The role of size at birth and postnatal catch-up growth in determining systolic blood pressure: a systematic review of the literature

Growth and living conditions in childhood and hypertension in adult life: a longitudinal study

OBJECTIVES

To examine the interplay between childhood growth and living conditions in the development of hypertension.

DESIGN

A longitudinal study of people whose growth between birth and 12 years, and social circumstances during childhood and adult life, were recorded.

SETTING

Helsinki, Finland.

PARTICIPANTS

Eight thousand seven hundred and sixty men and women born in Helsinki University Central Hospital during 1934-44, who attended child welfare clinics in the city and were still resident in Finland in 1971.

MAIN OUTCOME MEASURES

Incidence of hypertension defined by prescription of medication.

RESULTS

The 1404 children who later developed hypertension grew differently to other children. Low birthweight and shortness or thinness at birth were followed by rapid compensatory growth in weight and height, and an above-average body mass index (BMI, kg/m(2)) from the age of 8 years onwards. Some 25% of children with low birthweight but high BMI at 12 years subsequently developed hypertension, compared to 9% of those with high birthweight but low BMI. Growth had large effects on the risk of later hypertension in children living in poor social conditions, but only small effects in children in good living conditions. Living conditions in adult life did not affect the risk of hypertension.

CONCLUSIONS

Hypertension originates in slow fetal growth followed by rapid compensatory growth in childhood. This path of growth has a greater effect on the risk of disease among children who live in poor social conditions. Living conditions in adult life do not seem to be important.

Secular changes in blood pressure in childhood, adolescence and young adulthood: systematic review of trends from 1948 to 1998

One plausible reason for the decline in cardiovascular disease (CVD), and in particular stroke, in the last century is population reductions in blood pressure. Blood pressure tracks from childhood into adulthood, and early-life blood pressure is associated with increased cardiovascular risk but few studies have reported on blood pressure trends among young individuals who are free of CVD and not taking antihypertensive medication. Knowledge of such trends may improve understanding of the causes of hypertension and enhance prevention. We report that declines in blood pressure have been taking place in high-income countries in 5 to 34-year-olds of both sexes and from a range of ethnic groups for at least the last 50 years, indicating that exposures acting in early life are important determinants of blood pressure. Possible explanations for these favourable trends include improvements in early-life diet and there is also intriguing evidence suggesting that blood pressure may be programmed by sodium intake in infancy. Occurring throughout the blood pressure distribution, these trends may have made important contributions to declining CVD rates. There may therefore be scope for intervening in early life to prevent high blood pressure in adulthood, and the downward trends reported in several recent studies suggest that the prevalence of adult hypertension and cardiovascular risk will continue to decline. However, persisting high rates of CVD in the developed world, the impending CVD epidemic in developing countries, along with increasing childhood obesity, and the possibility that favourable blood pressure trends may be plateauing point to the need for enhanced measures to control blood pressure, and for further research to improve understanding of its determinants.

Birthweight, childhood growth and hypertension in adulthood

BACKGROUND

Low birthweight (BW) and childhood growth have been hypothesized to be associated with an increased risk of hypertension in later life.

METHODS

We analysed data among 13,467 women with a recalled BW from the Shanghai Women's Health Study. Cases included those with a self-reported hypertension with ('confirmed cases') or without ('possible cases') antihypertensive medication(s) use. Logistic regression was used to derive adjusted odds ratios (OR) and 95% CI.

RESULTS

Birthweight was inversely associated with the odds of early onset (at age 20-40 years) hypertension in a dose response manner (P for trend = 0.01). This association is stronger for 'confirmed' hypertension (only OR for 'confirmed' hypertension are referred to subsequently). Being heavier or taller than average at 15 years of age were both related to elevated odds of early onset hypertension. Women who had a low BW but were heavier than average at age 15 were more than four times (OR = 4.63, 95% CI: 2.40-8.94) more likely to have an early onset hypertension, and those who had a low BW and became taller at 15 years of age had an OR of 1.87 (95% CI: 1.05-3.31). A significant interaction between BW and weight at age 15 was observed (P = 0.04).

CONCLUSION

Our study suggests that low BW, particularly if accompanied by accelerated childhood growth, may increase the risk of early onset hypertension in adulthood.

The association between birth weight and capillary recruitment is independent of blood pressure and insulin sensitivity: a study in prepubertal children

OBJECTIVE

Alterations in microvascular function have been hypothesized as a possible mechanism explaining the negative association of weight at birth with blood pressure and insulin resistance in adult life. However, these variables are closely associated, so that it has been difficult to establish whether microvascular dysfunction is a cause or a consequence of increased blood pressure or insulin resistance.

DESIGN

Cohort study.

SETTING

VU University Medical Center, Amsterdam, The Netherlands.

SUBJECTS

Twenty-one prepubertal healthy children showing a wide range in birth weight.

MAIN OUTCOME MEASURES

Birth weight data were obtained from hospital records. Blood pressure was measured with an ambulatory 24-h blood pressure monitor, and insulin sensitivity was assessed with the hyperinsulinaemic euglycaemic clamp technique. Microvascular function (i.e. capillary recruitment during post-occlusive reactive hyperaemia and endothelium (in)dependent vasodilatation of the skin) was evaluated by videomicroscopy and iontophoresis of acetylcholine and sodium nitroprusside.

RESULTS

Birth weight was positively and significantly associated with capillary recruitment [slope, 22%/kg birth weight; 95% confidence interval (CI), 0.1-43; 0.05]. Birth weight was not associated with insulin sensitivity and systolic blood pressure (slope, -0.11 mg/kg per min per pmol/l; 95% CI, -2.4 to 2.2; = 0.9; and slope, 1.4 mmHg; 95% CI, -5.0 to 7.7/kg birth weight; = 0.7, respectively). The association between low birth weight and impaired capillary recruitment was not affected by adjustment for blood pressure and insulin sensitivity. Birth weight was not associated with endothelium-(in)dependent vasodilatation.

CONCLUSION

These results suggest that the association between birth weight and capillary recruitment is independent of blood pressure and insulin sensitivity. These findings are consistent with the hypothesis that an impaired capillary recruitment plays a mechanistic role in the association of birth weight with blood pressure and insulin resistance in adult life.

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.

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

BACKGROUND

The association between birthweight and subsequent blood pressure levels has been considered to provide some of the strongest, and most consistent, support for the "fetal origins" hypothesis of adult disease. It had been estimated that a 1 kg higher birthweight is typically associated with a 2-4 mm Hg lower systolic blood pressure.

METHODS

55 studies that had reported regression coefficients of systolic blood pressure on birthweight (with 48 further studies that reported only the direction of this association), and seven such studies within twin pairs, were identified. Each study was weighted according to the inverse of the variance of the regression coefficient (ie, "statistical size"), and combined using a "fixed effects" approach.

FINDINGS

Among the 55 studies that reported regression coefficients, there was a clear trend (p<0.0001) towards weaker associations in the larger studies: -1.9 mm Hg/kg in those with less than about 1000 participants; -1.5 mm Hg/kg with about 1000-3000 participants; and -0.6 mm Hg/kg with more than 3000 participants. By contrast with the inverse associations reported in 52 of these 55 studies, only 25 of the 48 studies that did not report regression coefficients found an inverse association (p<0.0001 for heterogeneity). Almost all of these regression coefficients had been adjusted for current weight (whereas few were adjusted for potential confounding factors), and removal of this adjustment in the larger studies reduced the estimated association to -0.4 mm Hg/kg. For studies within monozygotic twin pairs, the combined estimate was -0.6 mm Hg/kg with adjustment for current weight, and was also reduced without this adjustment.

INTERPRETATION

Claims of a strong inverse association between birthweight and subsequent blood pressure may chiefly reflect the impact of random error, selective emphasis of particular results, and inappropriate adjustment for current weight and for confounding factors. These findings suggest that birthweight is of little relevance to blood pressure levels in later life.

Effect of maternal feed restriction on blood pressure in the adult guinea pig

Small size at birth has been associated with increased blood pressure in adult men and women. In rats, isocaloric protein restriction reduces fetal growth and increases systolic blood pressure in adult offspring. Balanced maternal undernutrition in the rat also increases adult blood pressure, but not consistently. The aim of this study was to determine the effect of moderate balanced maternal undernutrition (85% of ad libitum intake from 4 weeks before, and throughout pregnancy) on blood pressure of adult offspring in the guinea pig, a species that is relatively mature at birth. Blood pressure was measured in chronically catheterised offspring of ad libitum fed or feed-restricted mothers, at 3 months of age (young adult). Maternal feed restriction reduced birth weight (-17%) and increased systolic blood pressure (+9%, P < 0.03) in young adult male offspring. In offspring of ad libitum fed and feed-restricted mothers, combined data showed that systolic blood pressure and mean arterial pressure correlated negatively with head width at birth (P = 0.02 and P = 0.04, respectively, n = 28). Systolic blood pressure also correlated negatively with birth weight and the ratio birth weight/birth length, but only in offspring of ad libitum fed mothers (P = 0.04 and P = 0.03, respectively, n = 22). The effect of maternal feed restriction on systolic blood pressure in male offspring was not significant when adjusted for these measures of size at birth. Thus, moderate balanced undernutrition in the guinea pig increases systolic blood pressure in young adult male offspring; however, these effects may be mediated, at least in part, through effects on fetal growth.

Size at birth and carotid atherosclerosis in later life

Several studies have shown that low birthweight is associated with a higher risk of stroke and coronary heart disease in later life. Increased atherogenesis may be one underlying mechanism, but few studies have examined this directly. We used duplex ultrasonography to assess the extra-cranial carotid arteries of 389 elderly men and women born and still living in Sheffield, UK, whose recorded birth measurements were available. Men and women who had weighed 6.5 lbs or less at birth had a higher risk of having carotid stenosis >30% than those who weighed over 7.5 lbs, but this trend was not statistically significant (OR 1.8, 95% CI 1.0-3.3). Women who had been lighter or who had a smaller head circumference at birth tended to have an increased intima-media thickness, but these relations ceased to be statistically significant after adjustment for gestational age and cardiovascular risk factors. In men, by contrast, an increased intima-media thickness was associated with having been heavier at birth (P=0.049) or having had a larger abdominal circumference at birth (P=0.040), after adjustment for gestational age and cardiovascular risk factors. These results provide little evidence that impaired fetal growth increases susceptibility to atherogenesis.

Fetal growth and systolic blood pressure in young adulthood: the Swedish Young Male Twins Study

The objective was to test the fetal origins hypothesis by examining the association between fetal growth and systolic blood pressure in a large cohort of adult male twins of known zygosity. This cohort study is based on a record linkage of routinely collected data from the Swedish Medical Birth Registry, the Swedish Military Conscription Registry and a mailed questionnaire. It comprises 886 pairs of same-sex male twins born in Sweden in 1973-79 for whom data were available on size at birth and systolic blood pressure, height and weight at age 17-19 years. Based on self-reported similarity of appearance in childhood, 384 twin pairs were classified as monozygotic (MZ), 269 as dizygotic (DZ) and 233 as of uncertain zygosity (XZ). Differences in systolic blood pressure within and between twin pairs were analysed in relation to birthweight and birthweight-for-gestational-age z-score using random effects linear models. Within twin pairs, a 1 kg difference in birthweight was associated with a difference of -1.30 mmHg in systolic blood pressure [95% confidence interval -4.15, +1.54] for MZ twins and +0.14 [-3.49, +3.76] for DZ twins; for all twins combined it was -0.21 [-2.13, +1.71]. Between twin pairs, a 1 kg difference in birthweight was associated with a difference of -2.68 mmHg in systolic blood pressure [-4.95, -0.42] for MZ twins and +0.28 [-2.35, +2.91] for DZ twins; for all twins combined -1.68 [-3.15, -0.22]. All these estimates included adjustment for age, year and conscription centre of examination, gestational age and height and weight at conscription. These results provide little support for the fetal origins hypothesis. The estimates of the within-pair effect in MZ twins and their wide confidence intervals (including zero) cannot exclude the existence of common genetic mechanisms, but are also not inconsistent with an in utero programming effect. This study highlights some methodological problems with twin studies.

Programming effects of short prenatal exposure to cortisol

Recent studies have linked fetal exposure to a suboptimal intrauterine environment with adult hypertension. The aims of this study were twofold: 1) to see whether cortisol treatment administered to the ewe for 2 days at 27 days of gestation (term approximately 150 days) resulted in high blood pressure in offspring; 2) to study the effect of the same treatment on gene expression in the brain at 130 days of gestation and in lambs at 2 months of age. Mean arterial pressure was significantly higher in the adult female and male offspring of sheep treated with cortisol than in the control group (females: 89+/-2 mmHg vs. 81+/-2; P<0.05 and males: 102+/-4 mmHg vs. 91+/-3; P<0.05). Prenatal cortisol treatment led to up-regulation of angiotensinogen, AT1, MR, and GR mRNA in the hippocampus in fetuses at 130 days of gestation but not in the animals at 2 months of age. This is the first evidence that short prenatal exposure to cortisol programmed high blood pressure in the adult female and male offspring of sheep. Altered gene expression in the hippocampus could have a significant effect on the development of the hippocampus, and on postnatal behavior.

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

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

Birth weight and renal function

Low birth weight due to premature birth or to intrauterine growth retardation adversely affects normal renal development. In the period immediately after birth, the short-term renal-related consequences of low birth weight are an increased risk of acute renal failure as well as transient imbalance of fluid and electrolyte homeostasis. Epidemiological studies show that low birth weight adults are at risk of developing chronic renal disease. There are thought to be several causes for this phenomenon. Adult low birth weight subjects have an increased incidence of hypertension and type 2 diabetes, both of which are well-established risk factors for chronic renal injury. Moreover, interference with normal kidney development, as seen in low birth weight babies, results in a lower than normal number of nephrons, which might also play a role in the renal disturbances.

Fetal, infant, and childhood growth and adult blood pressure: a longitudinal study from birth to 22 years of age

BACKGROUND

People who are small at birth tend to have higher blood pressure in later life. However, it is not clear whether it is fetal growth restriction or the accelerated postnatal growth that often follows it that leads to higher blood pressure.

METHODS AND RESULTS

We studied blood pressure in 346 British men and women aged 22 years whose size had been measured at birth and for the first 10 years of life. Their childhood growth was characterized using a conditional method that, free from the effect of regression to the mean, estimated catch-up growth. People who had been small at birth but who gained weight rapidly during early childhood (1 to 5 years) had the highest adult blood pressures. Systolic pressure increased by 1.3 mm Hg (95% CI, 0.3 to 2.3) for every standard deviation score decrease in birth weight and, independently, increased by 1.6 mm Hg (95% CI, 0.6 to 2.7) for every standard deviation score increase in early childhood weight gain. Adjustment for adult body mass index attenuated the effect of early childhood weight gain but not of birth weight. Relationships were smaller for diastolic pressure. Weight gain in the first year of life did not influence adult blood pressure.

CONCLUSIONS

Part of the risk of adult hypertension is set in fetal life. Accelerated weight gain in early childhood adds to this risk, which is partly mediated through the prediction of adult fatness. The primary prevention of hypertension may depend on strategies that promote fetal growth and reduce childhood obesity.

Effect of early glucocorticoid treatment on MR and GR in late gestation ovine kidney

BACKGROUND

The ontogeny of the renal mineralocorticoid (MR) and glucocorticoid (GR) receptors in the ovine fetus, and the effects of early exposure to synthetic or natural glucocorticoids on the expression of these genes in late gestation were examined.

METHODS

A partial cDNA sequence for the ovine MR was cloned and used to generate primers and probes to measure MR mRNA expression by real-time polymerase chain reaction (PCR). GR mRNA was also measured. Kidneys were collected from ovine fetuses at various stages of gestation (days 60 to 140), twin ovine fetuses at 130 days, from ewes treated at days 26 to 28 with either saline, dexamethasone or cortisol, and adult sheep. Ligand binding was used to determine both GR and MR protein levels in all 130-day-old fetuses and adults.

RESULTS

No significant changes in the expression of either renal MR or GR were detected throughout gestation. Cytosolic protein levels were higher in the fetal kidneys than in the adult. There was a significant increase in both fetal MR and GR mRNA expression, but not protein levels in kidneys from ewes pretreated with dexamethasone.

CONCLUSIONS

MR and GR mRNA are expressed throughout development in ovine fetal kidneys. Dexamethasone treatment resulted in increased expression of MR and GR mRNA but not protein levels. The dissociation between fetal mRNA and protein levels, relative to adult kidneys, suggests that it may be confounding to draw conclusions based on mRNA levels alone.

Tracking of systolic blood pressure during childhood: a 15-year follow-up population-based family study in eastern Finland

OBJECTIVES

To investigate the tracking of systolic arterial blood pressure (SBP) during childhood.

DESIGN AND SETTING

All children born during 1981-82 in a rural community of eastern Finland were followed at the ages of 6 months, 7 and 15 years (SBP-6m, SBP-7y, SBP-15y). One hundred and thirty-eight out of 205 children completed the full follow-up period, of which 100 (45 girls) were included in the analysis with complete data.

MAIN OUTCOME MEASURES

SBP (mmHg).

RESULTS

SBP-6m was associated with SBP-7y (r = 0.715; P < 0.001) and with SBP-15y (r = 0.238; P = 0.017) and SBP-7y was associated with SBP-15y (r = 0.348; P < 0.001). Adjustment for confounders did not change these results. Children at the highest tertile of SBP-6m had a higher probability of being at the highest tertile of SBP-7y [relative risk (RR) = 4.3; 95% confidence interval (CI), (2.4-7.6)] and SBP-15y [RR = 1.9; 95% CI, (1.1-3.3)]. Children at the highest tertile of SBP-7y had a higher probability of being at the highest tertile of SBP-15y [RR = 2.6 (1.5-4.6)]. The regression analysis showed a significant main effect on SBP-15y for birth weight (negative association), male gender, current body mass index (BMI), change of BMI between the ages of 7 years and 15 years, SBP-6m, SBP-7y and the mean SBP between the ages of 6 months and 7 years (all with positive association). Children with family history of hypertension appear to have a higher SBP during childhood; however, this association did not reach a significant level.

CONCLUSIONS

The study confirmed the tracking of SBP during childhood. Birth weight was inversely associated with SBP-15y. Family history of hypertension was not significantly associated with SBP during childhood.

No evidence for HPA reset in adult sheep with high blood pressure due to short prenatal exposure to dexamethasone

Exposure of pregnant ewes to dexamethasone, for only 2 days (term approximately 150 days) at 27 days of gestation (group D), results in adult offspring with high blood pressure. In this study, hemorrhage stress has been used to see whether in these animals the responsiveness of the hypothalamo-pituitary-adrenal (HPA) axis is altered. In addition, we studied mineralocorticoid (MR) and glucocorticoid (GR) receptor gene expression in the hippocampus and GR gene expression in the hypothalamus using real-time PCR. Calculated areas under the adrenocorticotropin, arginine vasopressin, and cortisol plasma concentration curves in response to hemorrhage were similar between the control and group D. In addition, there was no significant difference in the expression of MR and GR in the hippocampus or GR in the hypothalamus between the control and group D. Taken together, it is unlikely that reset in the HPA axis plays a major role in this particular model of "programmed" hypertension.

Associations between birth weight and antihypertensive medication in black and white medicaid recipients

The blood pressures of hypertensive patients living in the southeastern region of the United States are less responsive to several classes of antihypertensive medications. Birth weights are lower among blacks and those living in the Southeast, and evidence suggests that this developmental difference increases blood pressure. As an initial step in addressing the possibility that birth weight influences response to antihypertensive therapy, we examined the relationship between birth weight and class of antihypertensive medication among 3236 Medicaid beneficiaries in South Carolina with high blood pressure. Birth weight, obtained from birth certificates, was not related to use of either diuretics or beta blockers. However, among black women, there was an inverse association between birth weight and use of calcium channel antagonists (P=0.03), which persisted after adjustment for the number of antihypertensive medications. Among white men, low and high birth weights were associated with greater use of angiotensin converting enzyme inhibitors than in men of normal birth weight (P=0.002 for quadratic trend [U-shaped]). This association remained after adjustment for comorbid conditions, including congestive heart failure and diabetes mellitus, which were associated with birth weight and for which angiotensin converting enzyme inhibitors are recommended. The findings indicate that birth weight is associated with use of calcium channel antagonists in black women and angiotensin converting enzyme inhibitors in white men. These observations suggest that further study of the relationship between birth weight and blood pressure responses to various antihypertensive medications may help elucidate pathophysiological factors contributing to geographic and racial disparities in therapeutic efficacy.

Effects of prenatal exposure to the Dutch famine on adult disease in later life: an overview

Chronic diseases are the main public health problem in Western countries. There are indications that these diseases originate in the womb. It is thought that undernutrition of the fetus during critical periods of development would lead to adaptations in the structure and physiology of the fetal body, and thereby increase the risk of diseases in later life. The Dutch famine--though a historical disaster--provides a unique opportunity to study effects of undernutrition during gestation in humans. This thesis describes the effects of prenatal exposure to the Dutch famine on health in later life. We found indications that undernutrition during gestation affects health in later life. The effects on undernutrition, however, depend upon its timing during gestation and the organs and systems developing during that critical time window. Furthermore, our findings suggest that maternal malnutrition during gestation may permanently affect adult health without affecting the size of the baby at birth. This may imply that adaptations that enable the fetus to continue to grow may nevertheless have adverse consequences of improved nutrition of pregnant women will be underestimated if these are solely based on the size of the baby at birth. Little is known about what an adequate diet for pregnant women might be. In general, women are especially receptive to advice about diet and lifestyle before and during a pregnancy. This should be exploited to improve the health of future generations.

Fetal and early life growth and body mass index from birth to early adulthood in 1958 British cohort: longitudinal study

OBJECTIVES

To determine the influence of birth weight on body mass index at different stages of later life; whether this relation persists after accounting for potential confounding factors; and the role of indicators of fetal growth (birth weight relative to parental size) and childhood growth.

DESIGN

Longitudinal study of the 1958 British birth cohort.

SETTING

England, Scotland, and Wales.

PARTICIPANTS

All singletons born 3-9 March 1958 (10 683 participants with data available at age 33).

MAIN OUTCOME MEASURES

Body mass index at ages 7, 11, 16, 23, and 33 years.

RESULTS

The relation between birth weight and body mass index was positive and weak, becoming more J shaped with increasing age. When adjustments were made for maternal weight, there was no relation between birth weight and body mass index at age 33. Indicators of poor fetal growth based on the mother's body size were not predictive, but the risk of adult obesity was higher among participants who had grown to a greater proportion of their eventual adult height by age 7. In men only, the effect of childhood growth was strongest in those with lower birth weights and, to a lesser extent, those born to lighter mothers.

CONCLUSIONS

Maternal weight (or body mass index) largely explains the association between birth weight and adult body mass index, and it may be a more important risk factor for obesity in the child than birth weight. Birth weight and maternal weight seem to modify the effect of childhood linear growth on adult obesity in men. Intergenerational associations between the mother's and her offspring's body mass index seem to underlie the well documented association between birth weight and body mass index. Other measures of fetal growth are needed for a fuller understanding of the role of the intrauterine environment in the development of obesity.

High-meat, low-carbohydrate diet in pregnancy: relation to adult blood pressure in the offspring

To examine the hypothesis that a high-animal protein, low-carbohydrate diet in pregnancy is associated with raised blood pressure in the adult offspring, we performed a follow-up study of 626 men and women in Motherwell, Scotland, whose mothers' food intake had been recorded during pregnancy. The mothers had taken part in a dietary intervention in which they were advised to eat 1 lb (0.45 kg) of red meat per day and to avoid carbohydrate-rich foods during pregnancy. The offspring were followed up at age 27 to 30 years, and their systolic and diastolic blood pressures were measured. Women who reported greater consumption of meat and fish in the second half of pregnancy had offspring with higher systolic blood pressure in adult life (regression coefficient, 0.19 mm Hg per portion per week; 95% confidence interval, 0.04 to 0.35; P=0.02). High maternal consumption of fish, but not meat, was associated with higher diastolic blood pressure in the offspring (regression coefficient, 1.00 mm Hg per portion per week; 95% confidence interval, 0.18 to 1.82; P=0.02). These associations were independent of maternal blood pressure, body size, and smoking habits during pregnancy. Although we cannot exclude confounding by maternal saturated fat or salt intake, the findings support those of a study in Aberdeen showing higher blood pressure in men and women whose mothers had eaten a high-animal protein, low-carbohydrate diet in late pregnancy. These associations may reflect the metabolic stress imposed on the mother by an unbalanced diet in which high intakes of essential amino acids are not accompanied by the nutrients required to utilize them.

Organs/systems potentially involved in one model of programmed hypertension in sheep

1. When pregnant ewes and their fetuses are exposed to the synthetic glucocorticoid dexamethasone for 2 days early in pregnancy (days 26-28; term 145-150 days), female offspring have increased blood pressure relative to a control group. In one series, this was shown to be due to increased cardiac output, concomitant with a reset mean arterial pressure/heart rate reflex. The first group of such animals had, by the age of 7 years, left ventricular hypertrophy and reduced cardiac functional capacity. 2. The elevation in blood pressure is not maintained by any change in the peripheral renin-angiotensin system (RAS). 3. There is, however, preliminary evidence that some aspects of local RAS (particularly in the kidney and brain) could have participated in the 'programming' event. The levels of mRNA for angiotensin II receptors (AT1, AT2) and angiotensinogen are increased in the kidney of such dexamethasone-treated fetuses in late gestation (130 days), some 100 days after steroid treatment. Similar increases in AT1 mRNA in the medulla oblongata of the fetal brain and large increases of mRNA for angiotensinogen occur in the hypothalamus. 4. These findings, together with evidence from the literature, suggest that both the kidney and parts of the brain are affected by events that also 'program' high blood pressure in the offspring of animals in which the intra-uterine environment has been perturbed at some stage.

The worldwide obesity epidemic

The recent World Health Organization (WHO) agreement on the standardized classification of overweight and obese, based on body mass index (BMI), allows a comparable analysis of prevalence rates worldwide for the first time. In Asia, however, there is a demand for a more limited range for normal BMIs (i.e., 18.5 to 22.9 kg/m(2) rather than 18.5 to 24.9 kg/m(2)) because of the high prevalence of comorbidities, particularly diabetes and hypertension. In children, the International Obesity Task-Force age-, sex-, and BMI-specific cutoff points are increasingly being used. We are currently evaluating BMI data globally as part of a new millennium analysis of the Global Burden of Disease. WHO is analyzing data in terms of 20 or more principal risk factors contributing to the primary causes of disability and lost lives in the 191 countries within the WHO. The prevalence rates for overweight and obese people are different in each region, with the Middle East, Central and Eastern Europe, and North America having higher prevalence rates. In most countries, women show a greater BMI distribution with higher obesity rates than do men. Obesity is usually now associated with poverty, even in developing countries. Relatively new data suggest that abdominal obesity in adults, with its associated enhanced morbidity, occurs particularly in those who had lower birth weights and early childhood stunting. Waist measurements in nationally representative studies are scarce but will now be needed to estimate the full impact of the worldwide obesity epidemic.

Prenatal undernutrition, glucocorticoids and the programming of adult hypertension

1. A range of epidemiological studies has shown that poor intra-uterine growth is associated with an increased prevalence of cardiovascular disease, non-insulin-dependent diabetes mellitus and the Metabolic syndrome in adult life. 2. Because these associations are independent of adult lifestyle or current size, it has been postulated that a reduced intra- uterine nutrient supply perturbs fetal growth and, concomitantly, alters or programmes the structure and function of developing systems. 3. A reduced fetal nutrient supply may be a consequence of poor placental function or inadequate maternal nutrient intake. 4. It has been proposed that one outcome of either a suboptimal placental or maternal nutrient supply is exposure of the fetus to excess glucocorticoids, which act to restrict fetal growth and to programme permanent changes in the cardiovascular, endocrine and metabolic systems. 5. While a range of studies in the rat has investigated the impact of maternal undernutrition on arterial blood pressure in the offspring, there have been relatively few studies in species, such as the sheep, in which the responses of the cardiovascular and neuroendocrine systems to intra-uterine undernutrition can be measured before birth. 6. The present review summarizes recent evidence that poor placental function or inadequate maternal nutrition each results in an increased exposure of fetal sheep tissues to glucocorticoids and, in specific, changes in the regulation of fetal arterial blood pressure. 7. These studies are important in determining how the timing, type and duration of fetal nutrient restriction are each important in determining the nature of the fetal neuroendocrine and cardiovascular adaptive responses and their pathophysiological sequelae in later life.

Impaired cardiac functional reserve and left ventricular hypertrophy in adult sheep after prenatal dexamethasone exposure

We have shown that exposure of pregnant ewes to dexamethasone (11.5 mg/d for 2 days) at 27 days of gestation (term, 150 days) led to increased blood pressure and cardiac output in adult offspring. In this study, we hypothesized that dexamethasone-induced hypertension is associated with left ventricular hypertrophy and a reduced cardiac functional reserve (CO(max-0)). Six control animals (group C) and five dexamethasone-exposed animals (group D) were volume-loaded with Hemaccel until the wedge pressure was 13 mm Hg (baseline). The wedge pressure was held constant during an infusion of dobutamine at incremental doses (0.4 to 12 microgram/kg/min) while blood pressure and cardiac output were measured. The same protocol was repeated in each animal 5 days later under mild general anesthesia (1.5% isoflurane), when transthoracic echocardiography (M-mode) was obtained. Group D showed a reduced CO(max-0) in response to dobutamine during both conscious (89+/-22 versus 150+/-25 mL/kg/min in control; P<0.01) and anesthetized states (91+/-38 versus 156+/-56 mL/kg/min in control; P<0.05). Reduced CO(max-0) in group D was associated with higher left ventricular mass index compared with group C (2.6+/-0.67 versus 1.8+/-0.51 g/kg; P<0.05). In addition, group D showed a reduced cardiac contractility reserve (FS(max-0)) in response to dobutamine (21+/-22% versus 54+/-34% in group C; P<0.05). An impaired cardiac functional reserve in group D was associated with increased left ventricular type I collagen content. In conclusion, brief prenatal exposure to dexamethasone led to the development of hypertension, left ventricular hypertrophy, and reduced cardiac functional reserve in adult life.

Birth weight influences blood pressure values and variability in children and adolescents

The objective of the present study was to assess the relationships between birth weight and the values and variability of ambulatory blood pressure. Six hundred thirty healthy children (369 girls) age 4 to 18 years (mean, 9.9 years) born at term after a normotensive pregnancy were included. The subjects were divided into 5 groups according to birth weight. For each subject, a 24-hour ambulatory blood pressure monitoring was performed according to the protocol designed. Average and variability (estimated as the standard deviation) of ambulatory blood pressure and heart rate were calculated separately for 24-hour, daytime, and nighttime periods. When values were adjusted for gender, current age, weight, and height, children with the lowest birth weights had the highest ambulatory blood pressure values and variability, whereas no differences in heart rate were observed. Multiple regression analysis showed that although current weight was the strongest predictor for 24-hour systolic blood pressure (P<0.001), there was also an independent and significant inverse relationship for birth weight (P<0.002) after controlling for gender, current age, and height. Likewise, birth weight was independently and inversely correlated with 24-hour systolic blood pressure variability (P<0.03). In conclusion, children who had lower birth weights tended to have not only the highest blood pressure values but also the highest blood pressure variability, independent of the increases in ambulatory blood pressure values. Knowing that high blood pressure variability is at least partially independent of blood pressure values, the importance of this variability on further blood pressure rises and/or on vascular damage later in life needs to be assessed in future studies.

Linear catch-up growth does not increase the risk of elevated blood pressure and reduces the risk of overweight in males

OBJECTIVES

To analyse if size at birth is associated with blood pressure and body mass index (BMI) at conscription in males, and if linear catch-up growth in height modifies these associations.

DESIGN

A population-based cohort study of 276 033 single-born males aged 17-24. Information from the Swedish Birth Register was individually linked to the Swedish Conscript Register. Systolic blood pressure was standardized for final height.

RESULTS

Compared to males not being small for gestational age at birth, males being light for gestational age [<-2 standard deviation scores (SDS)] were at increased risk of high systolic blood pressure [odds ratio (OR) 1.33; 95% confidence intervals (CI) 1.20-1.46], and a short adult stature was associated with a further increased risk [OR 1.65 (CI 1.13-2.40)]. Being born short for gestational age (<-2 SDS) was associated with a slightly increased risk of high systolic blood pressure [OR 1.16 (CI 1.04-1.29)], and linear catch-up growth in height did not increase this risk. Males born short for gestational age, who also were short at conscription, had an increased risk of a high BMI [OR 1.65 (CI 1.25-2.19)].

CONCLUSIONS

Males born light for gestational age have an increased risk of high systolic blood pressure, especially if they end up with short adult stature. Being born short for gestational age is associated with a slightly increased risk of high systolic blood pressure, and catch-up growth is not associated with a further risk. Lack of catch-up growth is, among males born short for gestational age, associated with an increased risk of overweight.

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.

Hypothesis: pulse pressure and human longevity

In exploration of the association between pulse pressure and longevity in humans, 3 hypotheses are briefly discussed: the fetal origin hypothesis, antagonistic pleiotropy, and the telomere hypothesis of cellular aging. The implications of these hypotheses serve to draw a critical distinction between biologic age (aging) and chronological age and, thereby, offer an answer to a question that presently matters most in the field of hypertension: Why has it been so difficult to disentangle the genetic components of essential hypertension and to identify the variant genes responsible for elevated blood pressure in a large segment of the human population?

Fetal and childhood growth and hypertension in adult life

The association between low birth weight and raised blood pressure has been extensively replicated. Little is known about the way childhood growth modifies the effects of low birth weight. We report on the fetal and childhood growth of 1958 men and women who received treatment for hypertension and belong to a cohort of 7086 people born in Helsinki, Finland, during 1924-1933. As expected, the men and women who developed hypertension had low birth weight (P=0.002). They were also shorter in body length at birth (P=0.02). After birth they experienced accelerated growth, so that by 7 years their heights and weights were approximately average. In a simultaneous regression, both birth length and tall height had statistically significant although opposing effects on hypertension (P=0.003 for birth length and 0.009 for height at 7 years). Accelerated postnatal growth was associated with better childhood living conditions. Children who later developed both hypertension and type 2 diabetes, rather than hypertension alone, had small placental size as well as small body size at birth, and their accelerated postnatal growth continued beyond 7 years. We suggest that hypertension may originate through retarded growth in utero followed by accelerated postnatal growth as a result of good living conditions. Retarded fetal growth leads to permanently reduced cell numbers in the kidney and other tissues, and subsequent accelerated growth may lead to excessive metabolic demand on this limited cell mass.