Maternal smoking during pregnancy in relation to child overweight: follow-up to age 8 years

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.

Maternal and Early Childhood Risk Factors for Overweight and Obesity among Low-Income Predominantly Black Children at Age Five Years: A Prospective Cohort Study

Objective. To identify maternal and early childhood risk factors for obesity and overweight among children at age 5 in the state of Alabama. Methods. We recruited 740 mothers during early pregnancy from University of Alabama Prenatal Clinics in a prospective cohort study and followed them throughout pregnancy. We followed their children from birth until 5 years of age. The main outcome measure was obesity (BMI for age and sex ≥ 95th percentile) at 5 years of age. We used poisson regression with robust variance estimation to compute risk ratio (RR). Results. At the 5th year of followup, 71 (9.6%) of the children were obese and 85 (11.5%) were overweight (BMI ≥ 85th-<95th percentile). In multivariable analysis, maternal prepregnancy overweight (RR: 2.30, 95% CI: 1.29-4.11) and obesity (RR: 2.53, 95% CI: 1.49-4.31), and child's birth weight >85th percentile (RR: 2.04, 95% CI: 1.13-3.68) were associated with childhood obesity. Maternal prepregnancy BMI, birth weight, and maternal smoking were associated with the child being overweight 1-12 cigarettes/day versus 0 cigarettes/day (RR: 1.40, 95% CI: 1.02-1.91). Conclusion. Children of overweight and obese mothers, and children with higher birth weight, are more likely to be obese and overweight at age 5. Maternal smoking 1-12 cigarettes per day is associated with the child being overweight.

Maternal smoking during pregnancy predicts adult offspring cardiovascular risk factors - evidence from a community-based large birth cohort study

Background

Maternal smoking during pregnancy is associated with offspring obesity. However, little is known about whether maternal smoking in pregnancy predicts other offspring cardiovascular risk factors including waist circumference (WC), waist-hip-ratio (WHR), pulse rate (PR), systolic (SBP), and diastolic blood pressure (DBP).

Methods

We studied a sub-sample of 2038 (50% males) young adults who were born in Brisbane, Australia to investigate the prospective association of maternal smoking during pregnancy with young adult cardiovascular risk factors. We compared offspring mean BMI, WC, WHR, SBP, DBP and PR and the risk of being overweight and obese at 21 years by three mutually exclusive categories of maternal smoking status defined as never smoked, smoked before and/or after pregnancy but not in pregnancy or smoked during pregnancy and other times.

Results

Offspring of mothers who smoked during pregnancy had greater mean BMI, WC, WHR and PR and they were at greater risk of being obese at 21 years compared to offspring of those mothers who never smoked. The mean of these risk factors among those adult offspring whose mothers stopped smoking during pregnancy, but who then smoked at other times in the child's life, were similar to those mothers who never smoked. These results were independent of a range of potential confounding factors.

Conclusion

The findings of this study suggest a prospective association of maternal smoking during pregnancy and offspring obesity as well as PR in adulthood, and reinforce the need to persuade pregnant women not to smoke.

Role of environmental chemicals in diabetes and obesity: a National Toxicology Program workshop review

BACKGROUND

There has been increasing interest in the concept that exposures to environmental chemicals may be contributing factors to the epidemics of diabetes and obesity. On 11-13 January 2011, the National Institute of Environmental Health Sciences (NIEHS) Division of the National Toxicology Program (NTP) organized a workshop to evaluate the current state of the science on these topics of increasing public health concern.

OBJECTIVE

The main objective of the workshop was to develop recommendations for a research agenda after completing a critical analysis of the literature for humans and experimental animals exposed to certain environmental chemicals. The environmental exposures considered at the workshop were arsenic, persistent organic pollutants, maternal smoking/nicotine, organotins, phthalates, bisphenol A, and pesticides. High-throughput screening data from Toxicology in the 21st Century (Tox21) were also considered as a way to evaluate potential cellular pathways and generate -hypotheses for testing which and how certain chemicals might perturb biological processes related to diabetes and obesity.

CONCLUSIONS

Overall, the review of the existing literature identified linkages between several of the environmental exposures and type 2 diabetes. There was also support for the "developmental obesogen" hypothesis, which suggests that chemical exposures may increase the risk of obesity by altering the differentiation of adipocytes or the development of neural circuits that regulate feeding behavior. The effects may be most apparent when the developmental exposure is combined with consumption of a high-calorie, high-carbohydrate, or high-fat diet later in life. Research on environmental chemical exposures and type 1 diabetes was very limited. This lack of research was considered a critical data gap. In this workshop review, we outline the major themes that emerged from the workshop and discuss activities that NIEHS/NTP is undertaking to address research recommendations. This review also serves as an introduction to an upcoming series of articles that review the literature regarding specific exposures and outcomes in more detail.

Maternal smoking during pregnancy and childhood obesity: results from the CESAR Study

Childhood obesity is a worldwide public health concern. Recent studies from high income countries have demonstrated associations between maternal smoking during pregnancy and children's excess body weight. We examine associations between maternal smoking during pregnancy and children's overweight or obesity, in six countries in the less affluent Central/Eastern European region. Questionnaire data were analysed, for 8,926 singleton children aged 9-12 years. Country-specific odds ratios for effects of maternal smoking during pregnancy on being overweight, and on obesity, were estimated using logistic regression. Heterogeneity between country-specific results, and mean effects (allowing for heterogeneity) were estimated. Positive associations between maternal smoking and overweight were seen in all countries but Romania. While not individually statistically significant, the mean odds ratio was 1.26 (95% CI 1.03-1.55), with no evidence of between-country heterogeneity. Obese children were few (2.7%), and associations between obesity and maternal smoking during pregnancy were more heterogeneous, with odds ratios ranging from 0.71 (0.32-1.57) in Poland to 5.49 (2.11-14.30) in Slovakia. Between-country heterogeneity was strongly related to average persons-per-room, a possible socioeconomic indicator, with stronger associations where households were less crowded. Estimates of dose-response relationships tended to be small and non-significant, even when pooled. Our results provide evidence of a link between maternal smoking in pregnancy and childhood overweight. Associations with obesity, though strong in some countries, were less consistent. Maternal smoking may confer an addition to a child's potential for obesity, which is more likely to be realised in affluent conditions.

Tobacco smoke exposure before, during, and after pregnancy and risk of overweight at age 6

Maternal smoking during pregnancy has been associated with overweight and obesity in childhood and is strongly correlated with children's tobacco smoke exposure before and after pregnancy. We investigated the independent association of tobacco smoke exposure at various pre- and postnatal periods and overweight at age 6. A total of 1,954 children attending the 2001-2002 school entrance health examination in the city of Aachen, Germany, were included into this study. Height and weight were measured, BMI was calculated. Tobacco smoke exposure at various periods, other lifestyle and sociodemographic factors were ascertained by questionnaire. Multiple logistic regression models were used to assess the association between tobacco smoke exposure and overweight. Prevalence of overweight was 8.9%. Significant positive associations were found with maternal smoking before and during pregnancy and during the first and sixth year of life. When all smoking periods were included into one logistic model simultaneously, secondhand smoke exposure after birth remained positively associated with overweight at age 6 at either one of the two time periods (first year only: odds ratio (OR) (95% confidence interval (CI)): 2.94 (1.30-6.67), sixth year only: 2.57 (1.64-4.04), respectively) or at both (4.43 (2.24-8.76)). Exposure to tobacco smoke during the first years of life appears to be a key risk factor for development of childhood overweight.

Obesity in rural youth: looking beyond nutrition and physical activity

Contributors to excessive obesity in rural youth include well-documented nutrition and physical activity behaviors. However, emerging research suggests that preventing excessive weight gain and smoking during pregnancy, teen pregnancy, and child abuse also could reduce obesity in this vulnerable population. These traditional and emerging, nontraditional factors need to be addressed within the confines of current challenges faced by rural communities. An enhanced ecological model provides a framework for combining traditional and nontraditional factors into a more comprehensive approach that addresses the complexity of the issues contributing to youth obesity.

Sparse Variational Analysis of Linear Mixed Models for Large Data Sets

It is increasingly common to be faced with longitudinal or multi-level data sets that have large numbers of predictors and/or a large sample size. Current methods of fitting and inference for mixed effects models tend to perform poorly in such settings. When there are many variables, it is appealing to allow uncertainty in subset selection and to obtain a sparse characterization of the data. Bayesian methods are available to address these goals using Markov chain Monte Carlo (MCMC), but MCMC is very computationally expensive and can be infeasible in large p and/or large n problems. As a fast approximate Bayes solution, we recommend a novel approximation to the posterior relying on variational methods. Variational methods are used to approximate the posterior of the parameters in a decomposition of the variance components, with priors chosen to obtain a sparse solution that allows selection of random effects. The method is evaluated through a simulation study, and applied to an epidemiological application.

Parental smoking during pregnancy, early growth, and risk of obesity in preschool children: the Generation R Study

BACKGROUND

Maternal smoking during pregnancy seems to be associated with obesity in offspring. Not much is known about the specific critical exposure periods or underlying mechanisms for this association.

OBJECTIVE

We assessed the associations of active maternal and paternal smoking during pregnancy with early growth characteristics and risks of overweight and obesity in preschool children.

DESIGN

This study was a population-based, prospective cohort study from early fetal life until the age of 4 y in 5342 mothers and fathers and their children. Growth characteristics [head circumference, length, weight, and body mass index (BMI; in kg/m(2))] and overweight and obesity were repeatedly measured at the ages of 1, 2, 3, and 4 y.

RESULTS

In comparison with children from nonsmoking mothers, children from mothers who continued smoking during pregnancy had persistently smaller head circumferences and heights until the age of 4 y, whereas their weights were lower only until the age of 3 mo. This smaller length and normal to higher weight led to an increased BMI [SD score difference: 0.11; 95% CI: 0.02, 0.20; P < 0.05)] and an increased risk of obesity (odds ratio: 1.61; 95% CI: 1.03, 2.53; P < 0.05) at the age of 4 y. In nonsmoking mothers, paternal smoking was not associated with postnatal growth characteristics or risk of obesity in offspring. Maternal smoking during pregnancy was associated with a higher BMI at the age of 4 y in children with a normal birth weight and in those who were small for gestational age at birth.

CONCLUSION

Our findings suggest that direct intrauterine exposure to smoke until late pregnancy leads to different height and weight growth adaptations and increased risks of overweight and obesity in preschool children.

Parental smoking during pregnancy and offspring bone mass at age 10 years: findings from a prospective birth cohort

We investigated an intrauterine influence of maternal smoking during pregnancy on childhood bone mass. Daughters, but not sons, of mothers who smoked had higher bone mass at age 10years. This appears to be due to familial factors related to parental smoking influencing increased offspring adiposity rather than a direct intrauterine effect.

INTRODUCTION

Neonatal studies have demonstrated an adverse relationship between maternal smoking in pregnancy and foetal bone mineral accrual. We aimed to investigate an intrauterine influence of maternal smoking during pregnancy on offspring bone mass at mean age 9.9 years.

METHODS

We compared associations of maternal and paternal smoking in pregnancy with offspring total body less head (TBLH) and spine bone mineral content (BMC), bone area (BA), bone mineral density (BMD) and area-adjusted BMC (ABMC) in 7,121 children in the Avon Longitudinal Study of Parents and Children.

RESULTS

Maternal smoking in any trimester was associated with increased TBLH BMC, BA and BMD in girls (mean difference [95% CI] (sex-specific SD scores), 0.13 [0.05-0.22], 0.13 [0.04-0.21], 0.13 [0.04-0.22], respectively) but not boys (0.01 [-0.07-0.09], 0.00 [-0.08-0.08], 0.04 [-0.05-0.12]), and also with spine BMC, BA and BMD in girls (0.13 [0.03-0.23], 0.12 [0.03-0.22], 0.10 [0.00-0.21]) but not boys (0.03 [-0.06-0.12], 0.00 [-0.09-0.09], 0.05 [-0.04-0.14]), but not with ABMC. Paternal smoking associations were similar, with no statistical evidence for a difference between maternal and paternal effects. Maternal associations increased on adjustment for offspring birth weight and gestational age, but attenuated to the null after adjustment for current height and weight.

CONCLUSIONS

We found little evidence that maternal smoking was related to bone mass in boys. In girls, maternal smoking associations were similar to those of paternal smoking, suggesting that these were attributable to shared familial characteristics, not intrauterine mechanisms.

Reproducibility of reported in utero exposure to tobacco smoke

PURPOSE

In studies of the fetal origins of disease and life course epidemiology, measures of fetal exposure may be based on information reported by the adults who were exposed in utero. In particular, the full spectrum of consequences of in utero exposure to maternal tobacco smoking is now an area of active investigation, and the ability to report such exposure reproducibly is of interest. We evaluated the reproducibility of in utero exposure to tobacco smoke, reported by the adult daughter during consecutive pregnancies.

METHODS

This study was based on 11,257 women who enrolled for more than one pregnancy in the Norwegian Mother and Child Cohort Study (MoBa). Participants completed a questionnaire around 17 weeks of gestation, which asked about their in utero exposure to tobacco smoke. Kappa statistics were calculated. Determinants of agreement were evaluated using logistic regression.

RESULTS

Weighted Kappa for in utero exposure for the first and second reports was 0.80. Determinants of agreement were higher education (better) and longer time between reports (worse).

CONCLUSIONS

Information on in utero exposure to maternal tobacco smoking provided by adult women was highly reproducible in this population.

Is low birth weight in the causal pathway of the association between maternal smoking in pregnancy and higher BMI in the offspring?

A number of cross-sectional and prospective studies suggested a priming effect of maternal smoking in pregnancy on offspring's obesity. It has been hypothesized that this association might be explained by low birth weight and subsequent catch-up growth in the causal pathway. We therefore examined the role of birth weight in children exposed versus not exposed to cigarette smoking in utero on later body mass index (BMI). Using data of 12,383 children and adolescents (3-17 years of age) recorded in a German population-based survey (KiGGS), we assessed mean body mass index standard deviation scores (BMI-SDS) in different birth weight SDS categories, stratified for children with smoking and non-smoking mothers. We calculated spline regression models with BMI-SDS as outcome variable, cubic splines of birth weight SDS, and potential confounding factors. Children whose mothers had been smoking during pregnancy had lower birth weight SDS and higher BMI-SDS at interview compared to children of non-smoking mothers. However, we observed a linear association between birth weight SDS and BMI-SDS in crude analyses for both groups. Similarly, almost linear effects were observed in adjusted spline regression analyses, except for children with very low birth weight. The respective 95% confidence bands did not preclude a linear effect for the whole birth weight SDS distribution. Our findings suggest that low birth weight is unlikely to be the main cause for the association between intrauterine nicotine exposure and higher BMI in later life. Alternative mechanisms, such as alterations in the noradrenergic system or increased food efficiency, have to be considered.

Gestational glucose tolerance and cord blood leptin levels predict slower weight gain in early infancy

OBJECTIVE

To determine the extent to which known prenatal and perinatal predictors of childhood obesity also predict weight gain in early infancy.

STUDY DESIGN

We studied 690 infants participating in the prospective cohort Project Viva. We measured length and weight at birth and at 6 months. Using multivariable linear regression, we examined relationships of selected maternal and infant factors with change in weight-for-length z-score (WFL-z) from 0 to 6 months.

RESULTS

Mean (standard deviation) change in WFL-z from 0 to 6 months was 0.23 (1.11), which translates to 4500 grams gained from birth to 6 months of life in an infant with average birth weight and length. After adjustment for confounding variables and birth weight-for-gestational age z-score (-0.28 [95% confidence interval, -0.37, -0.19] per unit), cord blood leptin (-0.40 [95%confidence interval, -0.61, -0.19] per 10 ng/mL), and gestational diabetes -0.50 [95%confidence interval, -0.88, -0.11] versus normal glucose tolerance)were each associated with slower gain in WFL-z from 0 to 6 months.

CONCLUSIONS

Higher neonatal leptin and gestational diabetes predicted slower weight gain in the first 6 months of life. The hormonal milieu of the intrauterine environment may determine growth patterns in early infancy and thus later obesity.

Potential latent effects of prenatal cocaine exposure on growth and the risk of cardiovascular and metabolic disease in childhood

The literature strongly suggests that prenatal exposure to certain medications and substances does not cause major malformations in early childhood. However, these exposures may have far-reaching latent health effects, such as restricted growth, hypertension, and cardiovascular events in adulthood. We reviewed the literature to identify the effects of prenatal cocaine exposure on growth and the risk of cardiovascular and metabolic disease in late adolescence and early adulthood by examining studies that were published in peer-reviewed English-language journals from 1990 through 2009 and indexed in MEDLINE. We found that animal and clinical studies of the influence of prenatal cocaine exposure on child and adolescent growth and the subsequent development of myocardial and cardiometabolic disease risk factors are few and inconclusive. Studies support the hypothesis that vascular and hemodynamic functions are partially programmed in early life and thus substantially influence vascular aging and arterial stiffening in later life. Sub-optimal fetal nutrition and growth may increase blood pressure and the development of cardiovascular and metabolic disease in late life. How prenatal cocaine and other drug exposure effects this relationship is currently unknown. Despite high rates of cocaine and other drug use during pregnancy (up to 18% in some studies), little is known about the health effects of prenatal cocaine exposure in adolescence and early adulthood. The few studies of early growth deficits persisting into adolescence are inconclusive. The literature provides little information on how exposed children grow into adulthood and about their subsequent risk of cardiometabolic and vascular disease.

Persistent Organochlorine Exposure and Pregnancy Loss: A Prospective Cohort Study

Polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) are suspected reproductive toxicants. We assessed serum concentration of 76 PCB congeners, DDE, and risk of human chorionic gonadotropin confirmed pregnancy loss among 79 women followed for up to 12 menstrual cycles or until pregnancy. 55 women had live births, 14 experienced pregnancy losses, and 10 did not achieve pregnancy. PCBs and DDE were quantified using gas chromatography with electron capture. PCBs were grouped a priori by biologic activity. Cox proportional hazard regression adjusting for age (categorized 24 - 29, 30 - 34) and average standardized alcohol and cigarette intake (continuous) was used to estimate hazard ratios (HR) of pregnancy loss. Estrogenic PCBs (HR = 1.66, 95% CI: 0.68, 4.02), anti-estrogenic PCBs (HR = 0.10, 95% CI: <0.01, 67.07) and DDE (HR = 1.43, 95% CI: 0.45, 4.52) were not statistically significantly associated with pregnancy loss. Our results provide some signal that estrogenic and antiestrogenic PCBs may be differentially associated with pregnancy loss. Further research is needed to elucidate these associations.

Childhood obesity and parental smoking as risk factors for childhood ADHD in Liverpool children

ADHD prevalence has risen in parallel with rising prevalence of pregnancy smoking and childhood obesity. The objective was to determine the epidemiological association of pregnancy smoking and childhood obesity with ADHD. A cross-sectional community study was conducted in 2006 using a parental questionnaire. A total of 1,074 schoolchildren aged 5-11 years were enrolled from 15 primary schools in a lower socio-economic area of Merseyside. ADHD was defined by the question "does your child have Attention Deficit Hyperactivity Disorder, (ADHD), which has been diagnosed by a doctor?" The prevalence estimates for childhood obesity, maternal smoking during pregnancy and childhood ADHD were 14.9% (116/777), 28.0% (269/955), and 3.4% (32/945), respectively. ADHD prevalence increased fivefold in children with obesity (RR, 4.80, 95% CI 2.2-10.4, P < 0.001) and more than twofold in children of mothers who smoked during pregnancy (RR, 2.44, 95% CI 1.2-4.9, P = 0.02). Regression analysis adjusting for obesity, overweight, maternal smoking during pregnancy, heavy maternal smoking, household member smoking during pregnancy, doctor-diagnosed asthma, preterm birth, and low birthweight showed significant independent associations of ADHD prevalence with obesity (AOR, 4.66, 95% CI 1.57-13.89, P = 0.006) and pregnancy smoking (AOR, 3.19, 95% CI 1.08-9.49, P = 0.04). There was a positive dose-response association of ADHD with the number of maternal cigarettes smoked during pregnancy. Measures to reduce both smoking among pregnant women and childhood obesity might reduce prevalence of childhood ADHD.

Dose response association of pregnancy cigarette smoke exposure, childhood stature, overweight and obesity

BACKGROUND

The combined dose response effects of pregnancy cigarette smoke exposure on childhood overweight, obesity and short stature have not been reported.

METHOD

A community based cross-sectional survey of 3038 children aged 5-11 years from 15 primary schools in Merseyside, UK. Self-completed parental questionnaires were used for family characteristics, socio-economic status and parental smoking practices. Children were measured for height and weight and z-scores calculated for parental smoking categories.

RESULTS

Of 689 (34.0%) mothers who smoked during pregnancy 50.5% smoked ten or more cigarettes daily (heavy smokers). Children of maternal non-smokers had prevalence estimates for overweight, obesity and short stature of 25, 9.6 and 3.2%, respectively. Prevalence estimates were higher in children of mothers who were heavy smokers during pregnancy, 31.5% (P = 0.001), 15.6% (P < 0.001) and 5.5% (P = 0.001), respectively. Mean height for age z-scores was lower among heavy maternal (P < 0.001) and paternal smokers (P < 0.01) compared to non-smokers. Childhood overweight, obesity or short stature were all associated with heavy maternal smoking during pregnancy (all P < 0.001). Mean body mass index (BMI) z-scores were higher in boys of mothers who smoked (P = 0.043). The adjusted odds ratio for short stature in children of heavy maternal smokers was 2.76 (95% CI 1.21-6.33) and 4.28 (1.37-13.37) if both parents were heavy smokers. The adjusted OR for obesity in children of maternal smokers was 1.61(1.19-2.18). The population attributable risk for short stature was 8.8% (1.1-22.7) for heavy maternal smokers.

CONCLUSION

A dose-response association was observed between pregnancy smoking exposure, short stature and obesity.

Prenatal environmental tobacco smoke exposure and early childhood body mass index

Maternal smoking during pregnancy is associated with increased risk of childhood overweight body mass index (BMI). Less is known about the association between prenatal secondhand tobacco smoke (SHS) exposure and childhood BMI. We followed 292 mother-child dyads from early pregnancy to 3 years of age. Prenatal tobacco smoke exposure during pregnancy was quantified using self-report and serum cotinine biomarkers. We used linear mixed models to estimate the association between tobacco smoke exposure and BMI at birth, 4 weeks, and 1, 2 and 3 years. During pregnancy, 15% of women reported SHS exposure and 12% reported active smoking, but 51% of women had cotinine levels consistent with SHS exposure and 10% had cotinine concentrations indicative of active smoking. After adjustment for confounders, children born to active smokers (self-report or serum cotinine) had higher BMI at 2 and 3 years of age, compared with unexposed children. Children born to women with prenatal serum cotinine concentrations indicative of SHS exposure had higher BMI at 2 (mean difference [MD] 0.3 [95% confidence interval -0.1, 0.7]) and 3 (MD 0.4 [0, 0.8]) years compared with unexposed children. Using self-reported prenatal exposure resulted in non-differential exposure misclassification of SHS exposures that attenuated the association between SHS exposure and BMI compared with serum cotinine concentrations. These findings suggest active and secondhand prenatal tobacco smoke exposure may be related to an important public health problem in childhood and later life. In addition, accurate quantification of prenatal secondhand tobacco smoke exposures is essential to obtaining valid estimates.

Does early-life exposure to organophosphate insecticides lead to prediabetes and obesity?

Human exposures to organophosphate insecticides are ubiquitous. Although regarded as neurotoxicants, increasing evidence points toward lasting metabolic disruption from early-life organophosphate exposures. We gave neonatal rats chlorpyrifos, diazinon or parathion in doses devoid of any acute signs of toxicity, straddling the threshold for barely-detectable cholinesterase inhibition. Organophosphate exposure during a critical developmental window altered the trajectory of hepatic adenylyl cyclase/cyclic AMP signaling, culminating in hyperresponsiveness to gluconeogenic stimuli. Consequently, the animals developed metabolic dysfunction resembling prediabetes. When the organophosphate-exposed animals consumed a high fat diet in adulthood, metabolic defects were exacerbated and animals gained excess weight compared to unexposed rats on the same diet. At the same time, the high fat diet ameliorated many of the central synaptic defects caused by organophosphate exposure, pointing to nonpharmacologic therapeutic interventions to offset neurodevelopmental abnormalities, as well as toward fostering dietary choices favoring high fat intake. These studies show how common insecticides may contribute to the increased worldwide incidence of obesity and diabetes.

Risk profiles for overweight/obesity among preschoolers

BACKGROUND

The epidemic of overweight/obesity among U.S. children has led to an alarming increase in health-related consequences, including early-onset diabetes and cardiovascular disease. Recent research has identified the independent contribution of several maternal and child factors to the development of childhood overweight/obesity. Few studies, however, have examined risk profiles of childhood obesity.

AIM

This study used classification and regression tree (CART) analysis to examine the combined effect of maternal and child factors in generating risk profiles for overweight/obesity among preschoolers.

STUDY DESIGN

Data from the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B) study were used. The sample was comprised of preschool children. CART and logistic regression models were built and compared.

RESULTS

Children who were overweight/obese at two years of age had an increased risk of being overweight/obese at four years of age. Children born to overweight/obese mothers were more likely to be overweight/obese by age four, even if their BMI at two years of age was normal. Children with high birth weight (> or = 4000 g.) were also more likely to be overweight/obese at age four years if they were born to mothers with a normal pregravid BMI, but were of a lower socioeconomic status. Among preschoolers whose mothers were black or white and who had a high pregravid BMI, breastfeeding duration and parity played an important role in determining their risk of being overweight/obese.

CONCLUSIONS

Classification tree analysis confirms and extends current knowledge of preschool overweight/obesity by providing preliminary risk profiles that are structured within the context of prenatal and postnatal maternal and child characteristics.

Prenatal exposure to the major DDT metabolite 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and growth in boys from Mexico

Recent data suggest that prenatal exposure to p,p'-DDE may reduce height and increase body mass index (BMI) in childhood, thus potentially raising the risk of adult health problems. The association between prenatal DDE exposure and growth was evaluated in 788 boys from Chiapas, an area of Mexico where DDT was recently used. The median DDE levels in maternal serum at birth (2002-2003) were 2.7 microg/g lipid. 2633 measurements of height (cm) and weight (kg) were obtained in 2004-2005. The median age of the children during follow-up was 18 months (quartiles 14 and 22 months). Height and body mass index (kg/m(2)) were age-standardized and expressed as standard deviation scores (SDS). Multivariate random-effect models for longitudinal data were fitted and predicted height and BMI SDS were estimated from the adjusted models. Overall, associations between prenatal DDE level and height or BMI SDS at any given age were not observed. For example, the predicted values showed that children with the highest exposure (DDE: >9.00 microg/g) compared to those least exposed (DDE: <3.01 microg/g) grew similarly and they had a BMI SDS similar to the referent group. The results do not support the prior findings of an association of DDE exposure with childhood height or BMI.

Paternal smoking and childhood overweight: evidence from the Hong Kong "Children of 1997"

OBJECTIVE

This study examined, in a non-Western sociohistorical context, whether prenatal or postnatal secondhand smoke (SHS) exposure for children of nonsmoking mothers was associated with higher childhood BMI, and it clarified whether the observed associations were biologically mediated or socioeconomically confounded.

METHODS

A total of 6710 and 6519 children of nonsmoking mothers (N = 7924) with BMI data at approximately 7 and approximately 11 years, respectively, from a population-representative (N = 8327), Hong Kong Chinese birth cohort ("Children of 1997"), born in April or May 1997, were included in the analysis.

RESULTS

Compared with no SHS exposure, daily paternal smoking increased mean BMI z scores, but not height, at 7 years (difference: 0.10 [95% confidence interval: 0.02-0.19]) and at 11 years (difference: 0.16 [95% confidence interval: 0.07-0.26]), with adjustment for gender, birth order, socioeconomic position, mother's place of birth, breastfeeding, serious morbidity, and pubertal status.

CONCLUSIONS

Our findings, although preliminary, suggest that the association of paternal smoking with child overweight might be biologically mediated. Given the known harms of smoking, reducing SHS exposure from conception as a precautionary action for childhood overweight might be warranted.

Mother's age at menarche and offspring size

Objective

An individual’s growth trajectory is, at least in part, inherited. Mother’s early age at menarche has been associated with taller offspring height and greater body mass index (BMI) at age 9 years, suggesting that mother’s age at menarche may be an intergenerational marker of growth. We examined the association between mother’s age at menarche and childhood size at birth, and at the ages 1, 3, 4, 7, and 8 years in the Collaborative Perinatal Project (CPP).

Subjects

We examined 128,636 measurements from 31,474 Black and White children. We transformed the original measurements into z-scores. Child size was examined in mixed models, adjusted for center, child sex, race, socioeconomic index, child’s exact age at measurement (in months), mother's age at recruitment and, depending on which measure was the outcome in the specific model, mother's height, pre-pregnancy weight, or BMI.

Results

Compared with children whose mother had menarche at age 15 or later, children whose mothers had age at menarche before age 12 were taller from age 1 and had higher BMI at ages 7 and 8 (0.17 and 0.19 z, respecively).

Conclusions

Mother’s age at menarche is a modest predictor of their children’s growth trajectory. The mechanism is likely to be heritable, although other explanations are possible.

Maternal smoking during pregnancy and offspring obesity: meta-analysis

BACKGROUND

Recent reports have suggested that maternal smoking may increase the risk of development of obesity in the unborn child in later life, but relatively few cohort studies have been done on the relationship between maternal smoking during pregnancy and future development of metabolic syndrome.

METHODS

A systematic review and meta-analysis of observational studies reporting effect estimates and 95% confidence intervals (95%CI) was conducted on the association between maternal smoking during pregnancy and obesity of future offspring.

RESULTS

Seventeen papers were identified from 444 English-language papers (key word search: maternal smoking and obesity) in PubMed. All papers showed a positive association between maternal smoking during pregnancy and childhood obesity. The meta-analysis, using the DerSimonian-Laird method, found the association to be statistically significant. In association with maternal smoking during pregnancy and body mass index with more than 95%CI in the offspring aged 3-33 years, the pooled odds ratio calculated from 16 of these 17 studies was 1.64 (95%CI: 1.42-1.90). After adjustment for publication bias, the pooled adjusted odds ratio was 1.52 (95%CI: 1.36-1.70). In addition, confounders of maternal obesity, low social status, low birthweight and not being breast-fed seemed to be risk factors for offspring obesity.

CONCLUSION

Maternal smoking during pregnancy may cause future obesity and metabolic syndrome.

Breast-feeding and overweight in Singapore school children

BACKGROUND

Studies from developed Western countries have shown inconsistent associations between breast-feeding and overweight/obesity in children and adolescents. Few data are available from Asian populations. The purpose of the present study was therefore to evaluate the association between breast-feeding and overweight/obesity in a study of 10-12-year-old children in Singapore.

METHODS

A total of 797 school children (49% girls, 76% Chinese) who participated in the Singapore Cohort Study of the Risk Factors for Myopia (SCORM) were examined. Overweight/obesity (n = 179) was defined as age-sex-specific body mass index (BMI) cut-offs corresponding to BMI of 25 kg/m(2) for overweight and 30 kg/m(2) for obesity at age 18 based on the International Obesity Task Force (IOTF) reference.

RESULTS

The prevalence of overweight/obesity was 22.5%. Overall, breast-feeding was not found to be associated with overweight/obesity. After adjusting for potential confounders, the multivariable odds ratio (95% confidence interval) of overweight/obesity was 1.14 (0.80-1.63) for ever breast-fed compared with never breast-fed, 1.00 (0.57-1.72) for breast-fed for >3 months compared to < or =3 months and 0.79 (0.47-1.34) for exclusive/mostly breast-fed compared to partly breast-fed.

CONCLUSIONS

No significant associations were detected among breast-feeding, its type, and duration with overweight/obesity in this Asian cohort of 10-12-year-old children.

Maternal obesity is necessary for programming effect of high-fat diet on offspring

We tested the hypothesis that maternal consumption of dietary fat, independent from obesity, increases serum leptin in neonatal pups and predisposes them to adult obesity. Female rats either were fed a high-fat (HF) diet or a low-fat (LF) diet or were fed the HF diet but pair fed (PF) to the caloric intake of the LF group for 4 wk before breeding and throughout gestation and lactation. Dams consuming the HF diet had increased adiposity and were hyperphagic. At weaning, pups born to obese dams had significantly higher body fat and serum leptin levels and reduced insulin tolerance compared with offspring of LF-fed dams. Pups were weaned onto a chow diet until 8 wk of age, when they were then fed either HF or LF diet. At 18 wk of age, offspring from obese HF dams weighed more than offspring from nonobese LF or PF dams, and offspring eating HF diet weighed significantly more than those eating LF diet. Consequently, HF-fed offspring of obese HF dams weighed the most and LF-fed offspring from obese HF dams were similar in weight to HF-fed offspring from nonobese LF dams. These data suggest that maternal obesity exerts an independent effect on offspring body weight that is of similar magnitude as the effect of the offspring's adult diet. Furthermore, there was no difference in body weight between the nonobese LF and PF offspring on either diet. Together, these data suggest that maternal adiposity, and not dietary fat per se, induces hyperleptinemia and insulin resistance in offspring, as well as an increased body weight that persists into adulthood.

Maternal smoking cessation in early pregnancy and offspring weight status at four years of age. A prospective birth cohort study

BACKGROUND

Maternal smoking during pregnancy is associated with fetal growth restriction, but also with increased risk for overweight in childhood. If the mother stops smoking in early pregnancy fetal growth is not restricted, but whether the risk for later overweight persists is unclear.

AIM

To study if four year old children of mothers who stopped smoking in early pregnancy have higher mean body mass index (BMI) and/or increased odds of being overweight compared with children of non-smokers.

STUDY DESIGN

Prospective population based study on Norwegian mothers and children.

SUBJECTS

Among 711 children available for analysis, 540 were children of never smoking mothers, 114 of mothers who stopped smoking in early pregnancy, and 57 of mothers who continued to smoke throughout pregnancy.

OUTCOME MEASURES

BMI and overweight defined by international criteria at age four.

RESULTS

Compared with children of never smoking mothers, children of smoking mothers had higher mean BMI (mean difference: 0.47; 95% CI: 0.10, 0.84 kg/m(2)), whereas mean BMI was not higher among children of mothers who stopped smoking (mean difference: 0.02; 95% CI: -0.24, 0.28 kg/m(2). Similarly, children of smoking mothers had increased odds for overweight (adjusted OR: 2.83; 95% CI: 1.13, 7.10), whereas children of mothers who stopped smoking did not have increased odds (adjusted OR: 1.29; 95% CI: 0.62, 2.68) compared with children of never smoking mothers.

CONCLUSIONS

In this study, the association between smoking exposure and childhood overweight did not persist in children of mothers who stopped smoking early in pregnancy.

Dose-response associations between maternal smoking during pregnancy and subsequent childhood obesity: effect modification by maternal race/ethnicity in a low-income US cohort

Studies suggest that children exposed to cigarette smoke in utero are at risk of becoming obese. Few researchers have evaluated the dose-response association between maternal smoking during pregnancy and childhood obesity or whether this association varies by maternal race/ethnicity. The authors obtained retrospective cohort data by linking records from the Pregnancy Nutrition Surveillance System and the Pediatric Nutrition Surveillance System on 155,411 low-income children born during 1995-2001 in 9 US states and 2 tribal nations. The authors examined maternal smoking status, duration of smoking, quantity of smoking, and both duration and quantity combined. Childhood obesity was based on a body mass index greater than or equal to the 95th percentile for sex and age, assessed at age 2-4 years. Maternal race/ethnicity modified the association between smoking during pregnancy and childhood obesity. Among non-Hispanic White mothers, both duration and quantity of smoking were positively associated with childhood obesity in a dose-response manner. Among non-Hispanic Black mothers, only heavy smoking was positively associated with childhood obesity. Among Hispanics, American Indians/Alaska Natives, and Asians/Pacific Islanders, smoking was not associated with childhood obesity. The inconsistent association between smoking during pregnancy and childhood obesity across race/ethnicity categories merits further investigation into potential explanations for this variation, which may include confounding, reporting bias, or unexplored biologic mechanisms.

Exposure of neonatal rats to parathion elicits sex-selective reprogramming of metabolism and alters the response to a high-fat diet in adulthood

BACKGROUND

Developmental exposures to organophosphate pesticides are virtually ubiquitous. These agents are neurotoxicants, but recent evidence also points to lasting effects on metabolism.

OBJECTIVES

We administered parathion to neonatal rats. In adulthood, we assessed the impact on weight gain, food consumption, and glucose and lipid homeostasis, as well as the interaction with the effects of a high-fat diet.

METHODS

Neonatal rats were given parathion on postnatal days 1-4 using doses (0.1 or 0.2 mg/kg/day) that straddle the threshold for barely detectable cholinesterase inhibition and the first signs of systemic toxicity. In adulthood, animals were either maintained on standard lab chow or switched to a high-fat diet for 7 weeks.

RESULTS

In male rats on a normal diet, the low-dose parathion exposure caused increased weight gain but also evoked signs of a prediabetic state, with elevated fasting serum glucose and impaired fat metabolism. The higher dose of parathion reversed the weight gain and caused further metabolic defects. Females showed greater sensitivity to metabolic disruption, with weight loss at either parathion dose, and greater imbalances in glucose and lipid metabolism. At 0.1 mg/kg/day parathion, females showed enhanced weight gain on the high-fat diet; This effect was reversed in the 0.2-mg/kg/day parathion group, and was accompanied by even greater deficits in glucose and fat metabolism.

CONCLUSIONS

Neonatal low-dose parathion exposure disrupts glucose and fat homeostasis in a persistent and sex-selective manner. Early-life toxicant exposure to organophosphates or other environmental chemicals may play a role in the increased incidence of obesity and diabetes.

Maternal smoking, demographic and lifestyle factors in relation to daughter's age at menarche

A previous study suggested a younger age at menarche (AAM) among daughters of heavy prenatal smokers, especially among non-Whites. The present study was designed to evaluate that association in another population and to examine other factors that may be related to AAM. We analysed data from the Collaborative Perinatal Project, a nationwide longitudinal study of pregnant women and their children conducted in 1959-66. At three sites, with a predominance of Black participants (80%), AAM was ascertained in the offspring when they were young adults. We included data on 1556 daughters who had a mean AAM of 12.7 years (standard deviation 1.8). Amount smoked by the mothers was obtained from a baseline interview and subsequent prenatal visits. Regression models were run including maternal smoking and other covariates, for only the prenatal period, as well as in models with some childhood characteristics. In the prenatal factor model, younger mean AAM in daughters was found with maternal characteristics of earlier AAM, being married, and of lower parity. Examining childhood variables, earlier AAM was found among girls with few or no siblings or with higher socio-economic status. Unlike our previous findings, mean AAM was later in daughters of heavy smokers (20+ cigarettes/day), with a delay of 0.31 years [95% confidence interval (CI) 0.008, 0.61], or about 3.7 months in the prenatal model, and 0.34 years [95% CI -0.02, 0.66] in the model with childhood variables included. The pattern was consistent by race. A number of prenatal and childhood factors related to AAM were identified that should be considered when examining exogenous exposures in relation to pubertal onset.

Maternal smoking during pregnancy and children's cognitive and physical development: a causal risk factor?

There remains considerable debate regarding the effects of maternal smoking during pregnancy on children's growth and development. Evidence that exposure to maternal smoking during pregnancy is associated with numerous adverse outcomes is contradicted by research suggesting that these associations are spurious. The authors investigated the relation between maternal smoking during pregnancy and 14 developmental outcomes of children from birth through age 7 years, using data from the Collaborative Perinatal Project (1959-1974; n = 52,919). In addition to adjusting for potential confounders measured contemporaneously with maternal smoking, the authors fitted conditional fixed-effects models among siblings that controlled for unmeasured confounders. Results from the conditional analyses indicated a birth weight difference of -85.63 g associated with smoking of >or=20 cigarettes daily during pregnancy (95% confidence interval: -131.91, -39.34) and 2.73 times' higher odds of being overweight at age 7 years (95% confidence interval: 1.30, 5.71). However, the associations between maternal smoking and 12 other outcomes studied (including Apgar score, intelligence, academic achievement, conduct problems, and asthma) were entirely eliminated after adjustment for measured and unmeasured confounders. The authors conclude that the hypothesized effects of maternal smoking during pregnancy on these outcomes either are not present or are not distinguishable from a broader range of familial factors associated with maternal smoking.

The effect of birthweight upon insulin resistance and associated cardiovascular risk factors in adolescence is not explained by fetal growth velocity in the third trimester as measured by repeated ultrasound fetometry

AIMS/HYPOTHESIS

Smallness for gestational age (SGA) is associated with increased risk of developing components of the metabolic syndrome. Although SGA can imply intrauterine growth restriction (IUGR), more information is required to link specific fetal growth patterns to adult outcomes.

METHODS

We examined the impact of fetal growth velocity during the third trimester (FGV) vs birthweight for gestational age on early markers of the metabolic syndrome in 123 healthy men and women (mean age 17.5 years) born at term. FGV was determined by ultrasound measurements.

RESULTS

After correction for confounders including current BMI, SGA was significantly associated with raised basal plasma insulin (+19% above appropriate for gestational age), homeostasis model assessment of insulin resistance (+21%), cholesterol:HDL-cholesterol ratio (+13%) and systolic BP (+4.8%) (all p < 0.05). Furthermore SGA was associated with increased fat mass (+9.6%) and trunk-fat per cent (+6.8%) and with reduced lean body mass as determined by dual-energy X-ray absorptiometry scans (-4.1% below appropriate for gestational age) (all p < 0.05). In contrast, IUGR in the third trimester was associated only with an elevated cholesterol:HDL-cholesterol ratio (+11% above not-IUGR).

CONCLUSIONS/INTERPRETATION

In the present study, FGV did not explain the impact of birthweight upon the metabolic phenotype in adolescence. This suggests that fetal growth prior to the third trimester or postnatal catch-up growth plays a more important role.

Developmental origins of childhood overweight: potential public health impact

Several modifiable pre- and postnatal determinants of childhood overweight are known, but no one has examined how they influence risk of overweight in combination. We estimated the risk of overweight at age 3 years according to levels of maternal smoking during pregnancy, gestational weight gain, breastfeeding duration, and infant sleep duration. We studied 1,110 mother-child pairs in Project Viva, a prospective prebirth cohort study. The main outcome measure was child overweight (BMI for age and sex >or=95th percentile) at age 3. We ran logistic regression models with all four modifiable risk factors as well as the covariates maternal BMI and education, child race/ethnicity, and household income. From the model, we obtained the estimated probability of overweight for each of the 16 combinations of the four risk factors. During pregnancy, 9.8% of mothers smoked and 50% gained excessive weight. In infancy, 73% mother-child pairs breastfed for <12 m, and 31% of infants slept <12 h/day. Among the 3-year-old children in the cohort, 9.5% were overweight. In the prediction model, the estimated probability of overweight ranged from 0.06 among children exposed to favorable levels of all four risk factors, to 0.29 with adverse levels of all four. Healthful levels of four behaviors during early development predicted much lower probability of overweight at age 3 than adverse levels. Interventions to modify several factors during pregnancy and infancy could have substantial impact on prevention of childhood overweight.

Maternal smoking very early in pregnancy is related to child overweight at age 5-7 y

BACKGROUND

Despite being associated with lower birth weight, maternal smoking in the last 2 trimesters of pregnancy has been associated with increased risk of offspring overweight in several studies. To date, only one study has examined whether smoking in the first trimester only, which is not associated with birth weight, is also associated with childhood overweight.

OBJECTIVE

This study uses prospective data to examine associations between maternal smoking in the first compared with later trimesters of pregnancy and child overweight at age 5-7 y.

DESIGN

Data from a prospective cohort of 369 Spanish children born in 1997-1998 were used. Logistic regression was used to estimate associations between maternal smoking during different time periods and odds of child overweight later in life.

RESULTS

Maternal smoking during the first trimester was more strongly associated with overweight (adjusted odds ratio: 2.65; 95% CI: 1.26, 5.54) than smoking later in pregnancy (1.88, 0.85, 4.15). Smoking limited to the first month of pregnancy was also associated with child overweight. Neither paternal smoking nor maternal smoking before or after pregnancy was associated with child overweight. Significant interactions with breastfeeding duration indicated that first-trimester smoking was associated with overweight only among children breastfed for <6 mo, suggesting prolonged breastfeeding may help to counter adverse effects of smoking in early pregnancy.

CONCLUSIONS

These data suggest maternal smoking very early in pregnancy may increase risk of later overweight in children and provide further support for promoting smoking cessation before rather than during early pregnancy. Further studies are needed to confirm these results.

Maternal smoking during pregnancy and child overweight: systematic review and meta-analysis

OBJECTIVE

Perform a systematic review of studies reporting on the association between maternal prenatal cigarette smoking and child overweight.

DESIGN

Meta-analysis of observational studies.

DATA SOURCES

Medline search and review of reference lists among studies published through June 2006.

REVIEW METHODS

Included studies reported an association between maternal smoking during pregnancy and risk of overweight among children at least 2 years of age. We did not include in the meta-analysis studies that provided only a continuous measure of adiposity, although those studies are discussed separately.

RESULTS

Based on results of 84 563 children reported in 14 observational studies, children whose mothers smoked during pregnancy were at elevated risk for overweight (pooled adjusted odds ratio (OR) 1.50, 95% CI: 1.36, 1.65) at ages 3-33 years, compared with children whose mothers did not smoke during pregnancy. The pooled estimate from unadjusted odds ratios (OR 1.52, 95% CI: 1.36, 1.69) was similar to the adjusted estimate, suggesting that sociodemographic and behavioral differences between smokers and nonsmokers did not explain the observed association. Although we observed evidence for publication bias, simulating a symmetric set of studies yielded a similar estimate (OR 1.40, 95% CI: 1.26, 1.55).

CONCLUSIONS

Prenatal smoking exposure appears to increase rates of overweight in childhood. In parts of the world undergoing the epidemiologic transition, the continuing increase in smoking among young women could contribute to spiraling increases in rates of obesity-related health outcomes in the 21st century.

Parental smoking and childhood obesity--is maternal smoking in pregnancy the critical exposure?

BACKGROUND

The concept of priming of childhood obesity by prenatal exposure to maternal smoking is based on a number of consistent studies. A recent paper found similar associations between paternal smoking and childhood obesity, questioning the presumed causal effect attributed to the prenatal exposure. Is the relation to paternal smoking consistent? Does it explain the effect of maternal smoking before or in pregnancy?

METHODS

Data from a cross sectional study on 5899 children in the setting of the 2005 school entrance health examinations in Bavaria were analysed. Associations between paternal smoking or maternal smoking before or in pregnancy and childhood obesity were assessed with adjustment for potential confounders.

RESULTS

The children's mean age was 5.8 years. The unadjusted odds ratio for obesity and paternal smoking was 2.0 (95% CI: 1.5, 2.6) and similar to that for maternal smoking before or in pregnancy with 2.3 (95% CI: 1.8, 3.1). After adjustment for a number of potential confounders and paternal smoking at interview the odds ratio for maternal smoking before or in pregnancy and childhood obesity was 1.9 (95% CI: 1.3, 2.7). There was no evidence for interaction between paternal smoking and maternal smoking before or in pregnancy (P = 0.38).

CONCLUSIONS

Although of similar magnitude, the association of paternal smoking could only partially explain the effect of maternal smoking before or in pregnancy on childhood obesity. Whether this persistent association reflects residual confounding or causality is unclear.

Association of maternal lifestyles including smoking during pregnancy with childhood obesity

OBJECTIVE

To examine the extent to which maternal smoking during early pregnancy and other prepregnancy lifestyle habits are associated with obesity and overweight in 5-year-old Japanese children.

RESEARCH METHOD AND PROCEDURES

We studied 1417 mother-child pairs enrolled in Project Enzan--a prospective cohort study. The dependent variables, childhood overweight and obesity, were defined with an international cut-off value. Maternal smoking during early pregnancy and other prepregnancy lifestyle habits were used as independent variables.

RESULTS

Maternal smoking habits were associated with overweight in the 5-year-old children [adjusted odds ratio (OR): 2.15; 95% confidence interval (CI): 1.12 to 4.11]. Maternal sleep duration of >or=8 h/d negatively affected childhood overweight (adjusted OR: 0.71; 95% CI: 0.49 to 1.04). Children whose mothers skipped breakfast were likely to become overweight (adjusted OR: 1.78; 95% CI: 1.14 to 2.77). The results of childhood obesity analysis were similar to those of childhood overweight analysis.

DISCUSSION

The results of this study suggest that there are effects of smoking during early pregnancy and other maternal lifestyle habits on the onset of childhood obesity in Japan. Therefore, interventions in maternal lifestyle habits are required to prevent childhood obesity, and these interventions should be initiated before pregnancy.

Maternal weight gain during pregnancy and overweight in Portuguese children

OBJECTIVE

The objective of our study was to assess the association between maternal weight gain during pregnancy and childhood overweight.

DESIGN

This study was a cross-sectional analysis.

SETTING

The data were derived from a community-based survey of children from primary schools of Portugal.

SUBJECTS

The study was performed in a sample of 6-12-year-old Portuguese school children (2445 girls and 2400 boys; age was 8.5+/-0.91 years).

MEASUREMENTS

Height and weight were measured according to international standards, and body mass index (BMI) was calculated. The definition of overweight was based on average centiles according to the International Obesity Task Force cutoffs. Children's parents completed a self-administered questionnaire, which provided information on general family background characteristics, maternal weight gain during pregnancy and children's physical activity. The response rate was 70.6%. Children's dietary intake was measured using a 24-h dietary recall. Logistic regression models were fitted to estimate the magnitude of the association between maternal weight gain during pregnancy and overweight in their children, adjusting for confounders (gender, age, birthweight, order of birth, breastfeeding, smoking during pregnancy, physical activity, parental BMI, parental education, calcium to protein ratio and energy intake).

RESULTS

The prevalence of overweight (including obesity) was 29% in boys and 33% in girls. The odds favouring overweight (including obesity) increased significantly for those women who gained > or =16 kg during pregnancy, compared to those with <9 kg , even after adjustment for confounders (crude odds ratio (OR)=1.53, confidence interval (CI) 95% 1.27-1.84, P-trend <0.001; Adjusted OR=1.27, CI 95% 1.01-1.61, P-trend=0.038).

CONCLUSION

Large maternal weight gain during pregnancy (> or =16 kg) was significantly associated with higher risk of overweight in Portuguese children.

Are birth weight and maternal smoking during pregnancy associated with malnutrition and excess weight among school age children?

In the late 1980's child malnutrition was still prevalent in Brazil, and child obesity was beginning to rise in the richest regions of the country. To assess the extent of the nutritional transition during the period and the influence of birth weight and maternal smoking on the nutritional condition of schoolchildren, we estimated the prevalence of excess weight and malnutrition in a cohort of Brazilian schoolchildren from 1987 to 1989. We calculated the body mass index (BMI) of 8- to 10-year-old schoolchildren born in Ribeirão Preto in 1978/79. We considered children with a BMI <5th percentile (P5) to be malnourished, children with P5 > or = BMI<P85 to be thin and normal, and children with BMI > or = P85 to be overweight. We evaluated the association of these nutritional disorders with birth factors (infant weight, sex, preterm delivery, number of pregnancies, maternal smoking during pregnancy, marital status, and schooling) and type of school using nominal logistic regression. A total of 2797 schoolchildren were evaluated. There was a significant prevalence of malnutrition (9.5%) and excess weight already tended to increase (15.7%), while 6.4% of the children were obese. Excess weight was more prevalent among children attending private schools (odds ratio, OR = 2.27) and firstborn children (OR = 1.69). Maternal smoking during pregnancy protected against malnutrition (OR = 0.56), while children with lower birth weight were at higher risk for malnutrition (OR = 4.23). We conclude that a nutritional transition was under way while malnutrition was still present, but excess weight and related factors were already emerging.

Childhood Obesity: The Infancy Connection

The prevalence of overweight has risen to 19% in children aged 6 to 11 years and 17% in adolescents aged 12 to 19 years. This paper examines gestational and infancy factors that influence the risk of overweight in childhood. Important factors to eliminate the infancy connection to childhood obesity include the following: (a) maternal lifestyle patterns, (b) infant feeding transitions, and (c) environmental factors. Prevention efforts need to focus on practice, research, and public policy.

Tobacco smoke exposure of pregnant mothers and blood pressure in their newborns: results from the wheezing illnesses study Leidsche Rijn birth cohort

There is evidence to suggest that exposure of pregnant women to tobacco smoke is related to higher childhood blood pressure in their offspring. It is not well known whether this association is set in utero or by shared postnatal environments. The objective of this study was to assess the association between tobacco smoke exposure of pregnant mothers and blood pressure and heart rate of their newborns. In an unselected birth cohort, blood pressure and heart rate were measured in 456 infants at approximately 2 months of age. Smoking exposure of mothers in pregnancy was obtained by questionnaire. Of 456 mothers whose infants had blood pressure measured, 363 (79.6%) were not exposed to tobacco smoke in pregnancy, 63 (13.8%) did not smoke in pregnancy but were exposed by others, and 30 (6.6%) smoked. Infant offspring of mothers who had smoked during pregnancy had 5.4 mm Hg (95% CI: 1.2 to 9.7; P=0.01) higher systolic blood pressure levels than offspring of mothers who were not exposed to tobacco smoke in pregnancy, taking account of birth weight, infant age, gender, nutrition, and age of mother. No associations were found between maternal exposure to tobacco smoke in pregnancy and diastolic blood pressure. A positive association between maternal exposure to tobacco smoke and heart rate was largely explained by confounding. It can be concluded that maternal exposure to tobacco smoke in pregnancy has a substantial increasing effect on systolic blood pressure in early infancy.

Modeling low birth weights using threshold regression: results for U.S. birth data

Babies born live under 2,500 g or with a gestational age under 37 weeks are often inadequately developed and have elevated risks of infant mortality, congenital malformations, mental retardation, and other physical and neurological impairments. In this paper, we model birth weight as a first hitting time (FHT) of a birthing boundary in a Wiener process representing fetal development. We associate the parameters of the process and boundary with covariates describing maternal characteristics and the birthing environment using a relatively new regression methodology called threshold regression. Two FHT models for birth weight are developed. One is a mixture model and the other a competing risks model. These models are tested in a case demonstration using a 4%-systematic sample of the more than four million live births in the United States in 2002. An extensive data set for these births was provided by the National Center for Health Statistics. The focus of this paper is on the conceptual framework, models and methodology. A full empirical study is deferred to a later occasion.