Prospective cohort study of factors influencing the relative weights of the placenta and the newborn infant

Effect of maternal asthma on birthweight and neonatal outcome in a British inner-city population

During pregnancy, asthma-related alterations in placental function and the maternal immune system, and reduced growth affecting female but not male fetuses have been reported in a study of selected Australian women. The objective of this study was to evaluate the effect of asthma management, declared during pregnancy, on birthweight and neonatal outcome at an inner-city hospital in England. Between June 2001 and December 2003, women at antenatal clinics were questioned about asthma (n = 10 983). Women with asthma and singleton uncomplicated pregnancies ending at term were selected (n = 718), with non-asthmatic controls (n = 718). Among asthmatic women using inhaled steroids and bronchodilators (n = 170), 43% of the newborn boys had birthweights <10th centile, compared with 27% of controls (P = 0.011; OR 2.51 [95% CI: 1.52, 4.14]). For girls, the proportions were 28% and 27%. In women using bronchodilators only (n = 178) or those declaring no treatment (n = 370), birthweights were not significantly reduced. Taking account of smoking, ethnicity, gestational age and parity, there was a mean birthweight reduction with inhaled steroids and bronchodilators of 118 g [95% CI 36.0, 199.0 g] compared with the control group. There was no interaction between the effect of asthma treatment and infant gender. Infants of asthmatic women in the three subgroups who required intensive care were more likely to exhibit transient tachypnoea of the newborn than infants of control women (P < 0.005). In our population-based sample, the risk of low birthweight among asthmatic women did not depend on infant gender, while neonatal respiratory morbidity remains a significant health issue in boys and girls.

Environmental Programming of Phenotypic Diversity in Female Reproductive Strategies

Among invertebrates, certain hermaphroditic species reproduce sexually, but with no process of sexual differentiation. In such cases the brain is bisexual: Each member of the species develops male and female sexual organs and retains the capacity to express both male and female patterns of reproductive behavior. Members of such species can reproduce socially or alone. Mammals and many other species reproduce both sexually and socially, which requires an active process of sexual differentiation of reproductive organs and brain. The primary theme of this chapter is simply that this process admits to variation and thus individual differences in gender-specific patterns of reproductive function. The focus on this chapter is the often neglected variation in the development of reproductive function in the female mammal. The basic premise is that evolution has not defined any single, optimal reproductive phenotype, but rather encourages plasticity in specific reproductive traits among same sex members of the species that are derived from variations in the quality of the prevailing environment during development that are mediated by alterations in parent-offspring interactions. Thus, the variations in parental care that define the reproductive phenotype of the offspring are influenced by the quality of the environment (i.e., nutrient availability, predation, infection, population density, and so on).

Adiponectin concentration in umbilical cord serum is positively associated with the weight ratio of fetus to placenta

CONTEXT

Adiponectin (APN) concentration in umbilical cord serum is higher than that in adult serum. Except for the positive association between birth weight and cord APN concentration, little is known about the pathophysiological function of APN in fetal development.

OBJECTIVE

The objective of this study was to evaluate the relationship of cord serum APN and IGF-I concentrations with the development of the fetoplacental unit.

DESIGN AND METHODS

Umbilical cord serum APN and IGF-I concentrations were measured in term singleton deliveries (n = 94). The association of cord APN and IGF-I concentrations was evaluated in relation to fetal weight, placental weight, and fetoplacental (F/P) weight ratio.

RESULTS

Mean concentrations and sd of APN and IGF-I were 36.1 +/- 14.0 microg/ml and 58.6 +/- 27.0 ng/ml, respectively. Cord APN concentration was positively associated with F/P weight ratio (r = 0.375, P < 0.001) as well as fetal weight (r = 0.389, P < 0.001) but not placental weight. Cord IGF-I concentration was positively associated with fetal weight (r = 0.405, P < 0.001) and placental weight (r = 0.400, P < 0.001) but not F/P weight ratio. In multiregression analysis, only APN concentration resulted in a significant determinant of F/P weight ratio among variables (beta = 0.376, P < 0.001).

CONCLUSIONS

In cord hyperadiponectinemia, fetuses tend to be disproportionately larger for their placental weight and vice versa in cord hypoadiponectinemia. APN is shown to be the first biomarker positively associated with F/P weight ratio.

Higher maternal dietary protein intake in late pregnancy is associated with a lower infant ponderal index at birth

AIM

A high ponderal index at birth has been associated with later obesity and it has been suggested that intervention to prevent obesity and its sequela should consider the antenatal period. In this context, we investigated the association between maternal nutrition and birth anthropometry.

DESIGN

We analyzed data on 1040 mother-infant pairs collected during the Tasmanian Infant Health Survey (TIHS), Tasmania, 1988-1989. Maternal dietary intake during pregnancy was measured by food frequency questionnaire (FFQ) applied soon after birth. Outcomes of interest were birth weight, birth length, head circumference, ponderal index, head circumference -to-ponderal index ratio, placenta-to-birth weight ratio and head circumference-to-birth length index.

RESULTS

In multiple regression model, an increase of 10 g of absolute protein intake/day was associated with a reduction in birth weight of 17.8 g (95% CI: -32.7, -3.0; P=0.02). Protein intake was also associated negatively with ponderal index (beta=-0.01; 95% CI: -0.02, -0.00; P=0.01). A 1 % increase in carbohydrate intake resulted in a 1% decline in placental weight relative to birth weight. Higher protein intake in the third trimester was associated with a reduced ponderal index among large birth weight infants but not low birth weight infants.

CONCLUSIONS

This raises the possibility that any effect of high protein in altering infant anthropometry at birth may involve changes in body composition and future work to examine how a high-protein diet influences body composition at birth is warranted.

Maternal obesity, metabolism, and pregnancy outcomes

About one third of all pregnant women in the United States are obese. Maternal obesity at conception alters gestational metabolic adjustments and affects placental, embryonic, and fetal growth and development. Neural tube defects and other developmental anomalies are more common in infants born to obese women; these defects have been linked to poor glycemic control. Preeclampsia, a gestational disorder occurring more frequently in obese women, appears to be due to a subclinical inflammatory state that impairs early placentation and development of its blood supply. Fetal growth and development during the last half of pregnancy depends on maternal metabolic adjustments dictated by placental hormones and the subsequent oxygen and nutrient supply. Maternal obesity affects these metabolic adjustments as well. Basal metabolic rates are significantly higher in obese women, and maternal fat gain is lower, possibly in response to altered leptin function. The usual increase in insulin resistance seen in late pregnancy is enhanced in obese mothers, causing marked postprandial increases in glucose, lipids, and amino acids and excessive fetal exposure to fuel sources, which in turn increases fetal size, fat stores, and risk for disease postnatally. Impaired glucose tolerance, gestational diabetes, and hyperlipidemia are more common among obese mothers. To date, little attention has been given to the role of diet among obese women in preventing these problems. However, studies of women with impaired glucose tolerance show that replacing refined carbohydrates and saturated fat with complex, low-glycemic carbohydrates and polyunsaturated fatty acids improves metabolic homeostasis and pregnancy outcomes. Thus, current dietary guidelines regarding the amount and type of carbohydrates and fat for nonpregnant women seem appropriate for pregnant women as well.

Interactions between fetal HLA-DQ alleles and maternal smoking influence birthweight

Maternal smoking during pregnancy inhibits fetal growth, and is a major cause of childhood and adult morbidity, including increased risks of cardiovascular disease and diabetes. However, the use of birthweight as a proxy for future smoking-related morbidity is hindered by its wide variability, suggesting a role for other birthweight-modifying factors. We report here, for the first time, that interactions between specific fetal HLA-DQA1 and DQB1 alleles and maternal smoking can influence birthweight. We compared mean birthweights of a series of term, HLA-DQ typed white UK newborns (n = 552) whose mothers had either smoked (n = 211) or not smoked (n = 341) during pregnancy. Maternal smoking during pregnancy resulted in an average birthweight reduction of 244 g, but the combined effects of maternal smoking and fetal DQA1*0101 or DQB1*0501 alleles resulted in a 230 and 240 g further reduction in mean birthweight, respectively, resulting from interactions between smoking and these DQ types. Other fetal DQ allele-specific interactions with maternal smoking are suggested by a "protective" effect on smoking-associated birthweight reduction in newborns typing for DQA1*0201 and DQB1*0201. Our results suggest biological interactions between maternal cigarette smoking during pregnancy and specific fetal DQ alleles that affect fetal growth. The precise nature of these interactions merits further investigation, as knowledge of fetal HLA-DQ type may be useful in refining risk estimates of severe fetal growth restriction because of maternal smoking during pregnancy.

Fetal haematocrit is a determinant of placental size in term pregnancies

Placental size may be influenced by maternal factors, placental function as well as the fetal condition. So far, no studies have examined how the fetal oxygen-carrying capacity or haemoglobin/haematocrit levels would affect placental growth in normal human pregnancies. The aim of this study was to investigate the relationships between placental size and fetal arterial cord blood haemoglobin and haematocrit levels at the time of caesarean delivery. Umbilical arterial cord blood was taken for arterial haemoglobin and haematocrit levels immediately after delivery. The relative placental size (defined by the ratio of placental weight to fetal weight) was inversely correlated with both arterial haemoglobin (r = -0.455, p = 0.001) and haematocrit levels (r = -0.425, p = 0.003) in women who had undergone elective caesarean sections. No significant correlation was found between the relative placental size with other maternal and fetal factors.

The association between intrauterine growth restriction in the full-term infant and high blood pressure at age 7 years: results from the Collaborative Perinatal Project

OBJECTIVE

To use neonatal and placental anthropometry as proxy measures of intrauterine growth restriction (IUGR) and to relate these to blood pressure later in childhood.

STUDY DESIGN

A post hoc analysis of full-term white and black children from the Collaborative Perinatal Project, followed from birth until age 7 years (n = 29,710). Blood pressure above the 90th percentile by gender and race was considered high blood pressure. Anthropometric measures at birth included birth weight, ponderal index (PI, birth weight/birth length(3)), head to chest circumference (HCC) ratio, and placental ratio percentage (PRP, placental weight(*)100/birth weight).

RESULTS

Among anthropometric measures, PI, HCC, and birth weight were not associated with high systolic blood pressure at age 7 years, but PRP was. In multiple logistic regression, high systolic blood pressure and widened pulse pressure were both predicted by increased PRP [odds ratio (OR) 1.03 and 1.04, P < 0.001] but not by birth weight, when adjusted for gender, race, and maternal education. High diastolic blood pressure was weakly predicted by birth weight (OR 1.10, P = 0.05) but not by PRP.

CONCLUSIONS

PRP is associated with an increased risk for high systolic blood pressure and pulse pressure later in childhood, whereas birth weight, PI, and HCC are not. The proportion of placental weight to birth weight is a useful marker of IUGR for studying the developmental origins of adult disease hypothesis.

Perinatal and childhood origins of cardiovascular disease

BACKGROUND

Features of the metabolic syndrome comprise a major risk for cardiovascular disease and will increase in prevalence with rising childhood obesity. We sought to identify early life influences on development of obesity, hypertension and dyslipidemia in children.

METHODS AND RESULTS

Cluster analysis was used on a subset of a longitudinal Australian birth cohort who had blood samples at age 8 (n=406). A quarter of these 8-year-olds fell into a cluster with higher body mass index, blood pressure (BP), more adverse lipid profile and a trend to higher serum glucose resembling adult metabolic syndrome. There was a U-shaped relationship between percentage of expected birth weight (PEBW) and likelihood of being in the high-risk cluster. The high-risk cluster had elevated BP and weight as early as 1 and 3 years old. Increased likelihood of the high-risk cluster group occurred with greatest weight gain from 1 to 8 years old (odds ratio (OR)=1.4, 95% confidence interval (CI)=1.3-1.5/kg) and if mothers smoked during pregnancy (OR=1.82, CI=1.05-3.2). Risk was lower if children were breast fed for >/=4 months (OR=0.6, 95% CI=0.37-0.97). Newborns in the upper two quintiles for PEBW born to mothers who smoked throughout pregnancy were at greatest risk (OR=14.0, 95% CI=3.8-51.1) compared to the nadir PEBW quintile of non-smokers.

CONCLUSION

A U-shaped relationship between birth weight and several components of the metabolic syndrome was confirmed in a contemporary, well-nourished Western population of full-term newborns, but post-natal weight gain was the dominant factor associated with the high-risk cluster. There was a prominence of higher as well as lowest birth weights in those at risk. Future health programs should focus on both pre- and post-natal factors (reducing excess childhood weight gain and smoking during pregnancy), and possibly the greatest benefits may arise from targeting the heaviest, as well as lightest newborns, especially with a history of maternal smoking during pregnancy.

Normal and abnormal fetal growth

The fetal origins of adult disease hypothesis suggests that poor intrauterine growth is associated with an increased risk of cardiovascular disease. The hypothesis goes on to implicate different growth 'phenotypes', particularly disproportionate growth, in the determination of the type of cardiovascular disease that develops. Analysis of the antenatal growth of a low-risk pregnancy population does not identify such growth phenotypes within the general population. Rather, intrauterine growth is characterized by poor predictability of subsequent size, suggesting that centile crossing is a common feature of intrauterine growth. Furthermore, there is a sexually dimorphic pattern to this growth that needs to be considered in further work to test the fetal origins hypothesis.

Nutritional intake and placental size in gestational diabetic pregnancies--a preliminary observation

A disproportionately large placenta may represent an adaptive response to adverse intrauterine conditions. Both maternal nutritional intake and presence of gestational diabetes (GDM) have been found to affect relative placental growth. As dietary modification is part of the standard management in GDM women, the observed increase in placental size in these women may be partly due to dietary modification. In this study, we set out to examine the relationship between dietary intake and placental size in GDM pregnancies. Food diaries for five consecutive days for 52 women diagnosed with GDM were obtained to assess their nutritional intake in terms of total calories, carbohydrate, protein and fat. Spearman's correlations were calculated for nutritional intake and various factors that may correlate with placental weight. There was a significant inverse relationship (P=0.021) between placental weight and protein intake. No correlations with the other two nutritional components could be demonstrated. Maternal nutritional intake was not correlated with infant birthweight. It is possible that dietary modulations improve GDM pregnancy outcome, not only by improving glycaemic controls but also by affecting placental growth by altering the proportion of protein intake.

Evolutionary perspectives on pregnancy: maternal age at menarche and infant birth weight

We present a novel evolutionary analysis of low birth weight (LBW). LBW is a well-known risk factor for increased infant morbidity and mortality. Its causes, however, remain obscure and there is a vital need for new approaches. Life history theory, the most dynamic branch of evolutionary ecology, provides important insights into the potential role of LBW in human reproductive strategies. Life history theory's primary rationale for LBW is the trade-off between current and future reproduction. This trade-off underlies the prediction that under conditions of environmental risk and uncertainty (experienced subjectively as psychosocial stress) it can be evolutionarily adaptive to reproduce at a young age. One component of early reproduction is early menarche. Early reproduction tends to maximise offspring quantity, but parental investment theory's assumption of a quantity-quality trade-off holds that maximizing offspring quantity reduces quality, of which LBW may be the major component. We therefore predict that women who experienced early psychosocial stress and had early menarche are more likely to produce LBW babies. Furthermore, the extension of parent-offspring conflict theory in utero suggests that the fetus will attempt to resist its mother's efforts to reduce its resources, allocating more of what it does receive to the placenta in order to extract more maternal resources to increase its own quality. We propose that LBW babies born to mothers who experience early psychosocial stress and have early menarche are more likely to have a higher placental/fetal weight ratio. We review evidence in support of these hypotheses and discuss the implications for public health.

Sexual dimorphism in the growth hormone and insulin-like growth factor axis at birth

In rodents and humans there is a sexually dimorphic pattern of GH secretion that influences the serum concentration of IGF-I. Pattern differences can be identified in children, but it is not known how early this difference is established. We studied the plasma concentrations of IGF-I, IGF-II, IGF-binding protein-3 (BP-3), and GH in cord blood taken from the offspring of 1650 singleton Caucasian pregnancies born at term and related these values to birth weight, length, and head circumference. Pregnancies complicated by preterm delivery, antepartum hemorrhage, pregnancy-induced hypertension, preeclampsia, or gestational diabetes and where cigarette smoking continued were excluded, resulting in a cohort of 987. Cord plasma concentrations of IGF-I, IGF-II, and IGFBP-3 were influenced by factors influencing birth size: gestational age at delivery, mode of delivery, maternal height, and parity of the mother. Plasma GH concentrations were inversely related to the plasma concentrations of IGF-I and IGFBP-3; 10.2% of the variability in cord plasma IGF-I concentration and 2.7% for IGFBP-3 was explained by sex of the offspring and parity. None of the factors, apart from maternal height, influenced cord serum IGF-II concentrations (adjusted r(2) = 1%). Sex of the baby, mode of delivery, and parity influenced cord serum GH concentrations (adjusted r(2) = 2.6%). Birth weight, length, and head circumference measurements were greater in males than females (P < 0.001). Mean cord plasma concentrations of IGF-I (males, 66.4 +/- 1.2 micro g/liter; females, 74.5 +/- 1.3 micro g/liter; P < 0.001) and IGFBP-3 (males, 910 +/- 13 micro g/liter; females 978 +/- 13 micro g/liter; P < 0.001) were significantly lower in males than females. Cord plasma GH concentrations were higher in males than females (males, 30.0 +/- 1.2 mU/liter; females, 26.9 +/- 1.1 mU/liter; P = 0.05), but no difference was noted between the sexes for IGF-II (males, 508 +/- 6 micro g/liter; females, 519 +/- 6 micro g/liter; P = NS). After adjustment for gestational age, parity, and maternal height, cord plasma concentrations of IGF-I and IGFBP-3 along with sex explained 38.0% of the variability in birth weight, 25.0% in birth length, and 22.7% in head circumference. These data demonstrate that in a group of singleton Caucasian babies born at term, cord plasma IGF-I, IGFBP-3, and GH concentrations relate to birth size, with evidence for sexual dimorphism in the GH-IGF axis.

Nutrition and the early origins of adult disease

There is now overwhelming evidence that much of our predisposition to adult illness is determined by the time of birth. These diseases appear to result from interactions between our genes, our intrauterine environment and our postnatal lifestyle. Those at greatest risk are individuals in communities making a rapid transition from lives of 'thrift' to a lives of 'plenty'. From a global perspective, such origins of diabetes, coronary heart disease and stroke, should render research in these fields as one of the highest priorities in human health care. Prevention will be enhanced by elucidation of the mechanisms by which the fetus is programmed by the mother for the life she expects it to live. At the present time, there is evidence that fetal nutrition and premature exposure to cortisol are effective intrauterine triggers, but a multitude of alternative pathways require investigation. It is also likely that programming extends across generations, and may involve the embryo and perhaps the oocyte. An oocyte that becomes an adult human develops in the uterus of its grandmother, so further research is required to describe the role of environments of grandmothers and mothers in predisposing offspring to health or illness in adult life.

Placental weight and its ratio to birthweight in a Ukrainian city

BACKGROUND

Placental weight and its ratio to birthweight have recently been reported to predict later chronic disease. These fetal growth indicators have been measured in the west for over a century with consistent results when methods of preparation were comparable. We investigated whether recent difficult conditions in the former eastern bloc have altered placental weight or its relationship to other fetal size measures from what has historically been reported.

METHODS

Placentas were obtained from 1621 singleton births of at least 28 weeks gestation in a Ukrainian city during 1993-1994, using a systematic protocol. Maternal characteristics were obtained from questionnaires. Pregnancy complications and birth size measures (infant weight, length, crown-rump length, and head circumference) were abstracted from medical records. We examined relationships of placental weight and ratio to these variables.

RESULTS

Placental weight ranged from 100 to 1000 g, with a mean of 470 g. Mean placental ratio was 13.9%. Placental weights increased and ratios decreased with gestational age. Larger ratios were related to larger maternal BMI. Absolute measures of infant size and placental weight were mutually positively correlated. Placental ratio, infant length, and ponderal index (PI) were nearly uncorrelated.

CONCLUSIONS

Absolute and relative weights of Ukrainian placentas were similar to historical reports, as were their relationships to other infant size indicators. Placental weight ratio (PWR), ponderal index, and infant length measured different birth size dimensions. Placental availability, consistency of placental measurements, and placental ratio's reflection of an independent facet of fetal growth make the placenta a useful research tool.

Prenatal ultrasound biometry related to subsequent blood pressure in childhood

STUDY OBJECTIVE

To relate measures of fetal growth/size other than birth weight with subsequent blood pressure measured on the same individuals within the context of the "fetal origins of adult disease".

DESIGN

A prospective cohort study in which measurements of fetal dimensions obtained by serial ultrasound imaging between 18 and 38 weeks gestation were analysed with reference to systolic blood pressure measurements on the offspring at age 6 years.

SETTING

Perth, Western Australia.

PARTICIPANTS

A subgroup of 707 eligible mother-fetus pairs from a cohort of 2876 pregnant women and their offspring. The number of mother-fetus pairs varied at each gestational age and by measurement of fetal dimension. Subsequent blood pressure recordings were obtained on approximately 300 of the offspring at age 6 years.

MAIN RESULTS

The findings confirmed the inverse association between birth weight and systolic blood pressure at age 6. There was, also, an inverse relation between fetal femur length and systolic blood pressure at age 6, adjusted for current height. Furthermore, an inverse association was demonstrated between a statistically derived measure of fetal growth (conditional z score) between 18 and 38 weeks gestation and later systolic blood pressure at age 6. The effect sizes for all three relations were in the order of 1-2 mm Hg per standard deviation change.

CONCLUSION

The mechanisms underpinning the "fetal origins" hypothesis may be operative early in pregnancy and may be reflected in the length of the fetal femur in early to mid-pregnancy.

Weight, volume and surface area of placenta of normal pregnant women and their relation to maternal and neonatal parameters in Malay, Chinese and Indian ethnic groups

This study was conducted to determine the effect of ethnicity on maternal, placental and neonatal parameters. Maternal, placental, and the newborn parameters were corrected for gestational age. The male:female sex ratio was 1:1.03. One hundred and forty-four freshly delivered placentae from 55 Malaysian, 51 Chinese, and 38 Indian normal healthy patients were collected and standard stereological methods used to estimate the placental parameters. Pearson's correlation, Spearman's correlation and 1-way ANOVA were used to test significance of differences. Placental surface area, placental weight and placental volume of Indians were lower than Malays (P< 0.05). Placental weight correlated significantly with neonatal length (r=0.527), birthweight (r=0.665), head circumference (r=0.371) and booking weight (r=0.193) while placental volume correlated with neonatal length (r=0.588), birthweight (r=0.688), head circumference (r=0.384), parity (r=0.202) and booking weight (r=0.219) at P< 0.05. Indian babies weight and length were less than Chinese and Malay babies (P< 0.05) while booking weight of Indian mothers was less than those of Chinese mothers (P< 0.05). Even after being corrected for booking weight, placental parameters of Indian patients were still significantly less than Malays and Chinese (P< 0.05).

Intrauterine growth and its relationship to size and shape at birth

Birth size and shape are commonly used as indicators of fetal growth. Epidemiologic studies have suggested a relationship between birth size and the risk of developing cardiovascular disease in later life. Certain "growth phenotypes" have been linked to the development of certain components of cardiovascular disease, particularly babies who display disproportional growth in utero. These observations are based on retrospective analysis of historical data sets. If the "Fetal Origins of Adult Disease" hypothesis is to be generalisable to the present day, then it is essential to establish whether these "growth phenotypes" exist within the normal distribution of birth size. The UCL Fetal Growth Study is a prospective study of antenatal fetal growth assessed by ultrasound at 20 and 30 wk gestation in 1650 low risk, singleton, white pregnancies. Measures of birth size were obtained and analyzed by principal components to explain shape at birth. Birth measures were also related to antenatal growth measurements to determine the strength of ultrasound evaluation in determining subsequent growth. There was significant sexual dimorphism in all measures at birth, with males heavier, longer, and leaner than females. From 20 wk of gestation onwards, males had a significantly larger head size than females. Parity, maternal height, and body mass index were important determinants of birth weight (p < 0.001). Cigarette smoking influenced birth weight, length, and head circumference (p < 0.001) but had no effect on placental size. Principal component analysis revealed that proportionality was the predominant size/shape at birth (55% of variance explained). A further 18% of variance was explained by a contrast between weight, head circumference, and length versus three skinfolds. Anthropometric measures as assessed by ultrasound at 20 and 30 wk gestation were poor predictors of birth length, weight, and head circumference (adjusted R(2) 18, 40, and 28% at 30 wk gestation scan, respectively). These predictions were not improved by including growth patterns between 20 and 30 wk. There is sexual dimorphism in a number of anthropometric measures at birth and in utero. These sex differences are important determinants of body size and shape. In a low risk population delivering at term, body shape was largely determined by proportionality between anthropometric measures. The low correlations between antenatal measures and birth size suggest that it is unwise to ascribe birth shape phenotypes to adverse events at any particular stage of gestation. The weak relationship also suggests that routine antenatal scans around 30 wk of gestation to predict growth problems are unlikely to be of benefit in the majority of cases.

Undernutrition during the first half of gestation increases the predominance of fetal tissue in late-gestation ovine placentomes

OBJECTIVE

To investigate, in sheep, the effects of maternal undernutrition during the first half of pregnancy on placental growth and development and fetal growth.

STUDY DESIGN

Six ewes (R) were subjected to a 15% reduction in nutrient intake for the first 70 days of gestation and thereafter received the recommended daily intake. Another group of six ewes (C) received the recommended daily intake throughout pregnancy. At 130 days gestation the ewes were killed and morphological and morphometrical measurements were carried out on the placenta and fetus.

RESULTS

Undernutrition resulted in a significant alteration in placental morphology, which was seen as increased growth of the fetal side of the placenta in R animals. However, fetal size in late gestation was not affected by the undernutrition, suggesting that placental adaptation was successful in maintaining fetal growth.

CONCLUSION

Placental adaptations, including changes in gross morphology, may preserve fetal growth if maternal undernutrition is not severe. The mechanisms remain to be elucidated.

Placental weight and placental ratio as predictors of later blood pressure in childhood

OBJECTIVE

A significant inverse relationship between blood pressure and birth weight is firmly established. This association may be the result of fetal adaptations to an adverse intrauterine environment. Further markers of intrauterine growth include the weight of the placenta and the placental ratio (the ratio of placental weight to birth weight). A number of studies suggest that a decreased placental weight or an elevated placental ratio may be independent risk factors for subsequent high blood pressure. The overall evidence for this is, however, inconclusive. The purpose of the present study was to clearly define the relationships between placental weight, placental ratio and subsequent blood pressure during childhood.

DESIGN

Prospective cohort study of 2507 singleton children, born at term during 1989-1992. Blood pressures were recorded at ages 1, 3 and 6 years, using a semi-automated oscillometric device.

RESULTS

Inverse relationships existed between both systolic and diastolic blood pressure and placental weight, adjusted for current weight at ages 1, 3 and 6 years. The relationships between placental weight and systolic blood pressure were statistically significant at ages 1 and 3 years. There was no consistent relationship between placental weight and later blood pressure within birth weight categories. No clinically or statistically significant association was seen between the placental ratio and either systolic or diastolic blood pressures at any age.

CONCLUSIONS

Birth weight, rather than placental weight or their ratio, is the early life factor most importantly related to subsequent blood pressure in childhood.

Effect of early maternal iron stores on placental weight and structure

BACKGROUND

Large placental size and low birthweight have been implicated as factors predicting high blood pressure in adulthood. Maternal anaemia has been suggested as a link. We investigated the interaction between maternal iron status and other factors known to influence birthweight and placental size.

METHODS

In a prospective study of 1650 low-risk, singleton, caucasian pregnancies, we related placental size and birthweight to maternal iron status, socioeconomic status, and parity. Placental morphology was assessed in 17 randomly chosen primigravid pregnancies.

FINDINGS

Parity was an important determinant of birthweight (mean standard deviation score -0.13 [SD 0.90] para 0; -0.24 [0.90] para 1; 0.32 [1.1] para 2; 0.21 [1.1] para > or = 3; p<0.0001) and placental weight (mean 655 g [SD 130]; 679 g [122]; 675 g [139]; 694 g [157], respectively; p=0.01). Cigarette smoking influenced birthweight only. Socioeconomic status had little effect after correction for parity. In addition to parity, the factors influencing placental weight were maternal height, weight, and serum ferritin concentration at booking, but not haemoglobin concentration. Serum ferritin concentrations were associated with folate intake and parity. In the placental morphology subset, serum ferritin concentration was inversely related to overall measures of peripheral villous capillarization. Haemoglobin concentration showed no such association.

INTERPRETATION

These findings show a relation between maternal anaemia and placental size and birthweight across the normal range for these measures. Low ferritin concentrations in early pregnancy were associated with increased placental vascularisation at term. The association between ferritin concentration and folate supplementation emphasises the importance of preconceptional health, particularly in women at high risk of iron deficiency.

The neonatal implications of a high placental ratio in small-for-gestational age infants

An increased placental ratio has been associated with small-for-gestational age (SGA) infants. A retrospective study on 252 singleton SGA infants without major anomalies born within a 1-year period was performed to determine the relationship between placental ratio and maternal/infant characteristics, and perinatal complications. The cases were categorized into three groups according to the placental ratio (<1 sd below the mean, within 1 sd of the mean, >1 sd above the mean) based on our previous data. There were more infants with a high ratio (32.9 per cent) than with a low ratio (15.5 per cent). While there was no difference in the maternal characteristics or antenatal complications, there was a significant trend in decreasing birthweight and an increasing placental weight in relation to an increasing placental ratio. The infants with a high ratio had increased incidence of meconium stained liquor, hypocalcaemia, hypomagnesaemia and phototherapy, a trend that was consistent even after exclusion of the preterm infants. Our data indicated that a high placental ratio in SGA infants was due to both increased placental size and decreased birthweight, and this was associated with increased neonatal morbidity.

Adaptive angiogenesis in placentas of heavy smokers

Smoking in pregnancy increases perinatal morbidity and mortality, suggesting impaired placental function, though placental weight is increased. We used scanning electron microscopy to show adaptive angiogenesis in term placental villi from smokers (n=4) and non-smokers (n=4). These images may aid communication of the dangers of smoking in pregnancy.

Maternal, but not fetal, administration of corticosteroids restricts fetal growth

OBJECTIVE

Previous studies have shown that repeated doses of corticosteroids given to pregnant sheep improve postnatal lung function, but restrict fetal growth. Repeated administration of corticosteroids directly to the fetus also enhances postnatal lung function. The purpose of the present study was to investigate and characterize the relative effects on growth of repeated maternal and fetal treatments by study of body, organ, and placental weights.

METHODS

Date-bred pregnant sheep were given intramuscular betamethasone or saline to either the mother or fetus on three occasions at weekly intervals commencing at 104 days gestation, followed by cesarean section at 125 days. Twenty-two animals which had received three doses of betamethasone were compared with 21 which had received a single dose at 104 days and with 12 saline-treated controls.

RESULTS

Repeated maternal doses of betamethasone resulted in reductions in birthweight and weights of the placenta and major organs. Direct fetal injection did not affect birthweight, placental weight, placental/ birthweight ratio, or weights of the major organs with the exception of the liver.

CONCLUSIONS

Administration of repeated doses of betamethasone directly to the sheep fetus does not produce the growth-restricting effects induced by maternal administration and does not affect the placental/birthweight ratio.

Maternal smoking during pregnancy, growth, and bone mass in prepubertal children

There have been no studies of smoking during pregnancy and bone mineralization in children. The objective of this population-based longitudinal study was to determine whether maternal smoking during pregnancy is associated with bone mass and other growth variables in prepubertal children. We studied 330 8-year-old male and female children representing 47% of those who originally took part in a study of risk factors for Sudden Infant Death Syndrome in 1988. The main outcome measures were bone mineral density measured by a Hologic QDR2000 densitometer: birth weight, placental weight, height, and weight. Maternal smoking during pregnancy was associated with deficits in growth with these children having lower height (-1.53 cm, 95% confidence interval [CI] -3.03 to -0.03) and a trend to lower weight (-1.35 kg, 95% CI -2.75 to 0.11) at age 8. Furthermore, there was a disproportionate deficit in bone mass such that those children whose mothers smoked during pregnancy had lower size adjusted bone mass at the lumbar spine (-0.019 g/cm2, 95% CI -0.033 to -0.005) and femoral neck (-0.018 g/cm2, 95%CI -0.034 to -0.002) but not total body (-0.005 g/cm2, 95% CI -0.015 to 0.005). This association was only present for children born at term. Mothers who smoked during pregnancy also had lower placental weight (- 56 g, 95% CI -95 to -17), and further adjustment for placental weight led to nonsignificant results for smoking with both growth and bone parameters, suggesting that these associations may be mediated through placental size and function. Maternal smoking habit in 1996 was not significantly associated with bone mass at any site. In conclusion, this study has demonstrated a long-term negative association between maternal smoking during pregnancy and both growth and bone mass in children born at term, and suggests that the timing of exposure rather than the dose or duration is critical. If these associations are present in other populations and they persist until the attainment of peak bone mass, then our findings suggest that osteoporosis prevention programs should start very early in the life cycle.

Increased fetoplacental angiogenesis during first trimester in anaemic women

BACKGROUND

Epidemiological studies describe an association between relative size of the placenta at delivery and cardiovascular morbidity and mortality during adult life. Some determinants of placental size, such as maternal anaemia, have been acknowledged, but no plausible mechanism has been advanced to explain the initiation of postnatal disease.

METHODS

Placental villous vascularisation in anaemic women (Hb<90 g/L) was assessed in the first and third trimesters of pregnancy by immunohistochemical identification of villous capillaries and compared with that of gestational age-matched groups of women with normal (Hb>110 g/L; control group) concentrations of haemoglobin, and an intermediate group (Hb 90-110 g/L).

FINDINGS

Anaemia, especially in the first trimester, was associated with increased numbers of capillaries per villous cross section (mean 11.70 [SE 0.35] vs 4.14 [0.27]) located mainly in the outer third of the stroma beneath the trophoblast (94% [1.15] vs 67% [1.82]) and with increased numbers of villous macrophages and of proliferating MIB-1-positive cells compared with the control group.

INTERPRETATION

Maternal anaemia in early pregnancy seems to influence the pattern of placental vascularisation. Such changes might alter placental vascular impedance during early fetal life, thereby exerting important effects on cardiovascular development.

Influence of restricted maternal nutrition in early to mid gestation on placental and fetal development at term in sheep

We investigated the influence of restricted maternal nutrition between 28 and 77 d of gestation on placental weight and appearance, and on fetal weight and conformation. Single-bearing ewes were fed either twice [i.e. controls (n = 19)] or half [i.e. nutrient-restricted (n = 28)] their energy requirements from 28 to 77 d of gestation, after which all ewes were fed to fully meet the energy requirements for maintenance and pregnancy. Close to term (145 +/- 1 d) placental weight was higher in the nutrient-restricted group [nutrient-restricted, 416.3 +/- 12.6 g; controls, 347.4 +/- 17.6 g (p < 0.01)], as was the abundance of everted placentomes. There was no significant difference in total fetal weight, or weights of individual organs between groups, but crown-rump length was significantly greater in lambs born to nutrient-restricted ewes [nutrient-restricted, 50.4 +/- 0.4 cm; controls, 48.2 +/- 0.6, cm (p < 0.01)]. Fetal to placental weight ratio was lower in the nutrient-restricted group [nutrient-restricted, 9.51 +/- 0.23; controls, 10.81 +/- 0.39 (p < 0.01)]. A stronger relationship between the total weight of the fetal component of the placental and fetal weight was observed in controls (r2 = 0.50) than in nutrient-restricted ewes (r2 = 0.18). In conclusion, maternal nutrient restriction over the period of rapid placental growth results in a larger placenta and altered placental to fetal weight ratio if ewes are subsequently fed to requirements for the remainder of gestation.

Low birth weight and cardiovascular disease: myth or reality?

The Barker hypothesis proposes a link between low birth weight and adulthood cardiovascular disease. Recent studies have cast doubt on this hypothesis whilst others have proposed an effect of maternal birth weight that may extend to future generations. Thus, the debate on the effect of birth weight in cardiovascular disease continues.

Association of the INS VNTR with size at birth. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood

Size at birth is an important determinant of perinatal survival and has also been associated with the risk for cardiovascular disease and type 2 diabetes in adult life. Common genetic variation that regulates fetal growth could therefore influence perinatal survival and predispose to the development of adult disease. We have tested the insulin gene (INS) variable number of tandem repeats (VNTR) locus, which in Caucasians has two main allele sizes (class I and class III; ref. 3), as a functional candidate polymorphism for association with size at birth, as it has been shown to influence transcription of INS (refs 3-5). In a cohort of 758 term singletons (Avon Longitudinal Study of Pregnancy and Childhood; ALSPAC) followed longitudinally from birth to 2 years, we detected significant genetic associations with size at birth: class III homozygotes had larger mean head circumference (P=0.004) than class I homozygotes. These associations were amplified in babies who did not show postnatal realignment of growth (45%), and were also evident for length (P=0.015) and weight (P=0.009) at birth. The INS VNTR III/II genotype might have bestowed a perinatal survival during human history by conferring larger size at birth. Common genetic variation of this kind may contribute to reported associations between birth size and adult disease.

Consequences of fetal growth restriction

An increasing number of diseases in child and adult life are now thought to have their origins in the fetal period. Central to this predisposition is restriction of fetal growth. During the period reviewed in this article, the associations between adult hypertension and low birthweight were confirmed, and numerous studies have investigated possible mechanisms by which the metabolism of an individual may be programmed by an adverse intrauterine environment. The consequences in adult life of intrauterine undernutrition now highlight prenatal care as one of the most crucial issues in medicine and challenge many aspects of current obstetric decision-making. Research targeting fetal growth and development can be expected to result in improved health at all ages.