a maternally linked birth dataset to study the generational recurrence of low birthweight in Virginia

This paper examined the generational recurrence of low birthweight (LBW) among first-born singletons using a statewide maternally-linked birth dataset. An intergenerational dataset was created by linking 2005-2009 to 1960-1997 Virginia resident live birth data. Maternal information from the recent birth cohort was linked to infant information in the historic birth file using various combinations of mother's name and birthdate. The linked dataset contained 170,624 records (87 % of all eligible records). The analysis dataset was limited to non-Hispanic black and non-Hispanic white first-born singleton infants linked to their mother's own birth record (n = 69,702). Maternal birthweight was a significant predictor of LBW for first-born singletons. The birthweight distribution for both non-Hispanic black and non-Hispanic white infants was shifted toward lower birthweights for infants whose mothers were born LBW. Even after adjusting for known maternal risk factors in the current pregnancy, non-Hispanic black (AOR = 1.6 [95 % CI 1.4, 1.8]) and non-Hispanic white (AOR = 2.0 [95 % CI 1.8, 2.3]) infants had increased odds of being born LBW if their mother was born LBW. A mother's early life experiences can impact the health of her children. These findings underscore the importance of applying a life course perspective to the prevention of LBW. Routine linkage of maternal and infant birth data is needed to strengthen the evidence base for policies and programs that address issues affecting maternal and child health throughout the life course.

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.

Maternal adaptations and inheritance in the transgenerational programming of adult disease

Adverse exposures in utero have long been linked with an increased susceptibility to adult cardio-renal and metabolic diseases. Clear gender differences exist, whereby growth-restricted females, although exhibiting some phenotypic modifications, are often protected from overt disease outcomes. One of the greatest physiological challenges facing the female gender, however, is that of pregnancy; yet little research has focused on the outcomes associated with this, as a potential 'second-hit' for those who were small at birth. We review the limited evidence suggesting that pregnancy may unmask cardio-renal and metabolic disease states and the consequences for long-term maternal health in females who were born small. Additionally, a growing area of research in this programming field is in the transgenerational transmission of low birth weight and disease susceptibility. Pathways for transmission might include an abnormal adaptation to pregnancy by the growth-restricted mother and/or inheritance via the parental germline. Strategies to optimise the pregnancy environment and/or prevent the consequences of inheritance of programmed deficits and dysfunction are of critical importance for future generations.

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.

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.

Paternal and maternal birthweights and the risk of infant preterm birth

OBJECTIVE

Increasing paternal birthweight has been associated with increased risk of fathering a preterm infant, causing speculation that a fetus programmed to grow rapidly can trigger preterm labor.

STUDY DESIGN

Pregnancies occurring from 1974-1989 among women themselves born in the Danish Perinatal Study (1959-1961) were identified through the Population Register; obstetric records were abstracted. Paternal birthweight was obtained by linking Personal Identification Numbers of the fathers to archived midwifery records.

RESULTS

Paternal birthweight was not associated with preterm infants overall. However, there was a significant interaction between paternal and maternal birthweights (P = .003). When the mother weighed less than 3 kg at birth, increasing paternal birthweight was associated with increased occurrence of preterm birth (P for trend = .02); paternal birthweight was unassociated with preterm birth for mothers weighing 3 kg or more at birth (P = .34).

CONCLUSION

When the mother was born small, increasing paternal birthweight was associated with increased risk of preterm birth, suggesting that a fetus growing faster than its mother can accommodate might trigger preterm birth.

Maternal birthweight and outcome of twin pregnancy

There is evidence from singletons that maternal birthweight is positively related to offspring gestational length and birthweight, and some evidence of an inverse relationship with preterm birth. Among twins very preterm birth is the major cause of neonatal mortality and of immediate and later morbidity, including neurodevelopmental impairment. We hypothesised that the relationship between maternal birthweight and gestational length would be more evident in twin than in singleton pregnancies, as there is more variation in gestation in the former. Among 131 singleton mothers carrying twins, there was weak evidence of a positive relationship between maternal birthweight and twin gestational length (+0.6 weeks [95% CI -0.05, +1.3] per kg increase in maternal birthweight, but stronger evidence among 56 of these who went into labour spontaneously (+1.9 weeks [+0.7, +3.1], P = 0.003 for interaction). In the latter group we estimated that the odds of very preterm birth (at <32 weeks) were reduced by 50% [95% CI 10%, 82%] per 250 g increase in maternal birthweight. In the whole cohort, and in this subgroup, maternal birthweight was strongly positively related to both twin offspring total birthweight and total placental weight. Our data, consistent with intergenerational programming of early development, suggest the possibility of a stronger and more clinically relevant association among twins than among singletons. Nevertheless, our sample size was modest and this finding needs to be confirmed in a larger cohort.

Developmental origins of life history: Growth, productivity, and reproduction

There is now much evidence that early life undernutrition elevates risk of diseases like cardiovascular disease. Less clear is whether the underlying developmental plasticity in metabolism and physiology evolved to serve an adaptive function, beyond these effects on pathophysiology. This review builds from principles of life history theory to propose a functional model linking early environments with adult biology. An organism has metabolic potential in excess of survival requirements, called productivity, that supports growth before being shunted into reproduction after growth ceases. This concept from inter-specific studies leads to the prediction that plasticity in growth rate will be positively correlated with components of future adult reproductive expenditure. Consistent with this idea, evidence is reviewed that early nutrition or growth rate predict offspring size in females, and increased somatic investment related to reproductive strategy in males. Thus, population birth weight and sexual size dimorphism are predicted to increase in response to improvements in early nutrition. A striking feature of the continuity of metabolic production is its perpetuation not merely during the lifecycle but across generations: in females, growth rate predicts future nutritional investment in reproduction, which in turn determines fetal growth rate in the next generation. Growth and reproduction serve as mutually-defining templates, thus creating a phenotypic bridge allowing ecologic information to be maintained during ontogeny and transmitted to offspring. Resetting of metabolic production in response to maternal nutritional cues may serve a broader goal of integrating nutritional information within the matriline, thus providing a more reliable basis for adjusting long-term strategy.

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.

Intergenerational effects of preterm birth and reduced intrauterine growth: a population-based study of Swedish mother-offspring pairs

OBJECTIVE

To estimate the intergenerational effects of preterm birth and reduced intrauterine growth.

DESIGN

Population-based cohort study.

SETTINGS

Mother-first-born offspring pairs recorded in the Swedish Medical Birth Registry.

POPULATION

Children born before 2001 to 38 720 women born in 1973-75.

METHODS

The relationships between the mother's and the child's birth characteristics were estimated using logistic regression analysis. Adjustments were made for smoking habits, body mass index (BMI), and current and childhood socio-economic conditions. Analyses were performed on all mother-offspring pairs and on the pairs for which information on neither of the included background variables was missing (n= 24 520).

MAIN OUTCOME MEASURES

Preterm birth (<37 weeks of gestation) and small for gestational age (SGA) (<-2 SD of the Swedish standard).

RESULTS

Mothers who themselves had been born preterm were not significantly more likely to deliver their own children preterm, compared with those who had been born at term (adjusted OR 1.24, 95% CI 0.95-1.62). Also, preterm birth in the mothers did not influence the occurrence of SGA in the children. However, the odds ratio for giving birth to SGA and preterm children, respectively, was higher among SGA mothers (OR 2.68, 95% CI 2.11-3.41 and OR 1.30, 95% CI 1.05-1.61). Mothers whose intrauterine growth was moderately reduced but who did not meet the criterion of being born SGA were also at higher risk of giving birth to both preterm and SGA children, respectively.

CONCLUSIONS

The present study showed evidence of intergenerational effects of reduced intrauterine growth even when socio-economic factors as well as BMI and smoking were adjusted for. There was, however, no consistent intergenerational effect of preterm birth.

The evidence linking maternal nutrition and prematurity

Maternal nutrition may be one of the most important under-evaluated factors contributing to the contemporary rise in prematurity in the United States and other industrialized nations around the world. Slowed fetal growth has been repeatedly shown to be associated with preterm birth, in both singleton and twin pregnancies. Antecedents of impaired fetal growth include a wide variety of factors, including intergenerational effects, biological and social factors related to race and ethnicity, maternal pregravid weight and gestational weight gain, and iron and mineral status. An assessment of maternal nutritional status, including anthropometric factors, is an integral component of effective prenatal care, and may facilitate a reduction in prematurity.

Fetal origins of developmental plasticity: are fetal cues reliable predictors of future nutritional environments?

Evidence that fetal nutrition triggers permanent adjustments in a wide range of systems and health outcomes is stimulating interest in the evolutionary significance of these responses. This review evaluates the postnatal adaptive significance of fetal developmental plasticity from the perspective of life history theory and evolutionary models of energy partitioning. Birthweight is positively related to multiple metabolically costly postnatal functions, suggesting that the fetus has the capacity to distribute the burden of energy insufficiency when faced with a nutritionally challenging environment. Lowering total requirements may reduce the risk of negative energy balance, which disproportionately impacts functions that are not essential for survival but that are crucial for reproductive success. The long-term benefit of these metabolic adjustments is contingent upon the fetus having access to a cue that is predictive of its future nutritional environment, a problem complicated in a long-lived species by short-term ecologic fluctuations like seasonality. Evidence is reviewed suggesting that the flow of nutrients reaching the fetus provides an integrated signal of nutrition as experienced by recent matrilineal ancestors, which effectively limits the responsiveness to short-term ecologic fluctuations during any given pregnancy. This capacity for fetal nutrition to minimize the growth response to transient ecologic fluctuations is defined here as intergenerational "phenotypic inertia," and is hypothesized to allow the fetus to cut through the "noise" of seasonal or other stochastic influences to read the "signal" of longer-term ecologic trends. As a mode of adaptation, phenotypic inertia may help the organism cope with ecologic trends too gradual to be tracked by conventional developmental plasticity, but too rapid to be tracked by natural selection. From an applied perspective, if a trait like fetal growth is designed to minimize the effects of short-term fluctuations by integrating information across generations, public health interventions may be most effective if focused not on the individual but on the matriline.

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.

Integrated perinatal health framework. A multiple determinants model with a life span approach

BACKGROUND

Despite great strides in improving prenatal care utilization among American women, key perinatal indicators have remained stagnant or worsened in the past decade, and the United States continues to rank near the bottom compared to other developed countries. A new approach is needed if we are to achieve improvements in perinatal health.

METHODS

To propose a new framework that integrates a "life span" approach with a multiple determinants model.

RESULTS

We recognize that (1) powerful influences on outcome occur long before pregnancy begins; (2) pregnancy outcome is shaped by social, psychological, behavioral, environmental, and biological forces; and (3) the demography of pregnancy has changed dramatically in the last few decades with more women delaying their first birth. Approaches that simultaneously consider the entire life span as well as multiple determinants may need to be adopted. We propose a framework that integrates these approaches and is supported by the research literature. The life span perspective focuses attention toward the preconceptional and interconceptional periods as targets for intervention in improving perinatal health. The multiple determinants model distinguishes among concepts of disease, health and functioning, and well-being for both women and their offspring.

CONCLUSIONS

Our intent is to influence how policymakers, public health professionals, clinicians, and researchers approach perinatal health.

The malnourished baby and infant

The growth of a baby is constrained by the nutrients and oxygen it receives from the mother. A mother's ability to nourish her baby is established during her own fetal life and by her nutritional experiences in childhood and adolescence, which determine her body size, composition and metabolism. Mother's diet in pregnancy has little effect on the baby's size at birth, but nevertheless programmes the baby. The fetus adapts to undernutrition by changing its metabolism, altering its production of hormones and the sensitivity of tissues to them, redistributing its blood flow, and slowing its growth rate. In some circumstances, the placenta may enlarge. Adaptations to undernutrition that occur during development permanently alter the structure and function of the body.

Growth in utero and blood pressure levels in the next generation

OBJECTIVE

To determine whether blood pressure levels in adult life are related to the mother's fetal growth and size at birth.

DESIGN

A follow-up study of men and women whose mothers' or fathers' size at birth was recorded in Preston, Lancashire, UK.

SUBJECTS

Two hundred and twenty-eight men and women born in Preston, Lancashire, UK, and still living in Lancashire.

MAIN OUTCOME MEASURES

Blood pressure at 18-40 years of age.

RESULTS

Systolic and diastolic pressures fell with increasing mother's birthweight and head circumference. Systolic pressure fell by 2.4 mmHg (95% confidence interval (CI) 0.1-4.7) for each pound increase in mother's birthweight and by 4.0 mmHg (95% CI 0.2-7.8) for each one inch increase in head circumference. These associations were little changed by adjusting for length of gestation or for the subject's age, sex, body mass index or alcohol consumption. They were independent of the mother's blood pressure. As expected, mothers' birthweights were strongly related to their children's birthweights (P= 0.009), but the association between mother's birthweight and offspring's blood pressure was largely independent of this. Father's size at birth was not related to the offspring's blood pressure.

CONCLUSIONS

If the growth of a female fetus is constrained by lack of nutrients, there are persisting changes in her physiology and metabolism which lead to reduced fetal growth and raised blood pressure in the next generation. Public health policies to improve fetal growth in one generation may therefore benefit succeeding generations as well.

Genetic influence on birthweight and gestational length determined by studies in offspring of twins

OBJECTIVE

To determine the relative importance of genetic effects on birthweight, gestational length and small for gestational age.

DESIGN

A cohort study, using individual record linkage between the population-based Swedish Twin and Birth Registers to estimate twin similarities in twins with known zygosity.

POPULATION

Included were 868 monozygotic and 1141 dizygotic female twin pairs, born in Sweden before 1959, who both delivered single births from 1973-1993.

METHODS

Quantitative genetic methods, offspring birthweight, gestational length and small for gestational age birth in twin sisters.

MAIN OUTCOME MEASURES

Twin similarities measured as probandwise concordance rates and intra-class correlations for birthweight, gestational length and small for gestational age births.

RESULTS

Concordance rates and intra-class correlations for birthweight, gestational length and small for gestational age were consistently higher in monozygotic compared with dizygotic twins. Model fitting suggested heritability estimates in the range from 25% to 40%.

CONCLUSIONS

This study suggests genetic effects not only for birthweight and fetal growth, but also for gestational length. The mediation of these genetic effects may partly be due to similarities in maternal antropometric measures, lifestyle and medical complications during pregnancy. The study does not distinguish between fetal and maternal genetic effects.

The Washington State Intergenerational Study of Birth Outcomes: methodology and some comparisons of maternal birthweight and infant birthweight and gestation in four ethnic groups

A statewide database of vital records and hospital discharge summaries of obstetric and neonatal admissions for Washington State in 1987-95 was linked to the birth certificates of mothers born in the state. A total of 46,000 births to mothers of four racial/ethnic groups were studied: Whites, African-Americans, Native Americans and Hispanics. For all four groups inverse associations were found between maternal birthweight and infant low birthweight and preterm birth. The birthweight distribution of African-American mothers was displaced markedly downwards compared with the Whites; this difference in maternal birthweight is offered as a partial explanation of the greater prevalence of suboptimal pregnancy outcomes in the former. In contrast, the maternal birthweight distributions of Whites, Native Americans and Hispanics are similar; differences in pregnancy outcomes are probably more related to maternal preconceptional and postnatal factors in these groups as well as differences in pregnancy-related factors. Mothers' birthweight may have clinical value in identifying high-risk pregnancies.

Preterm and small-for-gestational-age birth across generations

OBJECTIVE

Our purpose was to determine whether women who were themselves small for gestational age at birth are at risk of giving birth to a small-for-gestational-age child and whether women who were themselves preterm at birth are at risk for preterm delivery.

STUDY DESIGN

Women born in Copenhagen as subjects in the Danish Perinatal Study (1959 to 1961) were traced through the Danish Population Register. Information was obtained on their pregnancies during 1974 through 1989.

RESULTS

A total of 25% of the children of small-for-gestational-age women were small for gestational age compared with 11% of the children of non-small-for-gestational-age women. Eleven percent of the children of preterm women were preterm compared with 7% of the children of women born at term. The adjusted odds ratios were 2.0 (95% confidence interval 1.4 to 3.0) for women who were small for gestational age to have small-for-gestational-age children and 1.5 (95% confidence interval 0.9 to 2.5) for women who were born preterm to have preterm children. Small-for-gestational-age women were not at significantly increased risk of preterm delivery (odds ratio 1.2), and preterm women were not at significantly increased risk of having small-for-gestational-age children (odds ratio 1.3).

CONCLUSIONS

Reduced intrauterine growth of the mother is a risk factor for reduced intrauterine growth of her children. However, preterm birth of the mother is not strongly associated with preterm birth of her children.

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.

Similarities and disparities in maternal risk and birth outcomes of white and Japanese-American mothers

This study compares the maternal sociodemographic and prenatal care characteristics and birth outcomes of US resident white and Japanese-American mothers, using data from the state of Hawaii. The specific focus is to determine to what extent these factors can explain variations in newborn maturity and mortality indicators. Single livebirths to resident, non-military dependent white and Japanese-American mothers were selected for analysis from the 1979-1990 linked livebirth-infant death files from Hawaii. Compared with white mothers, Japanese-American mothers were significantly more likely to be married, age 18 years and older, have higher educational attainment, and have adequate prenatal care utilisation. The majority of Japanese-American mothers were born in Hawaii, while the majority of white mothers were born on the US mainland. The mean birthweight of Japanese-American infants was 200 g lighter than that of white infants. Infant mortality rates (IMRs) for both groups were below the US Year 2000 Health Objective. After controlling for maternal sociodemographic and prenatal care factors with logistic regression, Japanese-American infants had significantly higher risks of low birthweight, preterm and very preterm birth and of being small-for-gestational age. These findings indicate that populations with preferential maternal sociodemographic and prenatal care risk indicators may still exhibit higher low birthweight percentages, but achieve comparatively low IMRs.

Timing in prenatal nutrition: a reprise of the Dutch Famine Study

The array of results discussed in this paper is assembled by stage of gestation in the following table (Table 1). We must allow some uncertainty for some outcomes as to the precise stages of gestation in which they originate. For instance, with obesity, the effects of famine exposure may extend beyond the first trimester into the second. Yet, the table is perhaps sufficient in itself to support the point with which the paper opened, namely, that stage of development is crucial to the appreciation of the effects of prenatal nutrition.

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.

Intergenerational studies of human birthweight from the 1958 birth cohort. II. Do parents who were twins have babies as heavy as those born to singletons?

OBJECTIVE

To ascertain whether maternal twinning influences the previously described association between the birthweight of singleton mothers and their infants.

DESIGN AND SUBJECTS

The association between the birthweight of singleton parents and their offspring and that between twin parents and their offspring was compared using data from the 23-year-old sample of the 1958 British national birth cohort. The numbers available for full comparison were 1027 female and 611 male singleton cohort members, and 26 female and 17 male twin cohort members and their first singleton livebirths.

RESULTS

Of the mothers who had been twins, half had been of low birthweight, and overall their mean weight was 700 g less than that of their singleton counterparts. Nevertheless, the mean birthweight of babies of twin mothers was 133 g, and of twin fathers 94 g, greater than of babies of corresponding singletons. For female, but not male, parents this difference persisted after adjustment for confounding variables.

CONCLUSIONS

We suggest two possible reasons for the difference between the weight of babies of twin and singleton mothers. Firstly, the growth of twins becomes retarded late in pregnancy, possibly after a period critical in determining long-term reproductive effects. Secondly, the twin survivors were of higher birthweight than the original twin cohort, whilst the singleton survivors were more representative of all singleton births, thus introducing a possible bias.