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

Lifetime growth and blood pressure in adolescence: Hong Kong's "Children of 1997" birth cohort

OBJECTIVES

Blood pressure tracks from adolescence to adulthood and is positively associated with low birth weight and faster infant growth. Most observations are from Western populations; it is unclear whether these are biologically based or contextually specific. We examined the associations of growth with blood pressure in adolescence.

METHODS

Multivariable partial least squares regression was used to assess the associations of growth to ~11 years with blood pressure at ~11 years in 5813 term births from Hong Kong's Children of 1997 birth cohort. Growth was considered as gender- and age-specific z-scores for birth weight, BMI, and length at 3 months; change in z-scores for BMI and height at 3 to 9 months, 9 to 36 months, 3 to 7 years, and 7 to 11 years; and BMI and height at 11 years.

RESULTS

Birth weight was weakly inversely associated with systolic blood pressure in girls -0.58 mm Hg 95% confidence interval -1.05 to -0.12 (boys -0.21, -0.71 to 0.30). Childhood growth, particularly linear growth at 7 to 11 years (girls: 1.27, 0.56 to 1.98; boys 2.11, 1.39 to 2.83), as well as current height (girls: 2.40, 2.04 to 2.76, boys: 2.65, 2.29 to 3.01) and BMI (girls: 2.72, 2.35 to 3.09, boys: 2.72, 2.09 to 3.36) were associated with higher systolic blood pressure. Diastolic blood pressure was also positively associated with current size.

CONCLUSIONS

In the first study to examine simultaneously the role of pre- and postnatal growth in adolescent blood pressure, the role of late childhood growth predominated.

The relationship between birth weight and blood pressure in childhood: a population-based study

BACKGROUND

Low birth weight has been associated with increased risk of hypertension later in life. The aim of this study was to evaluate the association between birth weight and blood pressure (BP) in healthy 9- to 10-year-old Icelandic children.

METHODS

Each child underwent 4 seated BP measurements, and the BP percentile was calculated from the mean of the 4 measurements. Height and weight were measured and birth weight retrieved from the Icelandic Birth Registry. Birth measures and anthropometric data were correlated with BP and BP percentiles. Multivariable linear regression was employed to examine the association between BP and birth measures.

RESULTS

Of 857 children with complete data, 445 were female (51.9%). The mean BP was 112/64 mm Hg in males and 111/63 mm Hg in females. The mean birth weight was 3714 ± 620 g. No correlation was found between birth weight and absolute BP values. A significant negative correlation between birth weight and both systolic (r = -0.09, P = 0.005) and diastolic (r = -0.08, P = 0.014) BP percentiles was observed. Gestational age did not correlate with BP.

CONCLUSION

In contrast to many previous studies, we found no association between birth weight and absolute BP in children. However, we observed a statistically significant negative correlation between birth weight and BP percentiles. The lack of standardized BP values may partly explain the conflicting results of previous studies in children, and we suggest that BP percentiles be examined more thoroughly in association with birth weight.

The impact of childhood obesity on morbidity and mortality in adulthood: a systematic review

The objective of this study was to evaluate the evidence on whether childhood obesity is a risk factor for adult disease, independent of adult body mass index (BMI). Ovid MEDLINE (1948-May 2011), EMBASE (1980-2011 week 18) and the Cochrane Library (1990-2011) were searched for published studies of BMI from directly measured weight and height in childhood (2-19 years) and disease outcomes in adulthood. Data were synthesized in a narrative fashion. Thirty-nine studies (n 181-1.1 million) were included in the review. There was evidence for associations between childhood BMI and type 2 diabetes, hypertension and coronary heart disease. Few studies examined associations independent of adult BMI; these showed that effect sizes were attenuated after adjustment for adult BMI in standard regression analyses. Although there is a consistent body of evidence for associations between childhood BMI and cardiovascular outcomes, there is a lack of evidence for effects independent of adult BMI. Studies have attempted to examine independent effects using standard adjustment for adult BMI, which is subject to over-adjustment and problems with interpretation. Studies that use more robust designs and analytical techniques are needed to establish whether childhood obesity is an independent risk factor for adult disease.

Birth weight and long-term overweight risk: systematic review and a meta-analysis including 643,902 persons from 66 studies and 26 countries globally

BACKGROUND

Overweight is among the major challenging health risk factors. It has been claimed that birth weight, being a critical indicator of prenatal developmental conditions, is related to long-term overweight risk. In order to check this important assumption of developmental and preventive medicine, we performed a systematic review and comprehensive meta-analysis.

METHODS AND FINDINGS

Relevant studies published up to January 2011 that investigated the relation between birth weight and later risk of overweight were identified through literature searches using MEDLINE and EMBASE. For meta-analysis, 66 studies from 26 countries and five continents were identified to be eligible, including 643,902 persons aged 1 to 75 years. We constructed random-effects and fixed-effects models, performed subgroup-analyses, influence-analyses, assessed heterogeneity and publication bias, performed meta-regression analysis as well as analysis of confounder adjusted data. Meta-regression revealed a linear positive relationship between birth weight and later overweight risk (p<0.001). Low birth weight (<2,500 g) was found to be followed by a decreased risk of overweight (odds ratio (OR) =0.67; 95% confidence interval (CI) 0.59-0.76). High birth weight (>4,000 g) was associated with increased risk of overweight (OR=1.66; 95% CI 1.55-1.77). Results did not change significantly by using normal birth weight (2,500-4,000 g) as reference category (OR=0.73, 95% CI 0.63-0.84, and OR=1.60, 95% CI 1.45-1.77, respectively). Subgroup- and influence-analyses revealed no indication for bias/confounding. Adjusted estimates indicate a doubling of long-term overweight risk in high as compared to normal birth weight subjects (OR=1.96, 95% CI 1.43-2.67).

CONCLUSIONS

Findings demonstrate that low birth weight is followed by a decreased long-term risk of overweight, while high birth weight predisposes for later overweight. Preventing in-utero overnutrition, e.g., by avoiding maternal overnutrition, overweight and/or diabetes during pregnancy, might therefore be a promising strategy of genuine overweight prevention, globally.

Low birth weight is associated with higher blood pressure variability from childhood to young adulthood: the Bogalusa Heart Study

The association between birth weight and long-term within-individual variability of blood pressure (BP) was examined in a longitudinal cohort of 1,454 adults (939 whites and 515 blacks; adulthood age = 19-50 years) enrolled in the Bogalusa Heart Study in Bogalusa, Louisiana, in 1973-2010. BP variability was depicted as standard deviation, coefficient of variation, and deviation from age-predicted values using 6-15 serial BP measurements from childhood to adulthood over an average of 25.7 years. Birth weight was significantly and negatively associated with adulthood BP levels, long-term BP levels, and rate of change. Importantly, low birth weight was significantly associated with increased BP variability in terms of standard deviation, coefficient of variation, and deviation. As evaluated using the regression coefficients, a 1-kg lower birth weight was associated with increases in systolic BP variability measures (-0.38 mm Hg, P = 0.04 for standard deviation; -0.004 mm Hg, P = 0.01 for coefficient of variation; and -0.16 mm Hg, P = 0.04 for deviation) after adjustment for race, age, sex, mean BP levels, and gestational age; similar trends in the associations were noted for diastolic BP variability measures. In conclusion, these findings suggest that birth weight affects not only BP levels but also the magnitude of within-individual BP fluctuations over time through fetal programming in BP regulation mechanisms.

Early postnatal life as a critical time window for determination of long-term metabolic health

Epidemiological studies demonstrated a clear phenomenological association between low birth weight and increased cardiometabolic risk later in life, very similar to that in high birth weight subjects. Pre- and/or neonatal overfeeding appears to be an etiological clue. In animal studies, irrespective of birth weight neonatal over-nutrition leads to later overweight, impaired glucose tolerance and cardiometabolic alterations. Probably, perinatally acquired alterations of DNA methylation patterns of gene promoters of central nervous regulators of body weight and metabolism play a key role in mediating these relationships. In humans, the long-term impact of neonatal nutrition is conclusively demonstrated by studies on the consequences of breastfeeding vs. formula-feeding. Taken together, the quantity and quality of nutrition during neonatal life plays a critical role, beyond prenatal development, in the long-term programming of health and disease. This opens a variety of opportunities and challenges to primarily prevent chronic diseases, e.g. the metabolic syndrome.

Role of birth weight and postnatal growth on pulse wave velocity in teenagers

PURPOSE

Low birth weight and accelerated postnatal growth appear to play a significant role in the pathogenesis of hypertension and cardiovascular disease in adulthood. The aim of the present study was to characterize the factors determining pulse wave velocity (PWV) in teenagers and, in particular, to verify the relationship with birth weight, postnatal growth, timing of adiposity rebound, lifestyle, and hemodynamic parameters.

METHODS

Carotid-femoral and carotid-radial pulse wave velocities of 558 healthy teenagers (age range: 16.2-19.9 years) were determined by means of a PulsePen tonometer. Birth weight and gestational age were obtained from obstetrical records, and data regarding postnatal growth were obtained from pediatric clinical records.

RESULTS

No change in aortic PWV was found in association with birth weight, postnatal growth, and timing of adiposity rebound. However, the study showed a strong association between accelerated growth from 0 to 12 months and carotid-radial PWV (trend: p = .02). Subjects with birth weight values <2,500 g showed higher values of upper limb PWV (p < .05) and higher values of diastolic and mean arterial pressure (p < .05). Stepwise regression analysis revealed that mean arterial pressure, age, and height were the main independent factors determining aortic PWV in this young population.

CONCLUSIONS

These results suggest that there is no linear correlation between birth weight and hemodynamic parameters in teenagers; however, subjects characterized by very low birth weight and accelerated postnatal weight gain appear to demonstrate increased upper limb PWV and diastolic and mean arterial pressure values.

Validity of maternal birthweight recall among Colombian children

Low birthweight and preterm birth are associated with adverse health outcomes later in life, but acquisition of accurate birthweight information is not always feasible in large epidemiological studies. We examined the validity of child birthweight and gestational age recall by mothers, and the extent to which recall bias affects associations between birthweight and childhood obesity in children from Bogotá, Colombia. We surveyed mothers of 3,202 schoolchildren aged 5-12 years about child's weight and gestational age at birth, and sociodemographic characteristics. In a subsample of 279 children, we obtained hospital birth records and extracted birthweight, gestational age, and other perinatal information. Mean birthweight (SD) was 3,106 (739) grams according to maternal recall and 2,977 (462) grams according to hospital records (difference 129 g; 95% CI = 55, 203). Thirty-three percent of mothers recalled their children's birthweights exactly as they appeared in hospital records. Mother's age and fewer years of education were each significantly associated with greater birthweight recall bias. Specificity of low birthweight (<2,500 g) and preterm birth (<37 weeks gestation) from maternal recall was 0.95 and 0.86, respectively; however, sensitivity was lower (0.66 and 0.67, respectively). Associations between recalled birthweight and BMI-for-age or overweight during school age were weaker than those with hospital record birthweight. Maternal birthweight recall 5-12 years after birth differs from hospital record birthweight by a clinically meaningful amount. Birthweight recall should be used with caution in epidemiological studies conducted in this and comparable settings. Associations between birthweight and obesity may be stronger than they appear when using recalled birthweight.

The fetal origins of adult disease: a narrative review of the epidemiological literature

The fetal origins of adult disease (FOAD) hypothesis suggests that risk factors from intrauterine environmental exposures affect the fetus' development during sensitive periods, and increases the risk of specific diseases in adult life. This link was initially observed between prenatal exposures and adult coronary heart disease, but corresponding observations have later been published for a range of chronic conditions. Although the hypothesis has been praised as an essential shift in our understanding of determinants for health, the hypothesis has also been criticized on a number of accounts, both methodologically and theoretically. The aim of this paper is to critically discuss the FOAD-hypothesis, in relation to the epidemiological evidence. We conclude that much of the research literature on the FOAD-hypothesis finds support for the hypothesis. Despite this, it is still unclear if the effects are independent and what the public health relevance is. Notwithstanding the heart of the hypothesis – that environmental influences during gestation have an effect on later development – should be considered a major insight and constitutes a complement to a focus on genetic and more proximal factors (such as adult lifestyle) as causes of adult disease. As the search for determinants for disease and health continues, the FOAD-hypothesis is likely to remain an important perspective. It may however be better positioned as part of a broader life course perspective, rather than as an independent hypothesis.

The association between prenatal psychosocial stress and blood pressure in the child at age 5-7 years

Objective

Prenatal maternal stress could have permanent effects on the offspring’s tissue structure and function, which may predispose to cardiovascular diseases. We investigated whether maternal psychosocial stress is a prenatal factor affecting the blood pressure (BP) of offspring.

Study Design

In the Amsterdam Born Children and their Development (ABCD) study, around gestational week 16, depressive symptoms, state-anxiety, pregnancy-related anxiety, parenting daily hassles and job strain were recorded by questionnaire. A cumulative stress score was also calculated (based on 80^th percentiles). Systolic and diastolic BP and mean arterial pressure (MAP) were measured in the offspring at age 5–7 years. Inclusion criteria were: no use of antihypertensive medication during pregnancy; singleton birth; no reported cardiovascular problems in the child (N = 2968 included).

Results

After adjustment for confounders, the single stress scales were not associated with systolic and diastolic BP, MAP and hypertension (p>0.05). The presence of 3–4 psychosocial stressors prenatally (4%) was associated with 1.5 mmHg higher systolic and diastolic BP (p = 0.046; p = 0.04) and 1.5 mmHg higher MAP in the offspring (p = 0.02) compared to no stressors (46%). The presence of 3–4 stressors did not significantly increase the risk for hypertension (OR 1.8; 95% CI 0.93.4). Associations did not differ between sexes. Bonferroni correction for multiple testing rendered all associations non-significant.

Conclusions

The presence of multiple psychosocial stressors during pregnancy was associated with higher systolic and diastolic BP and MAP in the child at age 5–7. Further investigation of maternal prenatal stress may be valuable for later life cardiovascular health.

Does an early childhood intervention affect cardiometabolic risk in adulthood? Evidence from a longitudinal study of preschool attendance in South Australia

OBJECTIVES

There is an expectation that a positive social, cognitive and behavioural trajectory from early childhood developmental interventions will lead to improved population health and reduced health inequalities. However, there is limited direct evidence for this. The aim of this study was to assess the effect of participation in the South Australian Kindergarten Union preschool programme on adult cardiovascular biomedical risk factors. Kindergarten Union preschools delivered high-quality, comprehensive services to children aged 2-4 years and their families, including education, parenting and health services.

STUDY DESIGN

Retrospective population-based cohort study.

METHODS

The effect of attendance at a Kindergarten Union preschool on a range of cardiometabolic risk factors was assessed using data from the North West Adelaide Health Study 1999-2007. The study sample was taken from participants in the 2007 survey (n = 1064, 44.8% attended preschool) who lived in South Australia as children and were born during the years 1937-1969.

RESULTS

Preschool attendance had a beneficial effect on hypertension in adulthood [prevalence ratio 0.82, 95% confidence interval (CI) 0.69-0.97] and an indication of benefit on hypercholesterolaemia (prevalence ratio 0.86, 95% CI 0.71-1.05), but had no effect on dyslipidaemia, central obesity, high fasting blood glucose or metabolic syndrome.

CONCLUSIONS

This study found that preschool attendance was associated with reduced risk of hypertension in adulthood, but no effect was seen for the other cardiometabolic factors. These findings may reflect differing causal pathways and trajectories of these risk factors from childhood to adulthood, but confirmation from other studies is required.

Population heterogeneity in trajectories of midlife blood pressure

BACKGROUND

We investigated whether there are subgroups with different underlying (latent) trajectories of midlife systolic blood pressure (BP), diastolic BP, and pulse pressure in a UK cohort.

METHODS

Data are from 1840 men and 1819 women with BP measured at ages 36, 43, and 53 years. We used unconditional growth mixture models to test for the presence of latent trajectory classes. Extracted classes were described in terms of a number of known lifetime risk factors, and linked to the risk of undiagnosed angina (Rose questionnaire) at age 53 years.

RESULTS

In both sexes for systolic BP, diastolic BP, and pulse pressure, there was a large "normative" class (>90% of the sample) characterized by gentle annual increases (eg, an increase in male systolic BP of 0.9 mm Hg/year [95% confidence interval = 0.9 to 1.0]), with a smaller class for whom the rate of increase was high (eg, an increase in male systolic BP of 3.1 mm Hg/year [2.8 to 3.4]). In women, there was an additional class for whom BP was high at age 36 and remained high. Persons in the "normative" classes were, on average, heavier at birth and taller at age 7 years, had a lower midlife body mass index, and were less likely to be on antihypertensive medication compared with those in other classes. Among those with no diagnosed cardiovascular disease, those in the classes with more strongly increasing systolic BP and pulse pressure were at greatest risk of angina.

CONCLUSION

Our study suggests that in midlife the majority of the population have a gentle underlying increase in BP, but that there also exists an important subgroup in whom BP increases much more markedly. These classes may be useful for identifying those most at risk for cardiovascular disease.

Excess early postnatal weight gain leads to increased abdominal fat in young children

Background. Increased childhood weight gain has been associated with later adiposity. Whether excess early postnatal weight gain plays a role in childhood abdominal fat is unknown. Design. In the ongoing Wheezing Illnesses Study Leidsche Rijn (WHISTLER), birth cohort weight and length from birth to age 3 months were obtained. In the first 316 five-year-olds, intra-abdominal and subcutaneous fat were measured ultrasonographically. Individual weight and length gain rates were assessed in each child. Internal Z-scores of weight for length gain (WLG) were calculated. Multiple imputation was used to deal with missing covariates. Results. Per-1-unit increase in Z-score WLG from birth to 3 months, BMI, waist circumference, and subcutaneous fat were significantly higher; 0.51 kg/m(2), 0.84 cm, and 0.50 mm, respectively. After multiple imputation, a trend towards significance was observed for intra-abdominal fat as well (0.51 mm/SD). In the associations with 5-year adiposity, no interaction between postnatal Z-score WLG and birth size was found. Conclusion. Excess early postnatal weight gain is associated with increased general and central adiposity, characterized by more subcutaneous and likely more intra-abdominal fat at 5 years of age.

Differences in association between birth parameters and blood pressure in children from preschool to high school

We aimed to investigate the association between birth parameters with blood pressure (BP) among preschool- and school-aged children. Two separate childhood datasets were used: (1) 1295 children aged 3-6 years were examined during 2007-2009; and (2) 1741 and 2353 children aged 6 and 12 years, respectively, were examined during 2004-2006. Birth parameter data were obtained from parental records. BP was measured using standard protocols. Among 6-year-old children, each 1 kg decrease in birth weight was associated with a 1.33- and 1.20-mm Hg higher systolic and diastolic BP, respectively, after multivariable adjustment. In 6-year-old children, a decrease of 1 week in gestational age was independently associated with a 0.33- and 0.37-mm Hg higher systolic and diastolic BP, respectively. Six-year-old children in the low birth weight category (≤ 2499 g) versus those in the normal/high birth weight category (≥ 2500 g) had significantly higher systolic BP (P<0.0001). Girls in the low birth weight category versus those in the normal/high weight category had higher systolic BP (P=0.02). Significant associations were not observed among preschool-aged children and preadolescents. Birth weight and gestational age were strongly associated with BP among 6-year-old children, particularly girls, but not among preschoolers or preadolescents.

Is low birth weight associated with adiposity in contemporary U.S. youth? The Exploring Perinatal Outcomes among Children (EPOCH) Study

Little is known about the relationship between low birth weight (BW), as a marker of under-nutrition in utero, and childhood body mass index (BMI) and adiposity parameters, including skinfold thickness, abdominal subcutaneous (SAT) and visceral adipose tissues (VAT) and intramyocellular accumulation of lipids (IMCL). The EPOCH Study (Exploring Perinatal Outcomes among Children) explored the association between BW and markers of adiposity in contemporary, multi-ethnic children from Colorado. A total of 442 youth age 6-13 years (50% male, mean age 10.5 years) had anthropometric measurements, abdominal SAT and VAT measured by magnetic resonance imaging and IMCL deposition in the soleus muscle measured by nuclear magnetic resonance spectroscopy. BW and gestational age were ascertained from an electronic perinatal database. A weak positive association between BW and current BMI (P=0.05) was seen, independent of demographic, perinatal, socio-economic and current lifestyle factors. When adjusted for current BMI, every one standard deviation decrease in BW (~500 g), was associated with a 8.8 cm(2) increase in SAT, independent of potential confounders. In conclusion, in a contemporary cohort of youth, BW was positively, but weakly, associated with BMI and inversely, though weakly, associated with SAT, independent of current BMI. There were no significant associations between BW and waist circumference, skinfolds, VAT and IMCL. Our results provide some support to the hypothesis that under-nutrition in utero, as reflected by lower BW, is associated with lower overall childhood body size, but an increased propensity for abdominal adiposity, reflected in this young age-group, predominantly as subcutaneous fat.

How the Newcastle Thousand Families birth cohort study has contributed to the understanding of the impact of birth weight and early life socioeconomic position on disease in later life

Much has been made of the potential influence of birth weight and early socioeconomic disadvantage in influencing adult health, but little has been published in terms of how important these associations may be with respect to exposures throughout the lifecourse. The objective of this review is to describe the contributions of the Newcastle Thousand Families Study in understanding the relative impacts of factors in early life, particularly birth weight and socio-economic position at birth, in influencing health in later life. The Newcastle Thousand Families Study is a prospective birth cohort established in 1947. It originally included all births to mothers resident in Newcastle upon Tyne, in northern England, in May and June of that year. Study members were followed extensively throughout childhood and intermittently in adulthood. At the age of 49-51 years, study members underwent a large-scale follow-up phase enabling an assessment of how early life may influence their later health, and also incorporating adult risk factors which enabled the relative contributions of factors at different stages of life to be assessed. While some findings from the study do support birth weight and early socio-economic position having influences on adult health status, the associations are generally small when compared to risk factors later in life. Using path analyses on longitudinal data of this nature enables mediating pathways between early life and later health to be assessed and if more studies were to take this approach, the relative importance of early life on adult disease risk could be better understood.

Birth weight and subsequent blood pressure: a meta-analysis

Hypertension is becoming an important health problem in many countries. The 'small baby syndrome hypothesis' suggests that an inverse linear relationship exists between birth weight and later risk of hypertension; however, this relationship is under debate. We conducted a meta-analysis to examine the association between birth weight and subsequent blood pressure. Among 78 studies reporting on the association between birth weight and subsequent blood pressure, 20 articles (reporting 27 original studies) were eligible for inclusion. Low birth weight (< 2500 g) compared with birth weight greater than 2500 g was associated with an increased risk of hypertension (odds ratio [OR] 1.21; 95% confidence interval [CI] 1.13, 1.30); high birth weight (> 4000 g) compared with birth weight less than 4000 g was associated with a decreased risk of hypertension (OR 0.78; 95% CI 0.71, 0.86). When low birth weight (< 2500 g) was compared with birth weight greater than 2500 g, mean systolic blood pressure (SBP) increased by 2.28 mmHg (95% CI 1.24, 3.33); when high birth weight (> 4000 g) was compared with birth weight less than 4000 g, mean SBP decreased by 2.08 mmHg (95% CI -2.98, -1.17). These findings indicate that there is an inverse linear association between birth weight and later risk of hypertension, and that this association primarily exists between birth weight and SBP.

Analysis of baseline parameters in the HALT polycystic kidney disease trials

HALT PKD consists of two ongoing randomized trials with the largest cohort of systematically studied patients with autosomal dominant polycystic kidney disease to date. Study A will compare combined treatment with an angiotensin-converting inhibitor and receptor blocker to inhibitor alone and standard compared with low blood pressure targets in 558 early-stage disease patients with an eGFR over 60 ml/min per 1.73 m(2). Study B will compare inhibitor-blocker treatment to the inhibitor alone in 486 late-stage patients with eGFR 25-60 ml/min per 1.73 m(2). We used correlation and multiple regression cross-sectional analyses to determine associations of baseline parameters with total kidney, liver, or liver cyst volumes measured by MRI in Study A and eGFR in both studies. Lower eGFR and higher natural log-transformed urine albumin excretion were independently associated with a larger natural log-transformed total kidney volume adjusted for height (ln(HtTKV)). Higher body surface area was independently associated with a higher ln(HtTKV) and lower eGFR. Men had larger height-adjusted total kidney volume and smaller liver cyst volumes than women. A weak correlation was found between the ln(HtTKV) and natural log-transformed total liver volume adjusted for height or natural log liver cyst volume in women only. Women had higher urine aldosterone excretion and lower plasma potassium. Thus, our analysis (1) confirms a strong association between renal volume and functional parameters, (2) shows that gender and other factors differentially affect the development of polycystic disease in the kidney and liver, and (3) suggests an association between anthropomorphic measures reflecting prenatal and/or postnatal growth and disease severity.

Drawing causal inferences in epidemiologic studies of early life influences

Observational studies can describe associations between early life exposures and subsequent outcomes in human populations. It is challenging to draw causal inferences from these associations because exposures often occur many years before the outcome and are related to other early life exposures. An approach is required that combines traditional epidemiologic and statistical principles with the use of novel and sophisticated analytic methods. To minimize the bias in longitudinal studies of early origins, researchers need to do all they can to reduce losses to follow-up and to describe individuals who are lost to follow-up. To reduce the role of chance, researchers should concentrate on effect sizes and the strength of the evidence to support these effect sizes, and they should be cautious in their interpretation of subgroup analyses. More complex analytic approaches can and should be used to handle missing data and repeated measurements. Addressing the issue of confounding is not straightforward. Statistical adjustment for the confounders measured in a study may help, but a lack of attenuation does not guarantee that the association is not confounded. Ecologic studies, observational studies in populations with different confounding structures, and the follow-up of randomized trials (where these exist) can be informative. Genetic and nongenetic instrumental variable approaches (eg, Mendelian randomization) may also provide causal insights. These approaches to confounding often require the comparison of data from different populations or a combination of studies to ensure adequate power to provide robust estimates of the causal effect.

Associations of growth trajectories in infancy and early childhood with later childhood outcomes

BACKGROUND

Weight and length at birth (which represent fetal growth) and weight and length or height gain during childhood (which potentially represent catch-up growth) may be related to later health outcomes. However, methods for the assessment of such relations are complex and underdeveloped.

OBJECTIVES

We aimed to describe childhood weight and length or height trajectories and to relate these to later outcomes by using rash at age 6.5 y as an example.

DESIGN

The data came from a prospective cohort study in Belarus in 10,494 children born in 31 hospitals that participated in a cluster randomized trial of breastfeeding promotion. Weight and length or height were measured at birth, at scheduled clinic visits up to 1 y, and at 6.5 y; intermediate measures were obtained from routine child health records. Linear spline multilevel models for weight and length or height were used to estimate each child's deviance from average birth weight, birth length, weight, and length or height gain velocity in each time period. Logistic regression was used to relate the outcome (parental report of rash at 6.5 y) to these weight and length or height estimates.

RESULTS

The best-fitting splines for length or height and weight had knots at 3 and 12 mo, with another knot at 34 mo for height. The only relation between weight and length or height and reported rash was a positive association with weight gain velocity between 12 and 34 mo (odds ratio per SD increase in weight gain velocity: 1.11; 95% CI: 1.01, 1.22).

CONCLUSION

Advantages of multilevel models include no restriction to measures at arbitrary times or to individuals with complete data and allowance for measurement error. This trial was registered at isrctn.org as ISRCTN37687716.

Protein-energy malnutrition during early gestation in sheep blunts fetal renal vascular and nephron development and compromises adult renal function

Non-technical summary

A poor diet during pregnancy has been linked to long-term health outcomes for the baby, such as an increased risk of diseases of the heart and kidney. We show in an experimental model that recreates a poor diet during pregnancy, i.e. a diet low in protein with adequate energy, that kidney development in the baby is affected in such a way as to reduce the potential for new blood vessels to form. This results in a greater number of important, functional kidney cells spontaneously dying. Later in life, these effects in the kidney manifest as permanently reduced kidney function, especially if the baby subsequently becomes overweight as an adult. The research reinforces advice to pregnant mothers about the importance of eating a nutritionally balanced diet during pregnancy.

Abstract

A nutritionally poor maternal diet can reduce nephron endowment and pre-empt premature expression of markers for chronic renal disease in the offspring. A mechanistic pathway from variation in maternal diet through altered fetal renal development to compromised adult kidney structure and function with adult-onset obesity has not been described. We show that maternal protein-energy malnutrition in sheep blunts nephrogenic potential in the 0.44 gestation (65 days gestation, term ∼147 days) fetus by increasing apoptosis and decreasing angiogenesis in the nephrogenic zone, effects that were more marked in male fetuses. As adults, the low-protein-exposed sheep had reduced glomerular number and microvascular rarefaction in their kidneys compensated for, respectively, by glomerular hypertrophy and increased angiogenic support. In this study, the long-term mild anatomical deficits in the kidney would have remained asymptomatic in the lean state, but when superimposed on the broad metabolic challenge that obesity represents then microalbuminuria and blunted bilateral renal function revealed a long-term physiological compromise, that is only predicted to worsen with age. In conclusion, maternal protein-energy malnutrition specifically impacts fetal kidney vascular development and prevents full functionality of the adult kidney being achieved; these residual deficits are predicted to significantly increase the expected incidence of chronic kidney disease in prenatally undernourished individuals especially when coupled with a Western obesogenic environment.

Early-life origins of adult disease: national longitudinal population-based study of the United States

OBJECTIVES

We examined the relation between low birth weight and childhood family and neighborhood socioeconomic disadvantage and disease onset in adulthood.

METHODS

Using US nationally representative longitudinal data, we estimated hazard models of the onset of asthma, hypertension, diabetes, and stroke, heart attack, or heart disease. The sample contained 4387 children who were members of the Panel Study of Income Dynamics in 1968; they were followed up to 2007, when they were aged 39 to 56 years. Our research design included sibling comparisons of disease onset among siblings with different birth weights.

RESULTS

The odds ratios of having asthma, hypertension, diabetes, and stroke, heart attack, or heart disease by age 50 years for low-birth weight babies vs others were 1.64 (P < .01), 1.51 (P < .01), 2.09 (P < .01), and 2.16 (P < .01), respectively. Adult disease prevalence differed substantially by childhood socioeconomic status (SES). After accounting for childhood socioeconomic factors, we found a substantial hazard ratio of disease onset associated with low birth weight, which persisted for sibling comparisons.

CONCLUSIONS

Childhood SES is strongly associated with the onset of chronic disease in adulthood. Low birth weight plays an important role in disease onset; this relation persists after an array of childhood socioeconomic factors is accounted for.

Cardiovascular and metabolic influences of fetal smoke exposure

Many epidemiological studies showed associations of low birth weight with cardiovascular disease, type 2 diabetes and obesity. The associations seem to be consistent and stronger among subjects with a postnatal catch up growth. It has been suggested that developmental changes in response to adverse fetal exposures might lead to changes in the fetal anatomy and physiology. These adaptations may be beneficial for short term, but may lead to common diseases in adulthood. Maternal smoking during pregnancy is one of the most important adverse fetal exposures in Western countries, and is known to be associated with a 150-200 g lower birth weight. An accumulating body of evidence suggests that maternal smoking during pregnancy might be involved in pathways leading to both low birth weight and common diseases, including cardiovascular disease, type 2 diabetes and obesity, in adulthood. In this review, we discuss epidemiological studies focused on the associations of maternal smoking with fetal growth and development and cardiovascular and metabolic disease in later life. We also discuss potential biological mechanisms, and challenges for future epidemiological studies.

Cardiovascular and metabolic influences of fetal smoke exposure

Many epidemiological studies showed associations of low birth weight with cardiovascular disease, type 2 diabetes and obesity. The associations seem to be consistent and stronger among subjects with a postnatal catch up growth. It has been suggested that developmental changes in response to adverse fetal exposures might lead to changes in the fetal anatomy and physiology. These adaptations may be beneficial for short term, but may lead to common diseases in adulthood. Maternal smoking during pregnancy is one of the most important adverse fetal exposures in Western countries, and is known to be associated with a 150–200 g lower birth weight. An accumulating body of evidence suggests that maternal smoking during pregnancy might be involved in pathways leading to both low birth weight and common diseases, including cardiovascular disease, type 2 diabetes and obesity, in adulthood. In this review, we discuss epidemiological studies focused on the associations of maternal smoking with fetal growth and development and cardiovascular and metabolic disease in later life. We also discuss potential biological mechanisms, and challenges for future epidemiological studies.

Low nephron number and its clinical consequences

Epidemiologic studies now strongly support the hypothesis, proposed over two decades ago, that developmental programming of the kidney impacts an individual's risk for hypertension and renal disease in later life. Low birth weight is the strongest current clinical surrogate marker for an adverse intrauterine environment and, based on animal and human studies, is associated with a low nephron number. Other clinical correlates of low nephron number include female gender, short adult stature, small kidney size, and prematurity. Low nephron number in Caucasian and Australian Aboriginal subjects has been shown to be associated with higher blood pressures, and, conversely, hypertension is less prevalent in individuals with higher nephron numbers. In addition to nephron number, other programmed factors associated with the increased risk of hypertension include salt sensitivity, altered expression of renal sodium transporters, altered vascular reactivity, and sympathetic nervous system overactivity. Glomerular volume is universally found to vary inversely with nephron number, suggesting a degree of compensatory hypertrophy and hyperfunction in the setting of a low nephron number. This adaptation may become overwhelmed in the setting of superimposed renal insults, e.g. diabetes mellitus or rapid catch-up growth, leading to the vicious cycle of on-going hyperfiltration, proteinuria, nephron loss and progressive renal functional decline. Many millions of babies are born with low birth weight every year, and hypertension and renal disease prevalences are increasing around the globe. At present, little can be done clinically to augment nephron number; therefore adequate prenatal care and careful postnatal nutrition are crucial to optimize an individual's nephron number during development and potentially to stem the tide of the growing cardiovascular and renal disease epidemics worldwide.

The relatively small contribution of birth weight to blood pressure at age 49-51 years in the Newcastle Thousand Families Study

BACKGROUND

Whereas a large number of previous studies suggest an association between birth weight and later blood pressure, others do not. Controversy surrounds the relative importance of these associations, in particular in relation to more modifiable factors in later life. The aim of this study was to investigate the relative contributions of a range of factors from across life to variations in SBP and DBP in the Newcastle Thousand Families Study.

METHODS AND RESULTS

Detailed information was collected prospectively during childhood, including birth weight, duration breast fed and socioeconomic conditions. At age 49-51 years, 574 study members returned self-completion questionnaires and 412 underwent clinical examination, including measurement of DBP and SBP. These data were analysed using linear regression and path analyses. After adjustment for all other significant variables, decreased birth weight, standardized for sex and gestational age (P = 0.035), increased BMI (P < 0.001) and being male (P = 0.034) were independently associated with raised SBP and DBP. Social class at birth (P = 0.044) was also independently associated with DBP. BMI was found to be the most important predictor, with a small relative contribution of standardized birth weight.

CONCLUSION

Adult blood pressure is influenced by numerous factors, acting both directly and indirectly during an individual's lifetime. Inverse associations of standardized birth weight, although statistically significant, were of relatively small importance, with the majority of variation being explained by more modifiable factors in adulthood, in particular adult BMI.

Fetal programming and metabolic syndrome

Metabolic syndrome is reaching epidemic proportions, particularly in developing countries. In this review, we explore the concept-based on the developmental-origin-of-health-and-disease hypothesis-that reprogramming during critical times of fetal life can lead to metabolic syndrome in adulthood. Specifically, we summarize the epidemiological evidence linking prenatal stress, manifested by low birth weight, to metabolic syndrome and its individual components. We also review animal studies that suggest potential mechanisms for the long-term effects of fetal reprogramming, including the cellular response to stress and both organ- and hormone-specific alterations induced by stress. Although metabolic syndrome in adulthood is undoubtedly caused by multiple factors, including modifiable behavior, fetal life may provide a critical window in which individuals are predisposed to metabolic syndrome later in life.

Is infant weight associated with childhood blood pressure? Analysis of the Promotion of Breastfeeding Intervention Trial (PROBIT) cohort

BACKGROUND

Weight gain during infancy may programme later health outcomes, but examination of this hypothesis requires appropriate lifecourse methods and detailed weight gain measures during childhood. We examined associations between weight gain in infancy and early childhood and blood pressure at the age of 6.5 years in healthy children born at term.

METHODS

We carried out an observational analysis of data from a cluster-randomized breastfeeding promotion trial in Belarus. Of 17 046 infants enrolled between June 1996 and December 1997, 13 889 (81.5%) had systolic and diastolic blood pressure measured at 6.5 years; 10 495 children with complete data were analysed. A random-effects linear spline model with three knot points was used to estimate each individual's birthweight and weight gain from birth to 3 months, 3 months to 1 year and 1-5 years. Path analysis was used to separate direct effects from those mediated through subsequent weight gain.

RESULTS

In boys, after controlling for confounders and prior weight gain, the change in systolic blood pressure per z-score increase in weight gain was 0.09 mmHg [95% confidence interval (95% CI) -0.14 to 0.31] for birthweight; 0.41 mmHg (95% CI 0.19-0.64) for birth to 3 months; 0.69 mmHg (95% CI 0.47-0.92) for 3 months to 1 year and 0.82 mmHg (95% CI 0.58-1.06) for 1-5 years. Most of the associations between weight gain and blood pressure were mediated through weight at the age of 6.5 years. Findings for girls and diastolic blood pressure were similar.

CONCLUSIONS

Children who gained weight faster than their peers, particularly at later ages, had higher blood pressure at the age of 6.5 years, with no association between birthweight and blood pressure.

Origins of disparities in cardiovascular disease: birth weight, body mass index, and young adult systolic blood pressure in the national longitudinal study of adolescent health

PURPOSE

We evaluated the contributions of birth weight and current body mass index (BMI) to racial/ethnic disparities in systolic blood pressure (SBP) in the United States.

METHODS

Participants were 10,046 young adults (ages 24-32) in the National Longitudinal Study of Adolescent Health. SBP, BMI, and other contemporaneous factors were assessed at Wave IV (2007-2008); birth weight and other early life factors were reported at Wave I (1994-1995). Data were analyzed using sex- and race-stratified multivariable regression models.

RESULTS

Racial/ethnic disparities in SBP were limited to black and white females. The black-white female disparity in SBP was 3.36 mmHg and was partially explained by current BMI, but not birth weight. Associations between birth weight and SBP were limited to males, in whom we found a decrease of 1.05 mmHg in SBP per 1-kg increase in birth weight (95% confidence interval, -1.90, -0.20). This inverse relationship strengthened after adjusting for BMI and other factors, and was strongest among black and white males. A significant association between BMI and SBP was found in all racial/ethnic and sex subgroups.

CONCLUSIONS

In this U.S. national cohort, birth weight is negatively associated with SBP among black and white young adult males.

Ecological analysis of the relationship between infant mortality and cardiovascular disease mortality at ages 45-69 in the Brazilian 1935 birth cohort

BACKGROUND

International ecological studies have shown a positive association between infant mortality as a proxy for low birth weight and cardiovascular disease mortality in adult life.

METHODS

Mortality rates due to Cardiovascular Diseases (CVDMR) standardised by age in adults between 45 and 69 years of age and by place of birth (pob) and residence (res) were related to Infant Mortality Rates (IMR) in the Brazilian 1935 birth cohort.

RESULTS

Two relationship patterns were noted between IMR and CVDMR: for the Southeast, South and Centre-West group of regions (r(pob)=0.46; r(res)=0.29) and for the North and Northeast group of regions (r(pob)=0.21; r(res)=0.33). For the latter pattern, two states were identified (Rio Grande do Norte and Paraíba) as atypical areas, whose exclusion strengthened the association (r(pob)=0.73; r(res)=0.91).

CONCLUSIONS

The direction of the associations changed after the analysis by group of Brazilian regions (indirect control of socio-economic levels, coverage and quality of the information). There is a positive, although weak association between IMR and CVDMR. Attempts to control or minimise the interference of migratory movements, cohort effects and socio-economic levels represented methodological progress in ecological analyses of foetal programming in Brazil.

Evaluating the indirect effect of infant weight velocity on insulin resistance in young adulthood: a birth cohort study from the Philippines

The authors assessed the relation between infant weight velocity and adult insulin resistance, specifically evaluating whether adult size and body fat distribution mediated the association. Data were from the Cebu Longitudinal Health and Nutrition Survey (Cebu, the Philippines), in which a birth cohort was followed to age 22 years (n=1,409; 1983-2005). Insulin resistance was measured using homeostasis model assessment of insulin resistance (HOMA-IR). Weight velocity (g/month) from 0 to 4 months and from 0 to 24 months was assessed. The authors examined direct and total associations between early growth and adult HOMA-IR in linear regression models and used a nonparametric bootstrapping procedure to test indirect effects through adult body mass index (BMI; weight (kg)/height (m)(2)) and waist circumference. Infant weight velocity was positively associated with adult BMI and waist circumference, which positively predicted HOMA-IR. There were no total or direct effects of immediate postnatal weight velocity (0-4 months) on adult HOMA-IR, although indirect effects through BMI and waist circumference were significant. Weight velocity from 0 to 24 months positively predicted HOMA-IR among males only, while indirect effects were significant in both sexes. In a relatively lean sample of young adults from a population with rising rates of diabetes and cardiovascular disease, the authors found evidence for small indirect effects of infant weight velocity on adult insulin resistance mediated through adult BMI and waist circumference.

Maternal smoking during pregnancy, fetal arterial resistance adaptations and cardiovascular function in childhood

OBJECTIVE

To unravel the mechanisms underlying the previously demonstrated associations between low birthweight and cardiovascular disease in adulthood, we examined whether maternal smoking during pregnancy leads to fetal arterial resistance adaptations, and subsequently to fetal growth retardation and changes in postnatal blood pressure and cardiac development.

DESIGN

Prospective cohort study from early fetal life onwards.

SETTING

Academic hospital.

POPULATION

Analyses were based on 1120 children aged 2 years.

METHODS

Maternal smoking during pregnancy [non-smoking, first trimester smoking, continued smoking (< 5 and ≥ 5 cigarettes/day)] was assessed by questionnaire.

MAIN OUTCOME MEASURES

Third trimester placental and fetal arterial resistance indices and fetal growth were assessed by ultrasound and Doppler measurements. Postnatal blood pressure and cardiac structures (aortic root diameter, left atrial diameter, left ventricular mass) were measured at 2 years of age.

RESULTS

First trimester smoking was not associated with third trimester placental and fetal blood flow adaptations. Continued smoking of ≥ 5 cigarettes/day was associated with an increased resistance in uterine, umbilical and middle cerebral arteries, and with a decreased flow and diameter of the ascending aorta. Among mothers who continued to smoke, the third trimester estimated fetal weights and birthweights were most affected in children with the highest umbilical artery resistance. Fetal arterial resistance indices were also associated with aortic root diameter and left atrial diameter.

CONCLUSIONS

Fetal arterial resistance adaptations may be involved in the pathways leading from maternal smoking during pregnancy to low birthweight and cardiovascular developmental changes in childhood in the offspring.

Infant mortality, season of birth and the health of older Puerto Rican adults

The increasing prevalence of heart disease and diabetes among aging populations in low and middle income countries leads to questions regarding the degree to which endogenous early life exposures (exposures in utero) are important determinants of these health conditions. We devised a test using infant mortality (IMR) to verify if season of birth is a good indicator of early life (in utero) conditions that precipitate adult onset of disease. We linked annual IMR at the municipality (municipio) level from the late 1920s to early 1940s with individual birth year and place using a representative sample of older Puerto Rican adults (n = 1447) from the Puerto Rican Elderly: Health Conditions (PREHCO) study. We estimated the effects of season of birth on adult heart disease and diabetes for all respondents and then for respondents according to whether they were born when IMR was lower or higher, controlling for age, gender, obesity, respondent's educational level, adult behavior (smoking and exercise) and other early life exposures (childhood health, knee height and childhood socioeconomic status (SES)). The pattern of effects suggests that season of birth reflects endogenous causes: (1) odds of heart disease and diabetes were strong and significant for those born during the lean season in years when IMR was lower; (2) effects remained consistent even after controlling for other childhood conditions and adult behavior; but (3) no seasonality effects on adult health for adults born when IMR was higher. We conclude that in this population of older Puerto Rican adults there is continued support that the timing of adverse endogenous (in utero) conditions such as poor nutrition and infectious diseases is associated with adult heart disease and diabetes. It will be important to test the validity of these findings in other similar populations in the developing world.

Amplification of the association between birthweight and blood pressure with age: the Bogalusa Heart Study

OBJECTIVES

Although low birthweight is associated with elevated blood pressure (BP) levels, whether the strength of this relationship is amplified with age is still debated. This study tested the hypothesis that the magnitude of the birthweight-BP association increases with age from childhood to adulthood.

METHODS

The study cohort included 6251 individuals (64.5% whites and 35.6% blacks, 50.0% males) enrolled in the Bogalusa Heart Study. Individuals were examined 1-15 times for BP from childhood to adulthood, with 24 363 observations. Information on birthweight and gestational age was obtained from Louisiana State birth certificates.

RESULTS

After adjusting for race, sex, age and gestational age, low birthweight (kg) was associated with higher SBP levels (mmHg) in adolescence (aged 12-17 years, regression coefficient β = -0.80, P = 0.004) and adulthood (aged 18-50 years, β = -1.34, P = 0.010). Adjustment for current BMI yielded considerably stronger association. Importantly, the magnitude of the birthweight-SBP relationship, measured as standardized β(unit = SD), was significantly amplified with increasing age, regardless of adjustment for current BMI and race. Further, the strengthened association (the increase in standardized β ranging 0.02-0.12) by adjustment for current BMI was closely related to the BMI-SBP and birthweight-BMI correlations, especially noted in childhood.

CONCLUSION

These findings on the potentiating effect of increasing age on the birthweight-BP relationship suggest that the fetal programming and the increasing cumulative burden with age of unhealthy lifestyle behaviors affect the development of adult hypertension in a synergistic manner.

The long-term effects of prematurity and intrauterine growth restriction on cardiovascular, renal, and metabolic function

Objective. To determine relative influences of intrauterine growth restriction (IUGR) and preterm birth on risks of cardiovascular, renal, or metabolic dysfunction in adolescent children. Study Design. Retrospective cohort study. 71 periadolescent children were classified into four groups: premature small for gestational age (SGA), premature appropriate for gestational age (AGA), term SGA, and term AGA. Outcome Measures. Systolic blood pressure (SBP), augmentation index (Al), glomerular filtration rate (GFR) following protein load; plasma glucose and serum insulin levels. Results. SGA had higher SBP (average 4.6 mmHg) and lower GFR following protein load (average 28.5 mL/min/1.73 m²) than AGA. There was no effect of prematurity on SBP (P = .4) or GFR (P = .9). Both prematurity and SGA were associated with higher AI (average 9.7%) and higher serum insulin levels 2 hr after glucose load (average 15.5 mIU/L) than all other groups. Conclusion. IUGR is a more significant risk factor than preterm birth for later systolic hypertension and renal dysfunction. Among children born preterm, those who are also SGA are at increased risk of arterial stiffness and metabolic dysfunction.

Effects of current size, postnatal growth, and birth size on blood pressure in early childhood

OBJECTIVE

In a prospective study, we investigated the impact of early growth on blood pressure at 3 years of age.

METHODS

We measured systolic blood pressure (SBP) and diastolic blood pressure (DBP) for 590 children 3 years of age and related measurements to current size and size at birth, 6 months, 1 year, and 2 years of age.

RESULTS

SBP was related positively to weight at 3 and 2 years and, after adjustment for current size, negatively to weight at birth and 6 months but not at 1 or 2 years. No effect was observed for DBP. A family history of hypertension was associated with higher maternal blood pressure, greater weight, and gestational hypertension (P = .05). Mothers with a history of gestational hypertension had higher SBP and DBP values (P < .001). In multivariate linear regression analyses, SBP was influenced positively by weight at 3 years and family history of hypertension and negatively by weight at 6 months. None of the factors was associated with DBP.

CONCLUSIONS

For 3-year-old children, current weight was a determinant of SBP and postnatal growth to 6 months of age was more predictive than birth weight. A family history of hypertension is important in determining maternal blood pressure. These observations suggest a window in which postnatal growth might be modified.

Adiposity, insulin resistance and cardiovascular risk factors in 9-10-year-old Indian children: relationships with birth size and postnatal growth

Lower birthweight, and rapid childhood weight gain predict elevated cardiovascular risk factors in children. We examined associations between serial, detailed, anthropometric measurements from birth to 9.5 years of age and cardiovascular risk markers in Indian children. Children (n = 663) born at the Holdsworth Memorial Hospital, Mysore, India were measured at birth and 6-12 monthly thereafter. At 9.5 years, 539 (255 boys) underwent a 2-h oral glucose tolerance test, and blood pressure (BP) and fasting lipid concentrations were measured. Insulin resistance was calculated using the HOMA equation. These outcomes were examined in relation to birth measurements and changes in measurements (growth) during infancy (0-2 years), 2-5 years and 5-9.5 years using conditional s.d. scores. Larger current weight, height and skinfold thickness were associated with higher risk markers at 9.5 years (P < 0.05). Lower weight, smaller length and mid-arm circumference at birth were associated with higher fasting glucose concentrations at 9.5 years (P ⩽ 0.01). After adjusting for current weight/height, there were inverse associations between birthweight and/or length and insulin concentrations, HOMA, systolic and diastolic BP and plasma triglycerides (P < 0.05). Increases in conditional weight and height between 0-2, 2-5 and 5-9.5 years were associated with higher insulin concentrations, HOMA and systolic BP. In conclusion, in 9-10-year-old Indian children, as in other studies, cardiovascular risk factors were highest in children who were light or short at birth but heavy or tall at 9 years. Greater infant and childhood weight and height gain were associated with higher risk markers.

Maternal undernutrition and the offspring kidney: from fetal to adult life

Maternal dietary protein restriction during pregnancy is associated with low fetal birth weight and leads to renal morphological and physiological changes. Different mechanisms can contribute to this phenotype: exposure to fetal glucocorticoid, alterations in the components of the renin-angiotensin system, apoptosis, and DNA methylation. A low-protein diet during gestation decreases the activity of placental 11ß-hydroxysteroid dehydrogenase, exposing the fetus to glucocorticoids and resetting the hypothalamic-pituitary-adrenal axis in the offspring. The abnormal function/expression of type 1 (AT1(R)) or type 2 (AT2(R)) AngII receptors during any period of life may be the consequence or cause of renal adaptation. AT1(R) is up-regulated, compared with control, on the first day after birth of offspring born to low-protein diet mothers, but this protein appears to be down-regulated by 12 days of age and thereafter. In these offspring, AT2(R) expression differs from control at 1 day of age, but is also down-regulated thereafter, with low nephron numbers at all ages: from the fetal period, at the end of nephron formation, and during adulthood. However, during adulthood, the glomerular filtration rate is not altered, due to glomerulus and podocyte hypertrophy. Kidney tubule transporters are regulated by physiological mechanisms; Na(+)/K(+)-ATPase is inhibited by AngII and, in this model, the down-regulated AngII receptors fail to inhibit Na(+)/K(+)-ATPase, leading to increased Na(+) reabsorption, contributing to the hypertensive status. We also considered the modulation of pro-apoptotic and anti-apoptotic factors during nephrogenesis, since organogenesis depends upon a tight balance between proliferation, differentiation and cell death.

Hypertension, diabetes and overweight: looming legacies of the Biafran famine

BACKGROUND

Sub-Saharan Africa is facing rapidly increasing prevalences of cardiovascular disease, obesity, diabetes and hypertension. Previous and ongoing undernutrition among pregnant women may contribute to this development as suggested by epidemiological studies from high income countries linking undernutrition in fetal life with increased burden of non-communicable diseases in later life. We undertook to study the risks for hypertension, glucose intolerance and overweight forty years after fetal exposure to famine afflicted Biafra during the Nigerian civil war (1967-1970).

METHODS AND FINDINGS

Cohort study performed in June 27-July 31, 2009 in Enugu, Nigeria. Adults (n = 1,339) born before (1965-67), during (1968-January 1970), or after (1971-73) the years of famine were included. Blood pressure (BP), random plasma glucose (p-glucose) and anthropometrics, as well as prevalence of hypertension (BP>140/90 mmHg), impaired glucose tolerance (IGT; p-glucose 7.8-11.0 mmol/l), diabetes (DM; p-glucose ≥11.1 mmol/l), or overweight (BMI>25 kg/m(2)) were compared between the three groups. Fetal-infant exposure to famine was associated with elevated systolic (+7 mmHg; p<0.001) and diastolic (+5 mmHg; p<0.001) BP, increased p-glucose (+0.3 mmol/L; p<0.05) and waist circumference (+3 cm, p<0.001), increased risk of systolic hypertension (adjusted OR 2.87; 95% CI 1.90-4.34), IGT (OR 1.65; 95% CI 1.02-2.69) and overweight (OR 1.41; 95% CI 1.03-1.93) as compared to people born after the famine. Limitations of this study include the lack of birth weight data and the inability to separate effects of fetal and infant famine.

CONCLUSIONS

Fetal and infant undernutrition is associated with significantly increased risk of hypertension and impaired glucose tolerance in 40-year-old Nigerians. Prevention of undernutrition during pregnancy and in infancy should therefore be given high priority in health, education, and economic agendas.

Association of maternally inherited GNAS alleles with African-American male birth weight

OBJECTIVE

Human birth weight variation has a significant genetic component and important clinical consequences. We performed a survey of single nucleotide polymorphisms (SNPs) in 14 candidate genes to identify associations with birth weight variation.

METHODS

SNP variation was surveyed in 221 healthy African-American mother-newborn pairs. Genes were selected based on previous association with obesity-related traits, significant differences in circulating protein levels in low birth weight pregnancies or association with newborn size in model organisms or growth disorders in humans. Association was tested via multiple linear regression with adjustment for significant covariables.

RESULTS

Under a dominant model SNP rs7754561 of ENPPI was significantly associated with birth weight. Among imprinted loci, maternal genotypes for SNP rs6026576 of GNAS were significantly associated with birth weight (additive and dominant models). This association was restricted to male offspring. Analyses that distinguished between alleles of paternal and maternal origin demonstrated that only maternally-transmitted alleles were associated with birth weight and that this association was restricted to male newborns.

CONCLUSION

The effect of only maternally-transmitted alleles of GNAS may be a consequence of the complex splicing and imprinting pattern of the GNAS gene, although the reason this effect is observed only among male newborns is unclear.

Low birth weight is associated with components of the metabolic syndrome

The purpose of the study was to investigate the association between birth weight and number of metabolic syndrome (MetS) components in an urban Chinese cohort. Individuals (N = 2019) who were born between 1921 and 1954 at the Peking Union Medical College Hospital and who had detailed obstetric records volunteered to take part and were examined by medical personnel in a clinical setting between May 2003 and April 2005. Data of birth outcome and results on clinic examination in adulthood were analyzed using analysis of variance and multivariate ordinal regression to estimate the association between birth weight and MetS. Metabolic syndrome was defined as per the National Cholesterol Education Program Adult Treatment Panel III. The prevalence of MetS was 26.74%, whereas 55.43% of the subjects had at least 2 components of MetS. Subjects who presented with all 5 components of MetS exhibited a significantly lower birth weight and higher age, body mass index, and waist circumference at follow-up. Multivariate ordinal regression analysis revealed that, as compared with those with birth weights of 3000 to 3500 g, subjects who had birth weights of less than 2500 g were 66% more likely to develop a greater number of MetS components in adulthood (95% confidence interval, 1.18-2.34; P = .004), whereas those with birth weights between 2500 and 3000 g were 33% more likely to develop a greater number of MetS components as adults (95% confidence interval, 1.09-1.63; P = .005). The present study demonstrated the relationship between low birth weight and increased presentation of MetS components in Chinese adults.

Fetal and life course origins of serum lipids in mid-adulthood: results from a prospective cohort study

Background

During the past two decades, the hypothesis of fetal origins of adult disease has received considerable attention. However, critique has also been raised regarding the failure to take the explanatory role of accumulation of other exposures into consideration, despite the wealth of evidence that social circumstances during the life course impact on health in adulthood. The aim of the present prospective cohort study was to examine the contributions of birth weight and life course exposures (cumulative socioeconomic disadvantage and adversity) to dyslipidemia and serum lipids in mid-adulthood.

Methods

A cohort (effective n = 824, 77%) was prospectively examined with respect to self-reported socioeconomic status as well as stressors (e.g., financial strain, low decision latitude, separation, death or illness of a close one, unemployment) at the ages of 16, 21, 30 and 43 years; summarized in cumulative socioeconomic disadvantage and cumulative adversity. Information on birth weight was collected from birth records. Participants were assessed for serum lipids (total cholesterol, low- and high-density lipoprotein cholesterol and triglycerides), apolipoproteins (A1 and B) and height and weight (for the calculation of body mass index, BMI) at age 43. Current health behavior (alcohol consumption, smoking and snuff use) was reported at age 43.

Results

Cumulative life course exposures were related to several outcomes; mainly explained by cumulative socioeconomic disadvantage in the total sample (independently of current health behaviors but attenuated by current BMI) and also by cumulative adversity in women (partly explained by current health behavior but not by BMI). Birth weight was related only to triglycerides in women, independently of life course exposures, health behaviors and BMI. No significant association of either exposure was observed in men.

Conclusions

Social circumstances during the life course seem to be of greater importance than birth weight for dyslipidemia and serum lipid levels in adulthood.

Multinutrient fortification of human breast milk for preterm infants following hospital discharge

BACKGROUND

Preterm infants are usually growth restricted at hospital discharge. Feeding preterm infants after hospital discharge with multinutrient fortified breast milk rather than unfortified breast milk may facilitate more rapid catch-up growth and improve neurodevelopmental outcomes.

OBJECTIVES

To determine the effect of feeding with multinutrient fortified human breast milk versus unfortified breast milk on growth and development in preterm or low birth weight infants following hospital discharge.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2010), MEDLINE (1966 to April 2010), EMBASE (1980 to April 2010), CINAHL (1982 to April 2010), conference proceedings, and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared feeding preterm infants following hospital discharge with multinutrient fortified breast milk compared with unfortified human breast milk.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Neonatal Review Group were used, with separate evaluation of trial quality and data extraction by two review authors.

MAIN RESULTS

One small trial (N = 39) was identified. Multinutrient fortification of breast milk for 12 weeks after hospital discharge resulted in higher rates of growth during infancy. At 12 months corrected age, weight (mean difference 1187g, 95% confidence interval (CI) 259, 2115 g), length (3.8 cm, 95%CI 1.2, 6.4 cm) and head circumference (1.0 cm, 95%CI 0.1, 1.9 cm) were statistically significantly greater in the intervention group. No evidence of an effect on neurodevelopmental assessments at 18 months corrected age was found.

AUTHORS' CONCLUSIONS

The limited available data suggest that feeding preterm infants following hospital discharge with multinutrient fortified breast milk compared with unfortified breast milk increases growth rates during infancy. The importance of these effects on long-term growth and development is unclear and deserves further assessment in randomised controlled trials. Since fortifying breast milk for infants fed directly from the breast is logistically difficult and has the potential to interfere with breast feeding, it is important to determine if mothers would support further trials of this intervention.

Fetal origins of renal disparities

Epidemiologic studies of populations continue to emerge showing that early-life factors influence the risk of developing several chronic diseases of adulthood. Susceptibility to environmental factors is particularly problematic during renal development, which is not complete until 36 weeks of gestation. Environmental deprivation may lead to adaptations including early growth restriction, whereas late insults may alter the kidney during the final stages of development. Because disparities among those who are more likely to have low birth weight mirrors the disparities observed among those more likely to develop kidney-related disorders, fetal origins have been presumed to explain some of the observed disparities. Although current empiric evidence supports a link between fetal programming and childhood/adult kidney disease, affected pathways may vary by race.

Estimated birth weight and adult cardiovascular risk factors in a developing southern Chinese population: a cross sectional study

Background

Birth weight is negatively associated with cardiovascular diseases and diabetes, but the associations are less well-established in developing populations where birth weight is often unavailable. We studied the association of birth weight and cardiovascular risk, using birth rank as an instrumental variable, in Southern China.

Methods

We used published data on birth weight by birth rank from an appropriate population and baseline data from the Guangzhou Biobank Cohort Study phases 2 & 3 (2005-8) to examine the adjusted associations, using instrumental variable analysis, of birth weight with clinically measured cardiovascular risk factors and the metabolic syndrome in older (≥ 50 years) men (n = 5,051) and women (n = 13,907).

Results

Estimated birth weight was associated with lower blood pressure (systolic -0.25 mm Hg 95% confidence interval (CI), -0.53 to 0.03 and diastolic -0.33 mm Hg 95% CI -0.48 to -0.18 per standard deviation higher birth weight), but had little association with glucose, lipids, waist-hip ratio, body mass index or the metabolic syndrome, adjusted for age, sex, early environment and number of offspring.

Conclusion

Birth weight may impact blood pressure; however associations of birth weight with other cardiovascular risk factors may not be related to foetal exposures, but speculatively could be an historical co-incidence, with corresponding implications for prevention.