Unravelling the fetal origins hypothesis: is there really an inverse association between birthweight and subsequent blood pressure?

Prenatal programming of postnatal productivity and health of livestock: a brief review

Human epidemiological evidence has suggested that metabolic perturbations during fetal life may increase predisposition to cardiovascular disease, type 2 diabetes and obesity in later life. A growing number of controlled experiments on sheep and other large animal species are adding to the already large body of experimental evidence from rat studies in supporting the ‘fetal origins’ hypothesis. Of particular practical relevance are findings that maternal undernutrition in late pregnancy can predispose lambs to glucose intolerance and increased adiposity in early adulthood. This effect may be exacerbated by high energy intakes and limited capacity for muscle growth in undernourished or growth-retarded lambs during early postnatal life. Recent Australian studies have demonstrated the effects of prenatal nutrition on postnatal growth and meat production in beef cattle, and on quantity and quality of wool production in sheep.

Association of birth weight with cardiovascular parameters in adult rats during baseline and stressed conditions

Low birth weight (LBW) due to intrauterine growth restriction (IUGR) in humans is associated with increased blood pressure (BP) in adulthood. In Western countries, IUGR is based on uteroplacental dysfunction. We used an animal model of uteroplacental dysfunction to evaluate this correlation. We hypothesize that IUGR increases baseline BP and alters the BP response to acute stress, which may explain BP differences in previous studies using stressful methods to obtain BP. IUGR was induced by bilateral uterine artery ligation in pregnant Wistar rats according to a modified method of Wigglesworth. BP was measured in the offspring using telemetry, allowing for unstressed measurements in conscious animals. Cardiovascular data were obtained at the age of 12 wk during baseline and acute olfactory stress induced by an ammonia gauze. Rats born after IUGR had a lower birth weight versus controls and did not completely catch up in weight. At baseline, systolic BP (SBP), mean arterial pressure (MAP), and pulse pressure (PP) were elevated in IUGR rats versus controls, by 8, 6, and 5 mm Hg, respectively. There was a strong negative correlation between birth weight and SBP and between birth weight and PP. During acute stress, there was a tendency to reach a higher peak in SBP and to need a longer period to recover in IUGR animals. We conclude that IUGR is associated with increased baseline BP.

Fetal, Developmental, and Parental Influences on Childhood Systolic Blood Pressure in 600 Sib Pairs

BACKGROUND

Little is known about the contribution of maternal and paternal factors to the inverse association between birth weight and later blood pressure in human offspring. A study of within- and between-family associations of birth weight with blood pressure, which collected data on both parents, would address this gap in our knowledge.

METHODS AND RESULTS

The study examined families composed of mother, father, and 2 full sibs delivered between 38 and 41 weeks' gestation within 36 months of each other. A total of 1967 families meeting our inclusion criteria were contacted and 602 were examined (children 5 to 14 years old, 1998 to 2000). Birth weight and gestational age were available from obstetric records. Systolic blood pressure in childhood was inversely associated with birth weight within families (-2.3 mm Hg/kg, 95% CI -4.4 to -0.3) after adjustment for gestational age, sex, height, and weight at examination. The between-family effect (-1.5 mm Hg/kg, -3.1 to 0.0) was strengthened on adjustment for maternal and paternal height and weight, whereas adjustment for paternal and maternal systolic blood pressure at examination independently attenuated the effect.

CONCLUSIONS

The existence of an inverse association of birth weight with systolic blood pressure within families (adjusted for height and weight at examination) demonstrates that factors that vary between pregnancies in the same woman (including fetal genotype) can influence the later blood pressure of offspring. We conclude that this apparent fetal programming effect on blood pressure will not be eliminated solely by interventions aimed at modifying growth and cumulative nutritional status from conception through childhood or other fixed characteristics of future mothers.

Risk of high blood pressure among young men increases with the degree of immaturity at birth

BACKGROUND

Survivors of preterm birth constitute a new generation of young adults, but little is known about their long-term health. We investigated the association between gestational age (GA) and risk of high blood pressure (HBP) in young Swedish men and whether GA modified the risk of HBP; ie, whether HBP was related to being born small for gestational age (SGA).

METHODS AND RESULTS

This population-based cohort study included 329 495 Swedish men born in 1973 to 1981 who were conscripted for military service in 1993 to 2001. Multivariate linear- and logistic-regression analyses were performed. Main outcome measures were systolic and diastolic BPs at conscription. Linear-regression analyses showed that systolic BP increased with decreasing GA (regression coefficient -0.31 mm Hg/wk, P<0.001). Systolic and diastolic BPs both increased with decreasing birth weight for GA, but the association with systolic BP was most evident (regression coefficient -0.67 mm Hg per SD score in birth weight for GA, P<0.001). Compared with men born at term (GA, 37 to 41 weeks), the adjusted odd ratios (95% confidence intervals [CIs]) for high systolic BP (> or =140 mm Hg) were as follows: moderately preterm (33 to 36 weeks), 1.25 (1.19 to 1.30); very preterm (29 to 32 weeks), 1.48 (1.30 to 1.68); and extremely preterm (24 to 28 weeks), 1.93 (1.34 to 2.76). Being SGA was associated only with an increased risk of high systolic BP among men born at 33 weeks or later. The risk estimates for high diastolic BP (> or =90 mm Hg) increased with decreasing GA, but the risk reached significance only among men born moderately preterm.

CONCLUSIONS

Preterm birth, a common pregnancy complication, is a risk factor for HBP in young men. The risk of high systolic BP associated with birth weight for GA is modified by GA, suggesting that perinatal contributions to BP elevation later in life may be induced by different biological pathways.

Origins of the "black/white" difference in blood pressure: roles of birth weight, postnatal growth, early blood pressure, and adolescent body size: the Bogalusa heart study

BACKGROUND

The determinants of differences in blood pressure that emerge in adolescence between black Americans of predominantly African descent and white Americans of predominantly European descent are unknown. One hypothesis is related to intrauterine and early childhood growth. The role of early blood pressure itself is also unclear. We tested whether differences in birth weight and in carefully standardized subsequent measures of weight, height, and blood pressure from 0 to 4 or 5 years were related to black/white differences in blood pressure in adolescence.

METHODS AND RESULTS

Two Bogalusa cohorts who had complete follow-up data on birth weights and early childhood and adolescent anthropometric and blood pressure measures were pooled. One hundred eighty-five children (48 black and 47 white boys and 41 black and 49 white girls) were followed up and studied after 15 to 17 years. Birth weights were a mean 443 and 282 g lower in black boys and girls, respectively, than in whites (P<0.001). Blood pressures in adolescence were 3.4/1.9 and 1.7/0.6 mm Hg higher, respectively, and tracked from early childhood. In regression analyses, birth weight accounted for the ethnic difference in adolescent blood pressure, which was also independently predicted, in decreasing impact order, by adolescent height, adolescent body mass index, and systolic blood pressure at 4 to 5 years and inversely by growth from 0 to 4 to 5 years.

CONCLUSIONS

If these results can be replicated in larger and independent samples, they suggest that efforts to improve intrauterine growth in black infants as well as lessen weight gain in adolescence might substantially reduce excess high blood pressure/hypertension in this ethnic group.

Decline in, and lack of difference between, average birth weights among African and Portuguese babies in Portugal

BACKGROUND

In preliminary data in Portugal, we found that African babies of migrant mothers were heavier than White Portuguese babies born in Lisbon. We investigate whether this pattern is replicated in the national data, and in addition the trends in birth weight in these groups.

METHODS

DESIGN AND SETTING

Births registered between 1995 and 2002 classified by reported nationality of mothers.

PARTICIPANTS

849,595 Portuguese births ('Portuguese' nationality, predominantly of European descent) and 22,463 African births ('Angola', 'Cape Verde', or 'Guinea Bissau, Republic of Guinea or Equatorial Guinea' nationality, predominantly of African origin).

RESULTS

Among Portuguese births, there was a decline in births to teenaged mothers and an increase to mothers aged >or=35 years, with >9 years of education or in a non-manual class, but among African births there was an increase in births to teenaged mothers and a decline to mothers from advantaged socioeconomic backgrounds. Using the Wilcox-Russell method, overall mean birth weights of term Portuguese (3,303, SD 424 g) and African (3297, SD 441 g) babies were not different but the percentage of small preterm births was higher among African (4.7%) than among Portuguese (2.9%) births. Between 1995 and 2002, mean birth weight of term Portuguese babies declined by 58 g (3,334-3,276 g) and of African babies by 57 g (3,341-3,284 g). The left shift of the birth weight distributions was independent of maternal age, parity, and social factors among Portuguese babies, but among African babies the decrease appeared to be associated with socioeconomic advantage.

CONCLUSION

There has been a downward trend in birth weights in Portugal among both Portuguese and African term births, but average birth weights of the two groups were similar.

Correlations of siblings' and mothers' utilisation of primary and hospital health care: a record linkage study in Western Australia

A relationship between maternal and child use of general practitioners (GPs) has been shown to exist for some time, however, the reasons for this relationship are not clear and the extent to which this relationship extends to tertiary care is unknown. The aim of this study was to examine the relationships between the utilisation of health care by siblings and mothers over a 14 year period. A retrospective cohort study of 756 mothers and their 1494 children up to age 14 years was conducted in three general practices in Western Australia. Medicare claims and hospital morbidity records for 1984-1997 were linked using deterministic and probabilistic matching. Generalised Estimating Equations and correlations were used to examine the relationships between the utilisation of primary and hospital health care by family members. Significant correlations were found between hospital admissions of all participants and their GP visits, specialist visits, pathology and diagnostic imaging combined and hospital length of stay. There was a strong association between siblings' use of GPs. A child's rate of GP attendance increased with that of its mother. There was a weak but significant relationship between siblings' use of hospitals, and a child's hospital admission rate increased with that of its mother. It is concluded that there is a strong relationship between siblings' use of GPs and a weaker but still significant association between the hospital admissions of siblings. As expected, there were strong associations between mother and child visits to GPs. There was also an association between a mother's use of hospital and that of her children. This finding reduces the plausibility that the relationships found between utilisation of health care by siblings and mothers can be explained entirely by behavioural factors, and suggests the presence of intergenerational correlation of morbidity.

Blood pressure among very low birth weight (<1.5 kg) young adults

Our objective was to compare the blood pressure of 20-y-old very low birth weight (VLBW; <1.5 kg) individuals with that of normal birth weight (NBW) control individuals. The population included 195 VLBW (92 female and 103 male) and 208 NBW (107 female and 101 male) individuals who were born between 1977 and 1979. Independent effects of birth weight status (VLBW versus NBW) and within the VLBW cohort of intrauterine growth (birth weight z score) were examined via multiple regression analyses. VLBW individuals had a higher mean systolic blood pressure (SBP) than NBW control individuals (114 +/- 11 versus 112 +/- 13 mm Hg). SBP for VLBW female infants was 110 +/- 9 versus NBW 107 +/- 12 and for VLBW male individuals was 118 +/- 11 versus NBW 117 +/- 11 mm Hg. After adjustment for gender, race, and maternal education, the difference in SBP between VLBW and NBW individuals was 1.9 mm Hg but was 3.5 mm after also adjustment for later size (20-y weight and height z scores), which reflects catch-up growth. For female individuals, the difference in SBP between VLBW and NBW individuals was significant both unadjusted and adjusted for later size, whereas for male individuals, the difference was significant only after adjustment for later size. Intrauterine growth did not have a significant effect on SBP within the VLBW group, even after adjustment for later size. VLBW individuals, specifically female individuals, have a higher SBP than NBW control individuals. This is not explained by intrauterine growth failure.

Developmental determinants of blood pressure in adults

Over the past 20 years a large and varied body of research has attempted to make the case for the developmental origins of elevated adult blood pressure (BP). Experimental animal research has identified plausible biological mechanisms through which fetal nutritional insufficiency may affect adult BP. The majority of human epidemiologic studies demonstrate an inverse association of birth weight (the most commonly used marker of fetal nutrition) with adult BP and higher risk of hypertension among individuals with lower weight at birth. The most adverse BP outcomes occur among individuals who were small at birth but relatively large as adults, a finding that suggests a role for postnatal growth. We critically review the literature on proposed mechanisms and epidemiologic evidence for developmental origins of adult BP and hypertension, considering associations with birth weight, maternal nutrition during pregnancy, child growth patterns, and infant feeding.

Birth Characteristics and Risk of High Systolic Blood Pressure in Early Adulthood

BACKGROUND

Although an inverse association between size at birth and blood pressure has been found in several studies, few studies have adjusted for the influence of socioeconomic and familial effects.

METHODS

We investigated whether the association between birth weight and systolic blood pressure in young men is confounded by socioeconomic factors in adolescence or familial factors (ie, common genes and shared environment). Our population-based cohort study comprised 330,768 Swedish men born between 1973 and 1981, and conscripted for military service between 1991 and 2000. The analyses of family effects were restricted to 89,856 siblings from the initial cohort. A high systolic blood pressure at conscription was defined as a systolic blood pressure >/=140 mm Hg. Birth weight for gestational age <-2 standard deviation scores was considered "light for gestational age."

RESULTS

Compared with men who had normal birth weight for gestational age, men who had been born light for gestational age were at increased risk of high systolic blood pressure (odds ratio = 1.14; 95% confidence interval = 1.07-1.22), even after adjustment for important confounders such as socioeconomic status. The increase in risk of high systolic blood pressure related to 1 standard deviation score decrease in birth weight for gestational age was similar within families (1.08; 1.04-1.12) and between families (1.05; 1.03-1.08).

CONCLUSIONS

This study suggests that low birth weight for gestational age slightly increases the risk of high systolic blood pressure, and that the association appears not to be confounded by socioeconomic or familial effects.

Birthweight and blood pressure in five European birth cohort studies: an investigation of confounding factors

BACKGROUND

It has been suggested that the association between birthweight and blood pressure has been overstated as a result of publication bias and, within studies, a lack of adjustment for potentially important maternal and socioeconomic confounding factors and 'overadjustment' for current body size. This study investigates the impact of potential confounding variables on the birthweight-blood pressure association in birth cohort studies from different time periods and geographical locations in Europe.

METHODS

Data from five European birth cohort studies (from Finland, the UK, and the Faroe Islands) taking part in the European Birth-Lifecourse-Studies (EURO-BLCS) project were analysed. Birthweight was measured at birth in all cohorts and confounding variable information was collected prospectively at subsequent follow-ups in all cohorts. Regression models were used to assess the unadjusted association between birthweight and blood pressure and then to assess the impact of potential maternal and socioeconomic confounding variables and adjustment for later body size. Analyses were carried out in the same way across all five cohorts.

RESULTS

Birthweight was consistently negatively associated with systolic blood pressure (SBP) across all cohorts. Gestational age and possibly maternal pre-pregnancy weight, but not socioeconomic status, may be important confounding factors of the relationship between birthweight and SBP. The size of the birthweight-SBP association in adulthood may be larger than in childhood before adjustment for current body size, although a cohort effect cannot be ruled out.

CONCLUSION

This study highlights the value of future cross-cohort comparisons in the investigation of the foetal origins of adult disease.

Is blood pressure increased 19 years after intrauterine growth restriction and preterm birth? A prospective follow-up study in The Netherlands

OBJECTIVE

To determine whether intrauterine growth restriction (IUGR) is a predisposing factor for high blood pressure (BP) in 19-year-olds who were born (very) preterm.

METHODS

A prospective follow-up study was conducted at age 19 in individuals who born preterm in the Netherlands in 1983. Systolic, diastolic, and mean BP values and plasma renin activity concentration were obtained in 422 young adults who were born with a gestational age (GA) <32 weeks. BP values were also measured in 174 individuals who born with a GA of > or =32 weeks and a birth weight of <1500 g.

RESULTS

An increased prevalence of hypertension and probably also of prehypertensive stage was found. IUGR, birth weight, GA, and plasma renin activity were not associated with BP. Current weight and BMI were the best predicting factors for systolic BP at the age of 19 years.

CONCLUSIONS

The prevalence of hypertension is high in individuals who were born preterm when compared with the general population. In the individuals who were born very preterm, no support to the hypothesis that low birth weight is associated with increased BP at young adult age can be given.

Glomerular Number and Function Are Influenced by Spontaneous and Induced Low Birth Weight in Rats

A link exists between low birth weight and diseases in adulthood, such as hypertension, cardiovascular disease, and insulin resistance. Intrauterine growth restriction (IUGR) has been used to explain this association and has been shown to lead to a nephron endowment in humans. A reduction in glomerular number has been described in animal models with induced low birth weight as well but not in animals with spontaneous low birth weight. It therefore is debatable whether the models are suitable. The effect on glomerular number and size was studied in rats with naturally occurring IUGR and experimental IUGR, induced by bilateral uterine artery ligation. Design-based stereologic methods were used. Urinary protein excretion was determined as a measure of renal damage. Results showed a decrease of approximately 20% in glomerular number in both groups of IUGR (control 35,400, naturally occurring IUGR 30,900, and experimental IUGR 28,000 glomeruli per kidney). Mean glomerular volume was increased in both IUGR groups, which was associated with an increased proteinuria. It is concluded that IUGR leads to a nephron endowment with a compensatory glomerular enlargement. This compensation is associated with more proteinuria in the long run. Uterine artery ligation in the pregnant rat is a suitable model to study the effects of IUGR on the kidney.

Prenatal exposure to maternal undernutrition induces adult cardiac dysfunction

An adverse environmental experience of the growing fetus may lead to permanent changes in the structure and function of organs that may predispose the individual to chronic diseases in later life; however, nothing is known about the occurrence and mechanisms of heart failure. We employed a rat model in which pregnant dams were fed diets containing either 180 g (normal) or 90 g (low) casein/kg for 2 weeks before mating and throughout pregnancy. The ejection fraction (EF) of the pups exposed to the low-protein (LP) diet was severely depressed in the first 2 weeks of life and was associated with an increase in cardiomyocyte apoptosis. This early depressed cardiac function was followed by progressive recovery and normalization of the EF of the offspring in the LP group. The left ventricular (LV) internal diameters were increased between 24 h and 84 d (12 weeks) of age in the LP-exposed group. Although between 3 d and 2 weeks of age the LV wall of the heart in the LP group was thinner, a progressive increase in LV wall thickness was seen. At 40 weeks of age, although the EF was normal, a two-fold elevation in LV end-diastolic pressure, reduced cardiac output, decreased maximum rates of contraction and relaxation, and reduced mean arterial pressure were observed. Our findings demonstrate that exposure of the developing fetus to a maternal LP diet programs cardiac dysfunction in the offspring in later life.

Animal models of programming: early life influences on appetite and feeding behaviour

Epidemiological observations of associations between early life nutrition and long-term disease risk have prompted detailed experimental investigation of the biological basis of programming. Studies using rodent or large animal models have clearly established the biological plausibility of nutritional programming and are now yielding important information on underlying mechanisms. Nutritional interventions in pregnancy, including global food restriction, protein restriction, micronutrient restriction and excess fat feeding, determine a consistent cluster of disorders in the resulting offspring. The common association of such diverse nutritional disturbances with hypertension, glucose intolerance and adiposity suggests that a small number of simple common mechanisms are active in response to fetal nutrient imbalance. Studies of rodent models indicate that fetal undernutrition determines adult adiposity. It is unclear whether the increase in central adiposity is related to increased food intake or reduced energy expenditure, although evidence exists to suggest that both may act together. Rats subject to intrauterine protein restriction exhibit increased preference for high fat foods. Feeding of energy dense foods to rats that were undernourished in utero promotes a greater degree of obesity than is noted in animals subject to adequate nutrition in fetal life. There is evidence to suggest that programming of appetite may stem from remodelling of hypothalamic structures that control feeding and programming of the expression of genes involved in responses to orexogenic hormones. The early life programming of appetite and obesity is a complex phenomenon and our understanding of how maternal nutrition determines later energy balance is at a very early stage.

The association of birthweight and contemporary size with insulin resistance among children from Estonia and Denmark: findings from the European Youth Heart Study

OBJECTIVES

To assess the associations of birthweight, contemporary body mass index and height with insulin resistance in children.

DESIGN

Cross-sectional study.

PARTICIPANTS

From Estonia (n = 1174) and Denmark (n = 1018), 2192 school children aged 9 and 15 years were randomly selected.

MAIN OUTCOMES

Insulin resistance (homeostasis model assessment), triglyceride levels, high-density lipoprotein cholesterol and systolic blood pressure.

RESULTS

There was an inverse association between birthweight and insulin resistance and a positive association between contemporary body mass index and insulin resistance. With adjustment for maternal and paternal educational level, income, smoking and body mass index, an increase of one unit of sex, age and country standardized body mass index z-score was associated with a 5% (95% CI: 2, 7%) increase in homeostasis model assessment (HOMA) score and a one-unit z-score increase in birthweight with a 2% (95% CI: 0, 5%) decrease in HOMA score. In the 9-year-old age group, height was positively associated with insulin resistance [for a one-unit increase in height z-score HOMA score increased by 30% (95% CI: 14, 50%)], but in the 15-year-old age group there was no association between height and insulin resistance (4% (95% CI: -5, 14%), P for interaction with age group = 0.001). For both ages, those in the lowest third of the birthweight distribution and highest third of the body mass index distribution were most insulin resistant and, among 9-year olds, those in the lowest third of the birthweight distribution and highest third of the height distribution were most insulin resistant. Birthweight was only inversely associated with systolic blood pressure when adjustment was made for either contemporary body mass index or height and there was no association between birthweight and high-density lipoprotein or triglyceride concentrations.

CONCLUSIONS

Taken together, these results suggest that a slow intrauterine growth trajectory and/or a fast post-natal growth trajectory is associated with greater insulin resistance in childhood.

Ethnicity and renal disease

BACKGROUND

Sexual function is one aspect of physical functioning. Sexual dysfunction, no matter the etiology, could cause distress. In female hemodialysis patients, sexual problems have often been neglected in clinical performance and research.

METHODS

We conducted this study by use of self-reported questionnaires. A total of 578 female hemodialysis patients in northern Taiwan were included in this study. Demographic data, comorbid diseases, medications in use, biochemical, and hematologic parameters were analyzed. All patients were asked to complete by themselves three questionnaires: (1) the Index of Female Sexual Function (IFSF) to assess sexual function; (2) the Beck Depression Inventory (BDI) (Chinese version) to rate the severity of depressive symptoms; and (3) the 36-item Short Form Health Survey Questionnaire (SF-36, Taiwan Standard Version 1.0) to survey their quality of life.

RESULTS

A total of 138 female patients were enrolled into further analysis. The mean age was 48.7 +/- 11.2 years old. The mean IFSF score was 24.5 +/- 9.3. Age, BDI score, and serum triglyceride levels were the independent factors of dysfunction in each sexual functional dimension. Patients with higher IFSF scores had significantly higher scores in physical functioning and mental health (P= 0.007 and 0.018, respectively). Patients with higher intercourse satisfaction had significantly higher general health scores (P= 0.001).

CONCLUSION

Sexual dysfunction is frequent in the female hemodialysis population. It is strongly associated with increasing age, dyslipidemia, and depression. The subjects with sexual dysfunction had poorer quality of life. The diagnosis and treatment of sexual dysfunction should be included in the clinical assessment.

Association of pulse waveform characteristics with birth weight in young adults

OBJECTIVE

An association between birth weight and blood pressure has been reported in many studies, but the strength of this association has been disputed. Birth weight could, however, be associated with alterations in the proximal arterial tree that have little effect on blood pressure. The objective of this study was to examine the relationship between birth weight and characteristics of the proximal arterial tree determined by pulse wave analysis.

METHODS

An optically derived digital volume pulse was used to obtain indices of pressure wave reflection (reflection index; RI) determined by characteristics of small/medium sized arteries and of large artery stiffness (stiffness index; SI) in healthy young adults (n = 220, 111 women, aged 16-26 years). Birth weight was obtained from maternal recall.

RESULTS

Diastolic blood pressure was significantly correlated with birth weight (P < 0.001) but birth weight accounted for only 5% of the variance in diastolic blood pressure. RI was significantly correlated with birth weight in women (r = -0.33, P < 0.001) but not in men, and there was a significant interaction between birth weight and sex (P < 0.001). SI was significantly independently correlated with birth weight in both men and women (r = -0.41 and -0.49, each P < 0.0001) and birth weight accounted for 17% of the overall (men and women) variance in SI.

CONCLUSIONS

These results suggest a close association between birth weight and characteristics of the arterial tree proximal to resistance vessels in young adults and a sex-specific association with characteristics influencing arterial pressure wave reflection.

Embryonic and fetal programming of physiological disorders in adulthood

In the past decade, data from numerous epidemiological studies have indicated strong inverse associations between birth weight and risk of coronary heart disease, hypertension, type 2-diabetes, and other diseases in adulthood. The "Barker hypothesis" thus postulates that a number of organ structures and functions undergo programming during embryonic and fetal life. This developmental programming determines the set points of physiological and metabolic responses in adult life. Alterations of nutrient availability during gestation may lead to developmental adaptations, via hormonal maneuvers by the embryo and fetus that readjust these set points. These adaptive measures have short-term benefits to the embryo and fetus, so that the newborn will be better prepared for the adverse environment (e.g., undernutrition). However, adequate nutritional support during postnatal life that enables catch-up growth may create metabolic conflicts that predispose the adult to aberrant physiological functions and, ultimately, increased risk of disease. It is plausible that other adverse in utero conditions, including exposure to developmental toxicants, may similarly alter adult disease susceptibility. This article provides an overview of the Barker hypothesis, its supporting evidence, the current advances in understanding the biological mechanisms underlying this phenomenon, and its implications for developmental toxicology.

Growth patterns of the heart and kidney suggest inter-organ collaboration in facultative fetal growth

Maternal smoking during pregnancy has been associated with a number of negative sequelae among offspring, including elevated postnatal blood pressure. While animal studies have described organ level alterations with smoke exposure, human data have been more limited. Thirty-four healthy maternal/fetal pairs (24 nonsmokers, 10 smokers) participated in a longitudinal growth study from the thirteenth week of pregnancy to document fetal kidney and heart growth trajectories and morphology. Curve fitting followed by a mixed model for repeated measures identified significantly different growth patterns in kidney width, thickness, length, and volume growth with exposure: the smoke-exposed fetal kidney was wide and thick compared to the unexposed kidney during the second and early third trimester, declining to proportionately thin kidneys for length and width subsequently. Cardiac growth in width and volume followed a reverse pattern: a surge in cardiac volume occurred after 30 weeks with acceleration in cardiac width, resulting in a heart that was wide for length and for fetal weight. Smoke exposure altered fetal growth in size and timing of the heart and kidneys during midgestation, with changes in organ morphology suggesting compensatory growth. These are the first data providing anatomical evidence of altered renal/cardiac volume relationships that may provide a mechanism to previously reported sequelae of in utero smoke exposure. They suggest that cell-level adaptive responses to hypoxia and/or chemical insults are operative and illustrate the importance of longitudinal ultrasound to directly assess the organ-level growth response of the human fetus to a prenatal stress, in lieu of relying on birth outcome measures.

Cardiovascular risk factors after antenatal exposure to betamethasone: 30-year follow-up of a randomised controlled trial

BACKGROUND

Antenatal betamethasone treatment is widely used for the prevention of neonatal respiratory distress syndrome in preterm infants and substantially reduces neonatal mortality and morbidity. Fetal exposure to excess glucocorticoids has been proposed as one of the core mechanisms of the fetal origins of adult disease hypothesis. We assessed whether antenatal exposure to betamethasone for the prevention of neonatal respiratory distress syndrome affects cardiovascular risk factors at 30 years of age.

METHODS

We followed up at age 30 years 534 individuals whose mothers participated in a double-blind, placebo-controlled, randomised trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome. Mothers received two doses of betamethasone or placebo given by intramuscular injection 24 h apart. Follow-up assessments included anthropometry; measurement of blood pressure, blood lipids (after overnight fasting), and early morning cortisol levels; and a 75 g oral glucose tolerance test.

FINDINGS

There were no differences between those exposed to betamethasone and to placebo in body size, blood lipids, blood pressure, plasma cortisol, prevalence of diabetes, or history of cardiovascular disease. After a 75 g oral glucose tolerance test, participants exposed to betamethasone had higher plasma insulin concentrations at 30 min (60.5 vs 52.0 mIU/L; ratio of geometric means 1.16 [95% CI 1.03 to 1.31], p=0.02) and lower glucose concentrations at 120 min (4.8 vs 5.1 mmol/L; difference -0.26 mmol/L [-0.53 to 0.00], p=0.05) than did those exposed to placebo.

INTERPRETATION

Antenatal exposure to betamethasone might result in insulin resistance in adult offspring, but has no clinical effect on cardiovascular risk factors at 30 years of age. Thus, obstetricians should continue to use a single course of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome.

Longitudinal study of birth weight and adult body mass index in predicting risk of coronary heart disease and stroke in women

OBJECTIVES

To determine whether birth weight and adult body size interact to predict coronary heart disease in women, as has been observed for men. To determine whether birth weight and adult body size interact to predict risk of stroke.

DESIGN

Longitudinal cohort study.

SETTING AND PARTICIPANTS

66,111 female nurses followed since 1976 who were born of singleton, term pregnancies and reported their birth weight in 1992.

MAIN OUTCOME MEASURES

1504 events of coronary heart disease (myocardial infarction or sudden cardiac death) and 1164 strokes.

RESULTS

For each kilogram of higher birth weight, age adjusted hazard ratios from prospective analysis were 0.77 (95% confidence interval 0.69 to 0.87) for coronary heart disease and 0.89 (0.78 to 1.01) for total stroke. In combined prospective and retrospective analysis, hazard ratios were 0.84 (0.76 to 0.93) for total stroke, 0.83 (0.71 to 0.96) for ischaemic stroke, and 0.86 (0.66 to 1.11) for haemorrhagic stroke. Exclusion of macrosomic infants (> 4536 g) yielded stronger estimates. Risk of coronary heart disease was especially high for women who crossed from a low centile of weight at birth to a high centile of body mass index in adulthood. The association of lower birth weight with increased risk of stroke was apparent across categories of body mass index in adults and was not especially strong among heavier women.

CONCLUSIONS

Higher body mass index in adulthood is an especially strong risk factor for coronary heart disease among women who were small at birth. In this large cohort of women, size at birth and adiposity in adulthood interacted to predict events of coronary heart disease but not stroke events.

Illness perceptions in coronary heart disease. Sociodemographic, illness-related, and psychosocial correlates

OBJECTIVES

This study examined illness perceptions (IP) and their correlates in coronary heart disease (CHD).

METHODS

The sample of the questionnaire study (n = 3130 at baseline and n = 2745 at 1-year follow-up, aged 45-74 years) was drawn from the drug reimbursement register, which covers persons with various drug-treated conditions. Independent variables were CHD severity and history, vicarious experiences, and psychosocial resources.

RESULTS

Men attributed their CHD more often to risk behaviours and internal factors (own attitude/behaviour), while women perceived stress as the cause of their CHD more often. Women also perceived more symptoms associated with CHD but reported less severe consequences. CHD severity was the most important correlate of IP and also predicted change in IP at the follow-up. Stronger perceived competence was related to weaker illness identity, stronger control/cure, and less severe consequences.

CONCLUSIONS

Although disease-related factors are powerful correlates of CHD-related illness cognitions, also social and psychosocial factors are related to IP.

Fetal origins of adult vascular dysfunction in mice lacking endothelial nitric oxide synthase

Epidemiological studies have shown increased incidence of hypertension and coronary artery disease in growth-restricted fetuses during their adult life. A novel animal model was used to test the hypothesis regarding the role of an abnormal uterine environment in fetal programming of adult vascular dysfunction. Mice lacking a functional endothelial nitric oxide synthase (NOS3−/−KO, where KO is knockout) and wild-type (WT) mice (NOS3+/+WT) were crossbred to produce homozygous NOS3−/−KO, maternally derived heterozygous (NOS3+/−mat, mother with NOS3 deficiency), paternally derived heterozygous (NOS3+/−pat, normal mother), and NOS3+/+WTlitters. Number of fetuses per litter was smaller in NOS3−/−KOand NOS3+/−matcompared with NOS3+/−patand NOS3+/+WTmice. Adult female mice from these litters (7–8 wk old) were killed, and ring preparations of carotid and mesenteric arteries were mounted in a wire myograph to evaluate the passive and reactive vascular characteristics. Slope of the length-tension plot (a measure of vascular compliance) was increased, and optimal diameter (as calculated by Laplace equation) was decreased in NOS3−/−KOand NOS3+/−matcompared with NOS3+/−patand NOS3+/+WTmice. Acetylcholine caused vasorelaxation in NOS3+/−patand NOS3+/+WTand contraction in NOS3−/−KOand NOS3+/−matmice. Responses to phenylephrine and Ca2+were increased in NOS3−/−KOand NOS3+/−matcompared with NOS3+/−patand NOS3+/+WTmice. Relaxation to isoproterenol was decreased in NOS3−/−KOand NOS3+/−matvs. NOS3+/−patand NOS3+/+WTmice. Abnormalities in the passive and reactive in vitro vascular properties seen in NOS+/−matthat developed in a NOS3-deficient maternal/uterine environment compared with the genetically identical NOS3+/−patmice that developed in a normal environment are the first direct evidence in support of a role for uterine environment in determining vascular function in later life.

Early life determinants of adult blood pressure

PURPOSE OF REVIEW

While treating high blood pressure in middle age is beneficial in terms of reducing the occurrence of cardiovascular disease, treated and well controlled hypertensive adults still have a substantial excess mortality and reduced survival compared with normotensives. Therefore, identification of the means of preventing hypertension in earlier life is an important objective. There is increasing evidence that adult blood pressure is determined by a range of characteristics from the intrauterine period, through infancy and childhood. The purpose of this review is to provide a summary of the current evidence concerning the early life determinants of adult blood pressure.

RECENT FINDINGS

Children from poorer socioeconomic positions, those whose mothers experience pregnancy-induced hypertension, those whose mothers smoke throughout pregnancy, those with low birthweight, who are not breast-fed, who have high sodium diets in infancy and who are obese in childhood or adolescence tend to have higher blood pressure in adulthood. However, the mechanisms linking these early life factors to later blood pressure and the most appropriate means of preventing adult hypertension by intervening in early life are unclear.

SUMMARY

There is clear evidence that early life factors are important determinants of adult blood pressure. However, there is a need for randomized trials with sufficient resources for long-term follow-up to assess the effects that interventions such as preventing pregnancy-induced hypertension, reducing maternal smoking, increasing breast-feeding, reducing salt consumption in infancy and preventing childhood obesity have on adult blood pressure and cardiovascular disease.

Birth weight, hypertension and ‘white coat’ hypertension: size at birth in relation to office and 24-h ambulatory blood pressure

We investigated the association of size at birth with hypertensive status defined by office blood pressure (BP) and 24-h ambulatory BP monitoring in a historical cohort study of 736 men born 1920-1924 and examined at age 70 years. Office BP was measured after 10-min supine rest with a sphygmomanometer, ambulatory BP was recorded with Accutracker 2, and anthropometric and other measurements were taken at a clinic. Birth weight and gestational age were abstracted from the men's birth records. A total of 24% of the men were treated for hypertension at the time of the study. Among not treated subjects, there was a weak positive association of birth weight with daytime and 24-h diastolic ambulatory BP. In subjects treated for hypertension, both office and ambulatory BP were inversely related to birth weight, although these associations were not statistically significant. Birth weight did not show significant association with sustained hypertension (elevated office and daytime ambulatory BPs) but showed a strong and statistically significant inverse association with "white coat" hypertension (elevated office BP and normal daytime ambulatory BP) when adjusted for concurrent body mass index (odds ratios 1.91, 1.59, 1 and 1.21 from lowest to highest quartile of birth weight, P-value for trend 0.035). We conclude that BP measured by 24-h-ambulatory monitoring is not related to birth weight in a pattern previously reported for office BP and that factors related to growth in utero are particularly related to higher risk of "white coat" hypertension.

Racial disparities in the association of foetal growth retardation to childhood blood pressure

BACKGROUND

Foetal growth retardation (FGR), defined as less than the 10th percentile of birth weight for gestational age, is reported to be an important contributor to hypertension and cardiovascular disease in children and adults, but findings are not consistent. For this reason we re-examined the role of FGR in childhood blood pressure.

METHODS

We performed univariate and multivariate analyses on data gathered from 262 children, age 5 years, born to mothers at risk for pre-term delivery or FGR infant. The characteristics of the mothers and the children were evaluated using Student's t-test. Rates and proportions were compared using either chi-square or Fisher's exact test. Linear regression models evaluated the effect of birth weight and body mass index on systolic and diastolic blood pressure. Multivariate linear regression was used to model the effects of FGR, gestational age, body mass index, race, gender, maternal smoking, maternal gestational diabetes on blood pressure while adjusting for possible confounders.

RESULTS

Systolic blood pressure was inversely associated with birth weight in white children while a small direct association was noted in African Americans. Body mass index was positively associated with systolic blood pressure in both groups. Multiple linear regression analyses showed FGR and early gestational age were associated with higher blood pressure in white but not African American children, accounting for a 13.2 mmHg difference between FGR and appropriate for gestational age groups. Blood pressure in African Americans was strongly affected by maternal gestational diabetes and smoking.

CONCLUSIONS

Birth weight influences childhood blood pressure but the effects may vary depending on ethnic group. The relative importance of birth weight on blood pressure may depend on other prenatal and post-partum risks.

Calorie and protein-enriched formula versus standard term formula for improving growth and development in preterm or low birth weight infants following hospital discharge

BACKGROUND

Preterm and low birth weight infants are often growth-restricted at hospital discharge. Feeding infants post-hospital discharge with calorie and protein-enriched formula milk might facilitate "catch-up" growth and improve development.

OBJECTIVES

To review the evidence from randomised controlled trials that feeding following hospital discharge with calorie and protein-enriched formula compared with standard term formula improves growth and development for preterm or low birth weight infants.

SEARCH STRATEGY

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2004), MEDLINE (1966 - December 2004), EMBASE (1980 - December 2004), CINAHL (1982 - December 2004), conference proceedings, and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared the effect of feeding preterm or low birth weight infants post-hospital discharge with calorie and protein-enriched formula compared with standard term formula.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two authors, and synthesis of data using weighted mean difference and a fixed effects model for meta-analysis.

MAIN RESULTS

We found six trials that were eligible for inclusion. These recruited a total of 424 infants and were generally of good methodological quality. These trials found little evidence that feeding with calorie and protein-enriched formula milk affected growth and development. Because of differences in the way individual trials measured and presented outcomes, data synthesis was limited. Meta-analysis of data from two trials found a statistically significant effect on crown-heel length at 18 months post-term (weighted mean difference 9.7 millimetres (95% confidence interval 3.2 to 16.2)), but not on weight or head circumference. Meta-analysis of data from the two trials that assessed neurodevelopment at 18 months post-term did not reveal a statistically significant difference in either Bayley Mental Development Index (weighted mean difference 0.23 (95% confidence interval -2.99 to 3.45)) or Psychomotor Development Index (weighted mean difference 0.56 (95% confidence interval -1.95 to 3.07)). There are not yet any data on growth or development through later childhood.

AUTHORS' CONCLUSIONS

The limited available data do not provide strong evidence that feeding preterm or low birth weight infants following hospital discharge with calorie and protein-enriched formula compared with standard term formula affects growth rates or development up to 18 months post-term.

Developmental origins of the metabolic syndrome: prediction, plasticity, and programming

The "fetal" or "early" origins of adult disease hypothesis was originally put forward by David Barker and colleagues and stated that environmental factors, particularly nutrition, act in early life to program the risks for adverse health outcomes in adult life. This hypothesis has been supported by a worldwide series of epidemiological studies that have provided evidence for the association between the perturbation of the early nutritional environment and the major risk factors (hypertension, insulin resistance, and obesity) for cardiovascular disease, diabetes, and the metabolic syndrome in adult life. It is also clear from experimental studies that a range of molecular, cellular, metabolic, neuroendocrine, and physiological adaptations to changes in the early nutritional environment result in a permanent alteration of the developmental pattern of cellular proliferation and differentiation in key tissue and organ systems that result in pathological consequences in adult life. This review focuses on those experimental studies that have investigated the critical windows during which perturbations of the intrauterine environment have major effects, the nature of the epigenetic, structural, and functional adaptive responses which result in a permanent programming of cardiovascular and metabolic function, and the role of the interaction between the pre- and postnatal environment in determining final health outcomes.

Children in South Asia Have Higher Body Mass–Adjusted Blood Pressure Levels Than White Children in the United States

BACKGROUND

Blood pressure during childhood is an established predictor of adult blood pressure, which in turn increases mortality as a result of cardiovascular disease. Adult South Asian populations are particularly predisposed to cardiovascular disease compared with whites, but the prevalence of high blood pressure and determinants of blood pressure in South Asian children have not been explored or compared with those of white children.

METHODS AND RESULTS

Analyses were performed on 5641 South Asian children 5 to 14 years old included in the nationally representative National Health Survey of Pakistan (NHSP) (1990-1994) and on 4756 white children 5 to 14 years old included in Third National Health and Nutrition Examination Survey (NHANES III) (1988-1994). Anthropometric measurements were obtained. Blood pressure was measured twice in the seated position with a mercury sphygmomanometer and an appropriate-size cuff. High blood pressure was defined as a systolic or diastolic blood pressure level that was > or =95th percentile of age-, sex-, and height-percentile-specific reference level for the US population. Mean body mass index (BMI)-adjusted blood pressure values were compared among children in 2 data sets by use of linear regression analysis. The overall prevalence (95% CI) of high blood pressure in South Asian children 5 to 14 years old was 12.2% (11.3% to 13.1%): 15.8% (14.5% to 17.1%) in boys and 8.7% (7.6% to 9.8%) in girls. This is in sharp contrast with the predicted 5% prevalence of high blood pressure in children in the United States (P<0.001). The mean BMI-adjusted systolic blood pressure levels (SD) were 100 (11) versus 99 (11) mm Hg (P<0.001), and diastolic blood pressure levels (SD) were 63 (10) versus 52 (12) mm Hg (P<0.001) in NHSP versus NHANES III, respectively.

CONCLUSIONS

South Asian children have higher body-mass-adjusted blood pressure levels than white children in the United States. Further studies are needed to determine factors responsible for these differences. Immediate attention is needed to address high blood pressure and its risk factors in native South Asian children.

Are early life factors responsible for international differences in adult blood pressure? An ecological study

BACKGROUND

Although low birthweight has been related to higher mean blood pressure in individuals, there have been very few studies on the contribution of the 'fetal origins hypothesis' to international variations in mean blood pressure.

METHODS

Standardized data on mean blood pressure levels in adults aged 20-29 years (available from the INTERSALT study countries) were related to data on mean birthweight and infant mortality rates (IMRs) approximately 25 years earlier (available from the World Health Organization and the United Nations statistics for 24 of these countries).

RESULTS

Population mean systolic pressure was inversely correlated with IMR (r = -0.66, P < 0.001) and positively correlated with mean birthweight (r = 0.36, P = 0.108). These correlations were little affected by adjustment either for current body mass index or for current sodium, potassium, and alcohol intake.

CONCLUSIONS

The directions of these associations suggest that low mean birthweight and high infant mortality are not important determinants of high population mean adult blood pressure levels.

Current concepts in intrauterine growth restriction

Regulation of fetal growth is multifactorial and complex. Diverse factors, including intrinsic fetal conditions as well as maternal and environmental factors, can lead to intrauterine growth restriction (IUGR). The interaction of these factors governs the partitioning of nutrients and rate of fetal cellular proliferation and maturation. Although IUGR is probably a physiologic adaptive response to various stimuli, it is associated with distinct short- and long-term morbidities. Immediate morbidities include those associated with prematurity and inadequate nutrient reserve, while childhood morbidities relate to impaired maturation and disrupted organ development. Potential long-term effects of IUGR are debated and explained by the fetal programming hypothesis. In formulating a comprehensive approach to the management and follow-up of the growth-restricted fetus and infant, physicians should take into consideration the etiology, timing, and severity of IUGR. In addition, they should be cognizant of the immediate perinatal response of the growth-restricted infant as well as the childhood and long-term associated morbidities. A multi disciplinary approach is imperative, including early recognition and obstetrical management of IUGR, assessment of the growth-restricted newborn in the delivery room, possible monitoring in the neonatal intensive care unit, and appropriate pediatric follow-up. Future research is necessary to establish effective preventive, diagnostic, and therapeutic strategies for IUGR, perhaps affecting the health of future generations.

Further thoughts regarding evidence offered in support of the 'Barker hypothesis'

The original objection to the paper by Kwong et al. was that the use of an inappropriate (between-pup) estimate of experimental error had exaggerated the importance of the maternal nutrition effect. From the group's most recent response, it has been possible to regenerate the raw data and carry out a further detailed analysis. It is apparent that despite now using a more sophisticated statistical tool, Kwong et al. have still, in effect, used the between-pup error, thus repeating the previous, probably exaggerated, finding. It is maintained that the nutrition effect should be studied using the between-rat variation, which then provides a result that is a good deal less emphatic. Further, it is felt that there is a very important point of principle involved in this dispute, relating to the rigorous analysis of hierarchical data, particularly in small studies.

The relation between birth weight and intima-media thickness in middle-aged adults

BACKGROUND

Birth weight has been found to be inversely associated with the risk of coronary heart disease and stroke, although the mechanisms for this association remain unclear. Here, we investigate the relation between reported birth weight and atherosclerosis in middle age.

METHODS

We included the 9817 participants (age 44-65) in the Atherosclerosis Risk in Communities (ARIC) study who were neither a twin nor born prematurely. Carotid atherosclerosis was assessed as intima-media thickness measured by B-mode ultrasound. We studied the association with recalled exact birth weight, and for those unable to recall exact birth weight, with recalled birth weight category.

RESULTS

Mean intima-media thickness (+/- standard deviation) was 0.73 +/- 0.17 mm. Mean birth weight for the 4635 participants recalling exact birth weight was 3.49 +/- 0.71 kg. A further 4946 participants recalled birth weight category, with 4730 (96%) reporting "medium" birth weight. In univariate analysis, birth weight and intima-media thickness were positively related. However, adjustment for confounding factors reduced the association to only a 0.004 mm higher intima-media thickness (95% CI = - 0.003 to 0.011) mm per 1 kg of birth weight. The same pattern of univariate positive relationship and attenuation with adjustment was seen for birth weight category and intima-media thickness. There was no evidence of interaction between adult body mass index (BMI) and birth weight, or of interaction between category of adult BMI and birth weight category. An inverse relation between birth weight category and intima-media thickness was seen only for those in the lowest category of adult BMI (BMI <25 kg/m).

CONCLUSIONS

We found no evidence of a clinically significant relation between birth weight and carotid atherosclerosis.

Longterm Effects of Pre- and Postnatal Exposure to Low and High Dietary Protein Levels

The purpose of this short review is to summarize the available evidence from observational studies and rodent models for an association between maternal protein intake, birth weight, pre- and post-weaning body mass gain and adult body fatness in the offspring.

Studies of twins: what can they tell us about the fetal origins of adult disease?

There has been much interest in evidence that people with lower birthweight have higher risk of adult cardiovascular disease, but the causal pathways underlying such observations are uncertain. Study of twins offers an opportunity to shed light on the underlying causal pathways, in particular by investigating the role of 'shared' factors vs. factors affecting each individual fetus. This involves comparing results of within-cohort vs. within-pair analyses. Twins share many factors during gestation but birthweight discordance (difference in birthweight within a twin pair) cannot be determined by these shared factors and must relate to factors affecting growth of each individual fetus. If associations seen in a cohort of twins remain in within-pair analyses, then factors specific to each individual must be involved in the underlying causal pathways. Conversely, if the relationships disappear or substantially diminish in within-pair analyses, then factors common to the pair must be involved. Comparison of findings in monozygotic vs. dizygotic twins may provide insights into the role of genetic factors, although issues related to chorionicity need to be taken into account. We tabulate published data and conclude that differences in methodology and analyses preclude informative meta-analysis, and that analysis of pooled data would provide more useful information.

A discussion of some statistical methods for separating within-pair associations from associations among all twins in research on fetal origins of disease

Twin data can be used to gain insights into the origin of associations between factors arising in fetal life and the risk of later disease. This is because twin data afford an opportunity to conduct paired analyses that take the influence of shared factors into account. When an association that is present in an unpaired analysis is present also in a paired analysis, there is evidence that the causal pathway linking the fetal factor and the disease may have a fetal origin. If the association disappears in the paired analysis, there is evidence that it may have has arisen from a shared source such as the mother. The relevant factors include diet and socio-economic status. There are several statistical approaches to this. The simplest involves comparing, say, a coefficient from a regression of an outcome on a fetal factor for all subjects in a twin sample, with the coefficient obtained from regressing the within-pair difference in the outcome on the within-pair difference in the fetal factor. Alternative approaches involve simultaneously estimating regression parameters for between- and within-pair components. These approaches permit similar inferences about whether the association is due to individual (fetal) or shared (maternal) factors, and are valid in the circumstances that non-shared factors missing from the regression model do not influence the regression estimates.

Statistical analysis of data in support of the Barker hypothesis, advantages of using random effects regression model in hierarchical data

In a recent note by Walters and Edwards (2004), the authors argued that summary statistics should be used in analysing hierarchical data from our earlier analysis of a rat model of developmental programming and the Barker hypothesis (Kwong et al., 2000, 2004). We reiterate here why such a view is inappropriate. Hierarchical data merits multilevel analysis using a 'random effects' model to enable estimation of variances at different levels and easy assessment of other parameters in a complex data structure.

The fetal, neonatal, and infant environments-the long-term consequences for disease risk

The developmental origins of health and disease can be understood by reference to the fundamentals of developmental plasticity. It is essential to distinguish between those environmental effects acting during development that are disruptive from those that have adaptive value. The latter are likely to underpin programming and the developmental origins of adult disease. It is suggested that greater disease risk is created by a mismatch between the environment predicted during the plastic phase of development and the actual environment experienced in the postplastic phase. This plastic phase extends from conception to after birth at least for some systems. It is not necessary to invoke a particular mechanism in the neonatal or infant period. There is increasing evidence that prematurity can be associated with long-term consequences, and this is to be anticipated from conceptual considerations. Different preventative strategies may be relevant in different populations.

Early Life Factors and Blood Pressure at Age 31 Years in the 1966 Northern Finland Birth Cohort

Data on the birth weight-blood pressure relationship are inconsistent. Although an inverse association has been suggested in several large studies, interpretation is complicated by publication and other biases. Few data are available on the relationship between other early growth measures and blood pressure. We examined the shape and size of association between determinants of fetal growth, size at birth, growth in infancy, and adult systolic and diastolic blood pressure at 31 years in the prospective northern Finnish 1966 birth cohort of 5960 participants. Birth weight, birth length, gestational age, ponderal index, and birth weight relative to gestational age showed a significant inverse association with blood pressure at age 31. Rapid growth in infancy ("change-up") was positively associated with blood pressure. Adjusted regression coefficients for birth weight indicated systolic/diastolic blood pressure lower by -1.7 (95% confidence interval [CI], -2.5, -1.0)/-0.7 (95% CI, -1.4, -0.02) mm Hg for 1 kg higher birth weight. The significant inverse association between birth weight and systolic blood pressure persisted without adjustment for adult body mass index for males. Among females, gestational age showed a stronger association with blood pressure than birth weight: gestational age higher by 7 weeks (equivalent to an average of 1 kg higher birth weight) among singletons associated with -2.9 (95% CI, -4.7, -1.1) mm Hg lower systolic blood pressure. Our results support the concept that birth weight, other birth measures, and infant growth are important determinants of blood pressure and hence cardiovascular disease risk in later life.

Developmental programming of the metabolic syndrome by maternal nutritional imbalance: how strong is the evidence from experimental models in mammals?

The incidence of the metabolic syndrome, a cluster of abnormalities focusing on insulin resistance and associated with high risk for cardiovascular disease and diabetes, is reaching epidemic proportions. Prevalent in both developed and developing countries, the metabolic syndrome has largely been attributed to altered dietary and lifestyle factors that favour the development of central obesity. However, population-based studies have suggested that predisposition to the metabolic syndrome may be acquired very early in development through inappropriate fetal or neonatal nutrition. Further evidence for developmental programming of the metabolic syndrome has now been suggested by animal studies in which the fetal environment has been manipulated through altered maternal dietary intake or modification of uterine artery blood flow. This review examines these studies and assesses whether the metabolic syndrome can be reliably induced by the interventions made. The validity of the different species, diets, feeding regimes and end-point measures used is also discussed.