Relationships between cigarette smoking during pregnancy, gestational age, maternal weight gain, and infant birthweight

Influence of Maternal Active and Secondhand Smoking during Pregnancy on Childhood Obesity at 3 Years of Age: A Nested Case-Control Study from the Japan Environment and Children's Study (JECS)

Maternal smoking during pregnancy is a risk factor for childhood obesity; however, the combined effect of secondhand smoking during pregnancy on children in the early years is unclear. We examined the effects of maternal active and secondhand smoking during pregnancy on childhood obesity in a large population-based cohort. A nested case–control study originating from the Japan Environment and Children’s Study was performed. The maternal smoking status was collected via self-administered questionnaires during mid/late pregnancy. Obesity in children was determined based on BMI measured at 3 years of age. In total, 4875 cases and 19,491 controls were included in the analyses. Conditional logistic regression models with a significance level of 5% (two-tailed test) were used to test the association. The proportion of mothers who continued smoking and who were exposed to secondhand smoking daily during pregnancy were 3.9% and 13.0% in cases and 2.9% and 10.8% in controls, respectively. Continuous maternal smoking was associated with increased odds of obesity compared to those who never smoked or quit smoking before the pregnancy (adjusted odds ratio, 1.39; 95% confidence interval, 1.01–1.92). The odds increased further when combined with secondhand smoking. The promotion of non-smoking among family members, in public and workplace could benefit pregnant women and offspring.

Spatial epidemiology of gestational age and birth weight in Switzerland: census-based linkage study

BACKGROUND

Gestational age and birth weight are strong predictors of infant morbidity and mortality. Understanding spatial variation can inform policies to reduce health inequalities. We examined small-area variation in gestational age and birth weight in Switzerland.

METHODS

All singleton live births recorded in the Swiss Live Birth Register 2011 to 2014 were eligible. We deterministically linked the Live Birth Register with census and survey data to create data sets including neonatal and pregnancy-related variables, parental characteristics and geographical variables. We produced maps of 705 areas and fitted linear mixed-effect models to assess to what extent spatial variation was explained by these variables.

RESULTS

We analysed all 315 177 eligible live births. Area-level averages of gestational age varied between 272 and 279 days, and between 3138 and 3467 g for birth weight. The fully adjusted models explained 31% and 87% of spatial variation of gestational age and birth weight, respectively. Language region accounted for most of the explained variation (23% in gestational age and 62% in birth weight), with shorter gestational age (-0.6 days and -0.9 days) and lower birth weight (-1.1% and -1.8%) in French-speaking and Italian-speaking areas, respectively, compared with German-speaking areas. Other variables explaining variation were, for gestational age, the level of urbanisation (10%) and parental nationality (3%). For birth weight, they were gestational age (27%), parental nationality (27%), civil status (10%) and altitude (10%). In a random sample of 81 968 live births with data on parental education, levels of education were only weakly associated with gestational age (-0.9 days for compulsory vs tertiary maternal education) or birth weight (-0.7% for compulsory vs tertiary maternal education).

CONCLUSIONS

In Switzerland, small area variation in birth weight is largely explained, and variation in gestational age partially explained, by geocultural, sociodemographic and pregnancy factors.

Biochemically confirmed smoking cessation and gestational weight gain

BACKGROUND

Prenatal smoking cessation has substantial health benefits for mothers and offspring, but concerns about weight gain may be a barrier to quitting. We quantified gestational weight gain associated with biochemically confirmed smoking cessation.

METHODS

Data originated from a randomized controlled cessation trial: Smoking Cessation in Pregnancy project (1987-1991). We calculated gestational weight gain using self-reported prepregnancy weight and measured weight at 30-34 weeks of gestation. We used linear regression to estimate adjusted mean differences in gain for quitters versus continuing smokers by the last trimester. The effects of quitting earlier (by 2nd trimester) versus later (by 3rd trimester) were calculated. We assessed the percentages who gained weight according to Institute of Medicine (IOM) recommendations within 2 weeks of a full-term delivery.

RESULTS

At 30-34 weeks, nulliparous and multiparous quitters gained an average of 3.0 pounds (95% CI 0.9-5.1 pounds) (1.4 kg [0.4-2.3 kg]) and 6.6 pounds (95% CI 4.3-8.9 pounds) (3.0 kg [1.9-4.0 kg]) more, respectively, than continuing smokers. Weight gain in early quitters did not differ significantly from that in late quitters. Quitters were more likely than continuing smokers to gain above current guidelines (60.3% vs 46.3%) and were less likely to gain below guidelines (11.5% vs 21.6%) (P = 0.002).

CONCLUSIONS

Although quitters had modest additional weight gain by 30-34 weeks compared to continuing smokers, a high proportion in both groups gained in excess of IOM recommendations. Both quitters and continuing smokers may need support to achieve optimal gestational weight gain.

Genetic variation affects congenital heart defect susceptibility in offspring exposed to maternal tobacco use

BACKGROUND

Congenital heart defects (CHDs) are among the most prevalent and serious birth defects, occurring in 8 to 10 of every 1000 live births in the United States. Epidemiologic studies have reported an association between CHDs and maternal smoking, but it remains unknown how genes impact the susceptibility of offspring to CHDs in the presence of maternal tobacco use.

METHODS

Using data from 403 case- and 219 control-parental triads enrolled in the National Birth Defects Prevention Study between 1998 and 2008, we investigated the association between CHDs and maternal and infant genetic variants involved in the tobacco metabolism and DNA repair pathways among mothers who smoked prenatally.

RESULTS

The maternal genotypes of single nucleotide polymorphisms in the excision repair cross-complementation group 1 (ERCC1), poly (ADP-ribose) polymerase 2 (PARP2), and ERCC5 genes were identified to be significantly associated with the occurrence of CHDs in the presence of maternal tobacco use. Our analysis also revealed a moderate association between the infant genotypes of polymorphisms in the O-sialoglycoprotein endopeptidase (OSGEP) gene and increased risk of CHDs among mothers who smoked.

CONCLUSION

Our study provides evidence that maternal and infant polymorphisms within the ERCC1, PARP2, ERCC5, and OSGEP genes are associated with CHD risk in the presence of maternal tobacco use. These results may provide insight into the susceptibility of having a pregnancy affected by CHDs among women who smoke.

An investigation into the influence of socioeconomic variables on gestational body mass index in pregnant women living in a peri-urban settlement, South Africa

Maternal and child mortality rates are still unacceptably high in South Africa. The health status of women in peri-urban areas has been influenced by political and socio-economic factors. Examining socio-economic variables (SEV) in a population aids in the explanation of the impact of social structures on an individual. Risk factors can then be established and pregnant women in these higher risk groups can be identified and given additional support during pregnancy. The aim of this study was to investigate the association between SEV and gestational Body Mass Index (GBMI) in a peri-urban settlement, South Africa. This was a sub-study of the Philani Mentor Mothers' Study (2009-2010). Maternal anthropometry and SEV were obtained from 1,145 participants. Multinomial regression was used to analyse the data. Household income was the only SEV that was significantly associated with GBMI. The odds of being underweight rather than normal weight during pregnancy increase by a factor of 2.145 (P < 0.05) for those who had a household income lower than R2000 per month. All other SEV were not significant. Logistic regression was therefore not carried out. Women who had a lower income were at risk of having a lower GBMI during pregnancy. This can lead to adverse birth outcomes such as premature birth, low birth weight, height and head circumference. Public health policy needs to be developed to include optimal nutrition health promotion strategies targeting women with a low income ante and post-natally. Once implemented, they need to be evaluated to assess the impact on maternal and child mortality.

Pregnancy, smoking and birth outcomes

This review summarizes the epidemiology and consequences of maternal smoking in pregnancy, with emphasis on the adverse effects on birth outcomes. In developed countries, approximately 15%, and in developing countries, approximately 8% of women smoke cigarettes, and adolescents and women from lower socioeconomic groups are more likely than other women to smoke while pregnant. Maternal smoking during pregnancy is the largest modifiable risk factor for intrauterine growth restriction. A meta-analysis of recent studies showed that the pooled estimate for reduction of mean birthweight was 174 g (95% confidence limits 132-220 g). Other studies confirm a weaker association between maternal smoking and preterm birth. The population attributable risk of low birthweight due to maternal smoking in the UK is estimated to be 29-39%. Tobacco smoke toxins damage the placenta and may lead to placental abruption, abortion or placenta praevia. Infants of mothers who smoke in pregnancy are at an increased risk of respiratory complications including asthma, obesity and, possibly, behavioral disorders. These effects may be dose-related, as there is good evidence that mean birthweight decrements are greater with increased numbers of cigarettes smoked during pregnancy. Cotinine is a useful indicator of tobacco smoke exposure in pregnant women and higher levels in body fluids have been related to lower birthweights. Maternal genetic polymorphisms of the cytochrome P (CYP)450 and glutathione-S-transferase (GST) subfamilies of metabolic genes influence the magnitude of the effect of nicotine exposure on birth outcomes through their influence on nicotine metabolism. Greatly increased risk of cigarette smoke-induced diseases, including low birthweight, has been found in individuals with susceptible genotypes. Interventions to control maternal smoking are also considered.

Factors that affect maternal insulin resistance and modify fetal growth and body composition

Fetal growth is multifactorial and can be altered by a variety of extrinsic and intrinsic factors. The maternal, placental, and fetal contribution to growth must all be considered. Of particular interest are maternal metabolic regulation and the availability of nutrients to the developing fetus. Weight gain, hyperlipidemia, and insulin resistance occur as a normal adaptation to pregnancy. Obesity and underlying insulin resistance among women of reproductive age are rapidly increasing, and the contribution of pregnancy on this abnormal metabolic background poses additional maternal and fetal challenges. Many components of the metabolic syndrome have been associated with changes in fetal growth, including obesity, dyslipidemia, hypertension, and insulin resistance or glucose intolerance. Additional factors affect fetal growth and include diet, exercise, and smoking. In this review, we briefly discuss the importance and descriptions of fetal growth, followed by a discussion of several of the extrinsic and intrinsic established factors affecting fetal growth. We highlight factors that may modify fetal growth and body composition directly or indirectly through alterations in maternal metabolism.

Valuing mother and child health: the intrauterine environment

The paper estimates the value a mother assigns to own health relative to child health. Estimation of relative health valuation requires the decomposition of a child health improvement into its direct effect on the child's health and its indirect effect, through improvements in maternal health. Failure to distinguish the impact of the direct and indirect effects can lead to biased estimates. We consider the intrauterine environment of a pregnant mother and her unborn child, where maternal health inputs are choice variables and her health affects child health. The empirical estimates suggest that mothers value child health up to six times higher than own health, and that the relative value depends on maternal consumption patterns and household characteristics.

Early determinants of obesity: genetic, epigenetic, and in utero influences

There is an emerging body of work indicating that genes, epigenetics, and the in utero environment can impact whether or not a child is obese. While certain genes have been identified that increase one's risk for becoming obese, other factors such as excess gestational weight gain, gestational diabetes mellitus, and smoking can also influence this risk. Understanding these influences can help to inform which behaviors and exposures should be targeted if we are to decrease the prevalence of obesity. By helping parents and young children change certain behaviors and exposures during critical time periods, we may be able to alter or modify one's genetic predisposition. However, further research is needed to determine which efforts are effective at decreasing the incidence of obesity and to develop new methods of prevention. In this paper, we will discuss how genes, epigenetics, and in utero influences affect the development of obesity. We will then discuss current efforts to alter these influences and suggest future directions for this work.

Educational inequalities in perinatal outcomes: the mediating effect of smoking and environmental tobacco exposure

OBJECTIVE

Socioeconomic status (SES) is adversely associated with perinatal outcomes. This association is likely to be mediated by tobacco exposure. However, previous studies were limited to single perinatal outcomes and devoted no attention to environmental tobacco exposure. Therefore, this study aimed firstly to explain the role of maternal smoking in the association between maternal education and preterm birth (PTB), low birth weight (LBW) and small for gestational age (SGA), and secondly to explain whether environmental tobacco smoke mediates these associations further.

STUDY DESIGN

This study was nested in a population-based cohort study in the Netherlands, the Amsterdam Born Children and their Development (ABCD) study. Analyses were done in a sample of 3821 pregnant women of Dutch origin, using logistic regression analysis.

RESULTS

Least educated women, who were more often smoking and exposed to environmental tobacco smoke, had a significantly higher risk of PTB (OR 1.95 [95% CI: 1.19-3.20]), LBW (OR 2.41 [95% CI: 1.36-4.27]) and SGA (OR 1.90 [95% CI 1.32-2.74]) than highly educated women. The mediating effect of smoking in the least educated women was 43% for PTB, 55% for LBW and 66% for SGA. Environmental tobacco smoke did not explain these associations further. After adjustment for maternal smoking, the association between lower maternal education and pregnancy outcomes was no longer significant.

CONCLUSIONS

Smoking explains to a considerable extent the association between lower maternal education and adverse perinatal outcomes. Therefore, tobacco-interventions in lower educated women should be primarily focussed on maternal smoking to reduce PTB, LBW, and SGA. Additional attention to environmental tobacco exposure does not seem to reduce educational inequalities in perinatal outcomes.

Determinants of rapid weight gain during infancy: baseline results from the NOURISH randomised controlled trial

Background

Rapid weight gain in infancy is an important predictor of obesity in later childhood. Our aim was to determine which modifiable variables are associated with rapid weight gain in early life.

Methods

Subjects were healthy infants enrolled in NOURISH, a randomised, controlled trial evaluating an intervention to promote positive early feeding practices. This analysis used the birth and baseline data for NOURISH. Birthweight was collected from hospital records and infants were also weighed at baseline assessment when they were aged 4-7 months and before randomisation. Infant feeding practices and demographic variables were collected from the mother using a self administered questionnaire. Rapid weight gain was defined as an increase in weight-for-age Z-score (using WHO standards) above 0.67 SD from birth to baseline assessment, which is interpreted clinically as crossing centile lines on a growth chart. Variables associated with rapid weight gain were evaluated using a multivariable logistic regression model.

Results

Complete data were available for 612 infants (88% of the total sample recruited) with a mean (SD) age of 4.3 (1.0) months at baseline assessment. After adjusting for mother's age, smoking in pregnancy, BMI, and education and infant birthweight, age, gender and introduction of solid foods, the only two modifiable factors associated with rapid weight gain to attain statistical significance were formula feeding [OR = 1.72 (95%CI 1.01-2.94), P = 0.047] and feeding on schedule [OR = 2.29 (95%CI 1.14-4.61), P = 0.020]. Male gender and lower birthweight were non-modifiable factors associated with rapid weight gain.

Conclusions

This analysis supports the contention that there is an association between formula feeding, feeding to schedule and weight gain in the first months of life. Mechanisms may include the actual content of formula milk (e.g. higher protein intake) or differences in feeding styles, such as feeding to schedule, which increase the risk of overfeeding.

Trial Registration

Australian Clinical Trials Registry ACTRN12608000056392

Aortic intima-media thickness in nicotine-exposed rat pups during gestation and lactation period

There have been several studies confirming an association between maternal smoking during pregnancy and low birth weight. The detrimental effect of nicotine exposure beginning in fetal life continues during lactation, in infancy and in the early childhood period. In our previous studies, we found increased aortic intima-media thickness (aIMT) as a preatherosclerotic lesion in neonates with intrauterine growth restriction and in infants of smoking mothers. We aimed to evaluate histopathologically the effect of nicotine exposure during pregnancy and lactation period on fetal growth and aIMT at postnatal 45 days of age (end of the mid-adolescent period) in rat pups living in the same conditions. Gravid rats were assigned into three groups. In nicotine A, pregnant rats received 6 mg/kg/day nicotine intraperitoneally during pregnancy from 1 to 21 days of gestation and lactation (until postnatal day 21). Nicotine B received 3 mg/kg/day nicotine for the same period. Control pregnant rats received only saline intraperitoneally. Abdominal aIMT was studied histopathologically at postnatal 45 days of age. Nicotine exposure resulted in decreased birth weight and pregnancy weight gain. The mean aIMT values of the rat pups exposed to nicotine in both nicotine A and B groups were higher than those of the control group (103.78 ± 21.33 μm, 99.11 ± 30.12 μm, and 62.56 ± 7.18 μm, respectively). In conclusion, the detrimental effect on birth weight of nicotine exposure that began in fetal life is dose dependent. Nicotine exposure during intrauterine life and the lactation period causes increased aIMT in rat pups.

Effect of prenatal tobacco smoke exposure on fetal growth potential

AIM

to determine the independent effect of prenatal tobacco smoke exposure on fetal growth using customized birthweight norms.

METHODS

demographic characteristics and data on exposure to tobacco smoke during pregnancy were obtained from singleton neonates ≥ 34 weeks' gestation. Centile Calculator software v62.2 (www.gestation.net) was used for calculating customized birthweight percentiles.

RESULTS

of the 3227 neonates studied, 30.9% were exposed to maternal smoking during pregnancy, whereas involuntary maternal exposure was reported in 20.1%. Growth restriction was noted in 350 (10.8%). The odds ratio (OR) for fetal growth restriction was 1.49 (1.10-1.91) in passive smokers, and 2.34 (1.81-2.96) in smokers. A decrease in birthweight and an increase in the prevalence of growth restriction with the increasing number of cigarette consumption was observed. This effect was evident even in cases of a "minimal" consumption of 1-5 cigarettes per day.

CONCLUSION

an essential adverse effect of tobacco smoke exposure on fetal growth in pregnancies exposed to passive smoking, as well as in those with "minimal" maternal cigarette consumption, was found. Since approximately 30% of growth restricted neonates could be independently attributed to active or passive maternal exposure, these findings reinforce the need for smoking preventive strategies in pregnant women and their environment.

In utero tobacco exposure epigenetically modifies placental CYP1A1 expression

The metabolic pathways used by higher-eukaryotic organisms to deal with potentially carcinogenic xenobiotic compounds from tobacco smoke have been well characterized. Carcinogenic compounds such as polycyclic aromatic hydrocarbons are metabolized sequentially in 2 phases: in phase I, CYP1A1 catalyzes conversion into harmful hydrophilic DNA adducts, whereas in phase II, GSTT1 enables excretion via conjugation into polar electrophiles. In an effort to understand susceptibility to in utero tobacco exposure, we previously characterized known metabolic functional polymorphisms and demonstrated that although deletion of fetal GSTT1 significantly modified birth weight in smokers, no polymorphism fully accounted for fetal growth restriction. Because smoking up-regulates CYP1A1 expression, we hypothesized that nonallelic (epigenetic) dysregulation of placental CYP1A1 expression via alterations in DNA methylation (meCpG) may further modify fetal growth. In the present article, we compared placental expression of multiple CYP family members among gravidae and observed significantly increased CYP1A1 expression among smokers relative to controls (4.4-fold, P < .05). To fully characterize CYP1A1 meCpG status, bisulfite modification and sequencing of the entire proximal 1-kilobase promoter (containing 59 CpG sites) were performed. CpG sites immediately proximal to the 5′-xenobiotic response element transcription factor binding element were significantly hypomethylated among smokers (55.6% vs 45.9% meCpG, P = .027), a finding that uniquely correlated with placental gene expression (r = 0.737, P = .007). Thus, in utero tobacco exposure significantly increases placental CYP1A1 expression in association with differential methylation at a critical xenobiotic response element.

Partner violence during pregnancy: prevalence, effects, screening, and management

The purpose of this review is to provide an overview of the current state of knowledge regarding the experience of intimate partner violence (IPV) during pregnancy. Pregnancy IPV is a significant problem worldwide, with rates varying significantly by country and maternal risk factors. Pregnancy IPV is associated with adverse newborn outcomes, including low birth weight and preterm birth. Many mechanisms for how IPV may impact birth outcomes have been proposed and include direct health, mental health, and behavioral effects, which all may interact. Screening for IPV during pregnancy is essential, yet due to time constraints and few clear recommendations for assessment, many prenatal providers do not routinely inquire about IPV, or even believe they should. More training is needed to assist health care providers in identifying and managing pregnancy IPV, with additional research needed to inform effective interventions to reduce the rates of pregnancy IPV and resultant outcomes.

Pharmacogenomics of maternal tobacco use: metabolic gene polymorphisms and risk of adverse pregnancy outcomes

OBJECTIVE

To assess whether functional maternal or fetal genotypes along well-characterized metabolic pathways (ie, CYP1A1, GSTT1, and CYP2A6) may account for varying associations with adverse outcomes among pregnant women who smoke.

METHODS

DNA samples from 502 smokers and their conceptuses, alongside women in a control group, were genotyped for known functional allelic variants of CYP1A1 (Ile462Val AA>AG/GG), GSTT1(del), and CYP2A6 (Lys160His T>A). Modification of the association between smoking and outcome by genotype was evaluated. Outcomes included birth weight, pregnancy loss, preterm birth, small for gestational age, and a composite outcome composed of the latter four components plus abruption.

RESULTS

No interaction between maternal or fetal genotype of any of the polymorphisms and smoking could be demonstrated. In contrast, the association of smoking with gestational age-adjusted birth weight (birth weight ratio) was modified by fetal GSTT1 genotype (P for interaction=.02). Fetuses with GSTT1(del) had a mean birth weight reduction among smokers of 262 g (P=.01), whereas in fetuses without the GSTT1(del) the effect of tobacco exposure was nonsignificant (mean reduction 87 g, P=.16). After adjusting for confounding, results were similar.

CONCLUSION

Fetal GSTT1 deletion significantly and specifically modifies the effect of smoking on gestational age-corrected birth weight.

Prediction of birth weight by cotinine levels during pregnancy in a population of black smokers

OBJECTIVE

The goal was to investigate the association between maternal salivary cotinine levels (SCLs) and pregnancy outcomes among black smokers.

METHODS

In a randomized, controlled trial conducted in 2001-2004 in Washington, DC, 714 women (126 active smokers [18%]) were tested for SCLs at the time of recruitment and later in pregnancy. Sociodemographic health risks and pregnancy outcomes were recorded.

RESULTS

Birth weights were significantly lower for infants born to mothers with baseline SCLs of > or =20 ng/mL in comparison with <20 ng/mL (P = .024), > or =50 ng/mL in comparison with <50 ng/mL (P = .002), and > or =100 ng/mL in comparison with <100 ng/mL (P = .002), in bivariate analyses. In linear regression analyses adjusting for sociodemographic and medical factors, SCLs of > or =20 ng/mL were associated with a reduction in birth weight of 88 g when SCLs were measured at baseline (P = .042) and 205 g when SCLs were measured immediately before delivery (P < .001). Corresponding results were 129 g (P = .006) and 202 g (P < .001) for > or =50 ng/mL and 139 g (P = .007) and 205 g (P < .001) for > or =100 ng/mL. Gestational age was not affected significantly at any SCL, regardless of when SCLs were measured.

CONCLUSIONS

Elevated SCLs early in pregnancy or before delivery were associated with reductions in birth weight. At any cutoff level, birth weight reduction was more significant for the same SCL measured in late pregnancy. Maintaining lower levels of smoking for women who are unable to quit may be beneficial.

Environmental influences on epigenetic profiles

Studies of environmental challenges, such as hazardous air pollutants, nonmutagenic toxins, diet choice, and maternal behavioral patterns, reveal changes in gene expression patterns, DNA methylation, and histone modifications that are in causal association with exogenous exposures. In this article we summarize some of the recent advances in the field of environmental epigenetics and highlight seminal studies that implicate in utero exposures as causative agents in altering not only the epigenome of the exposed gestation, but that of subsequent generations. Current studies of the effects of maternal behavior, exposure to environmental toxins, and exposure to maternal diet and an altered gestational milieu are summarized.

Relationships between prenatal smoking cessation, gestational weight gain and maternal lifestyle characteristics

OBJECTIVES

To describe maternal characteristics and lifestyle factors associated with prenatal smoking habits and to appraise the effect of quitting smoking in early gestation on maternal weight gain during pregnancy.

METHODS

This is a follow-up study of 1753 women who gave birth in 1984/1985 in Stockholm, Sweden. Multivariate logistic models were used to evaluate the association between smoking cessation and weight gain above the American Institute of Medicine (IOM) recommendations, based on pre-pregnancy BMI.

RESULTS

About 22% of all participants identified themselves as current smokers and 11.6% reported smoking cessation during pregnancy. Smokers were more likely to be single mothers and reported low quality of breakfast (e.g. eating only 1 food group at breakfast). Non-smokers were older, more likely to be married and have a healthier lifestyle. Quitters also adopted healthier eating habits (e.g. improvement in their breakfast quality). Women who quit smoking gained, on average, 15.3 kg (SD 4.4) during pregnancy, non-smokers gained 14.1 kg (SD 4.0) and smokers gained 13.8 kg (SD 4.3). Quitters gained significantly more weight than both non-smokers and smokers (p<0.001). Smoking cessation was significantly associated with gaining weight above IOM recommendations, even after controlling for potential confounders (OR: 2.0; 95%CI: 1.4-3.0; p<or=0.0001).

CONCLUSIONS

In this population, smoking cessation in early pregnancy doubled the likelihood of gaining excess weight. This finding highlights the need for supportive measures to help control weight gain among women who quit smoking during pregnancy.

In utero tobacco exposure: the effects of heavy and very heavy smoking on the rate of SGA infants in the Federal State of Saarland, Germany

OBJECTIVE

To assess the effects of heavy and very heavy smoking on the rate of small for gestational age (SGA) infants, and to assess socio-economic and regional differences in smoking patterns in pregnant women in Germany.

STUDY DESIGN

The Neonatal and Perinatal database of the federal state of Saarland, Germany was used to perform a population-based analysis of preterm (>32 weeks of gestation) and term (>36 weeks of gestation) newborns in 2004-2006. The rate of SGA babies dependent on the amount of tobacco exposure among self-identified smokers and non-smokers were assessed, and distinct maternal risk factors for smoking were evaluated. Our data were compared with the German National Perinatal database.

RESULTS

14,593 paired data sets (peripartum/perinatal) were included in this study. The overall rate of smoking during pregnancy was 11.8% with a high percentage of pregnant women smoking 11-20 cigarettes/day (heavy smoker; 4.0%), and >20 cigarettes/day (very heavy smoker; 0.6%). Self-identified heavy tobacco use significantly increased the risk for SGA infants (p<0.01) in women without uteroplacental insufficiency. Risk factors for smoking included ethnicity (German/Caucasian), socio-economic parameters (single vs. non-single households, status of employment) and age. Smoking pattern and the rate of SGA babies in our cohort differed substantially from the national average.

CONCLUSIONS

Although the overall rate of smoking appears comparable to previously published data, heavy and very heavy smoking was high in our cohort. Heavy smoking was disproportionately associated with SGA. Preventative measures and strategies should take into consideration socio-economic risk factors as well as regional differences, and should be targeted at distinct subgroups that are especially prone to smoking during pregnancy.

Spontaneous preterm birth and small for gestational age infants in women who stop smoking early in pregnancy: prospective cohort study

OBJECTIVES

To compare pregnancy outcomes between women who stopped smoking in early pregnancy and those who either did not smoke in pregnancy or continued to smoke.

DESIGN

Prospective cohort study.

SETTING

Auckland, New Zealand and Adelaide, Australia.

PARTICIPANTS

2504 nulliparous women participating in the Screening for Pregnancy Endpoints (SCOPE) study grouped by maternal smoking status at 15 (+/-1) week's gestation.

MAIN OUTCOME MEASURES

Spontaneous preterm birth and small for gestational age infants (birth weight <10th customised centile). We compared odds of these outcomes between stopped smokers and non-smokers, and between current smokers and stopped smokers, using logistic regression, adjusting for demographic and clinical risk factors.

RESULTS

80% (n=1992) of women were non-smokers, 10% (n=261) had stopped smoking, and 10% (n=251) were current smokers. We noted no differences in rates of spontaneous preterm birth (4%, n=88 v 4%, n=10; adjusted odds ratio 1.03, 95% confidence interval l0.49 to 2.18; P=0.66) or small for gestational age infants (10%, n=195 v 10%, n=27; 1.06, 0.67 to 1.68; P=0.8) between non-smokers and stopped smokers. Current smokers had higher rates of spontaneous preterm birth (10%, n=25 v 4%, n=10; 3.21, 1.42 to 7.23; P=0.006) and small for gestational age infants (17%, n=42 v 10%, n=27; 1.76, 1.03 to 3.02; P=0.03) than stopped smokers.

CONCLUSION

In women who stopped smoking before 15 weeks' gestation, rates of spontaneous preterm birth and small for gestational age infants did not differ from those in non-smokers, indicating that these severe adverse effects of smoking may be reversible if smoking is stopped early in pregnancy.

Maternal smoking in pregnancy and externalizing behavior in 18-month-old children: results from a population-based prospective study

OBJECTIVE

The relation between prenatal smoking and child behavioral problems has been investigated in children of school age and older, but prospective studies in younger children are lacking. Using the population-based prospective Norwegian Mother and Child Cohort Study, we examined the risk for externalizing behaviors among 18-month-old children after exposure to maternal smoking during pregnancy.

METHOD

Participants were 22,545 mothers and their 18-month-old children. Mothers reported their smoking habits at the 17th week of gestation and their child's externalizing behavior at 18 months of age by means of standardized questionnaires. Data were analyzed using logistic regression, with scores of externalizing behavior above the 88.6th percentile as the dependent variable and self-reported smoking as the independent variable. We examined the child's sex as a possible moderator.

RESULTS

We documented a threshold effect of smoking 10 cigarettes or more per day during pregnancy on subsequent externalizing behaviors among 18-month-old children, even after adjusting for relevant confounders (odds ratio 1.32, 95% confidence interval 1.03-1.70). The child's sex did not moderate these effects (odds ratio 0.98, 95% confidence interval 0.83-1.16).

CONCLUSIONS

Maternal smoking during pregnancy increases offspring's subsequent risk for externalizing behavior problems at 18 months of age. The pattern of risk does not differ between boys and girls. Our findings suggest a population attributable risk of 1.75% [corrected] (i.e., the proportion of externalizing cases that could potentially be avoided if prenatal smoking was eliminated or reduced to fewer than 10 cigarettes per day).

Maternal smoking and congenital heart defects

OBJECTIVES

In a population-based case-control study, we investigated the association between congenital heart defects and maternal smoking.

METHODS

The National Birth Defects Prevention Study enrolled 3067 infants with nonsyndromic congenital heart defects and their parents and 3947 infants without birth defects and their parents. Affected infants had > or = 1 of the following defects: conotruncal, septal, anomalous pulmonary venous return, atrioventricular septal defects, and left-sided or right-sided obstructive heart defects. Mothers of case and control infants were asked if they smoked during the periconceptional period, defined as 1 month before pregnancy through the first trimester. Maternal home and workplace exposure to tobacco smoke during the same period was also determined. Logistic regression was used to compute odds ratios and 95% confidence intervals while controlling for potential confounders.

RESULTS

Case infants were more likely to be premature and have lower birth weight than control infants. Women who smoked anytime during the month before pregnancy to the end of the first trimester were more likely to have infants with septal heart defects than women who did not smoke during this time period. This association was stronger for mothers who reported heavier smoking during this period. This relation was independent of potential confounding factors, including prenatal vitamin use, alcohol intake, maternal age, and race or ethnicity. Women who smoked > or = 25 cigarettes per day were more likely than nonsmoking mothers to have infants with right-sided obstructive defects. There was no increased risk of congenital heart defects with maternal exposure to environmental tobacco smoke.

CONCLUSIONS

Maternal smoking during pregnancy was associated with septal and right-sided obstructive defects. Additional investigation into the timing of tobacco exposure and genetic susceptibilities that could modify this risk will provide a more precise evidence base on which to build clinical and public health primary prevention strategies.

[Obstetrical risk factors for low birth-weight in a rural Sahelian area]

The objective of this study is to identify the obstetrical risk factors related to low birth-weight in a rural environment in the Sahel region. A cross-sectional study carried out between January 1st and December 31st, 2003, recorded and registered 1013 new born children (from full-term pregnancies) from the north-central part of Burkina Faso. The adjusted odds for ratios of low birth-weight were estimated for each obstetric and pregnancy characteristic through a multiple level logic regression analysis. After adjustment for socioeconomic variables, the following were noted as significant factors which seriously increased the risk of low birth-weight: first time pregnancy (OR = 2.8), severe vomiting (OR = 3.4), heavy housework (OR = 1.6), and agricultural labour (OR = 3.3). The existence of high risk was also present in case of women giving birth at home without any medical assistance (OR = 2.1). The number of prenatal visits does not indicate or confer any direct link to prevention of risks or positive benefit on birth-weight status. In light of these results, it is necessary to redefine the content and the procedures for pregnancy surveillance and care, including and adequate management of severe vomiting and increased public awareness on reduction of house work and manual labour for pregnant women.

In utero tobacco exposure is associated with modified effects of maternal factors on fetal growth

OBJECTIVE

The objective of the study was to evaluate whether maternal tobacco use is associated with an attenuation in fetal birthweight among women with nutritional and uteroplacental constraints.

STUDY DESIGN

A population-based retrospective analysis of term (37 weeks or longer) singleton pregnancies delivered in Utah from 1991 to 2001. Birthweight (BW) and percent small for gestational age (SGA) (less than 10% for gestational age) among self-identified smokers and nonsmokers were compared. Adjusted odds ratios (ORs) were calculated to measure the association of maternal smoking with delivery of an SGA infant controlling for potential confounders across maternal strata.

RESULTS

Among the 424,912 gestations, 37,076 occurred in self-identified smokers. Mean BW was significantly less and the prevalence of SGA infants was significantly greater in tobacco-exposed infants across all maternal BMI strata (P < .001) as well as pregnancies complicated by diabetes (P < .001) and hypertensive disorders (P < .001). In a multivariable logistic regression model, tobacco exposure remained the significant associative factor for SGA (OR 3.53, 95% confidence interval 2.61 to 4.79) after selecting for the first birth in the study interval (n = 283,916).

CONCLUSION

Self-identified tobacco use increases the risk of a SGA infant at term across maternal strata.

Pre-pregnancy body mass index, gestational weight gain, and other maternal characteristics in relation to infant birth weight

OBJECTIVES

Infant birth weight is influenced by modifiable maternal pre-pregnancy behaviors and characteristics. We evaluated the relationship among pre-pregnancy body mass index (BMI), gestational weight gain, and infant birth weight, in a prospective cohort study.

METHODS

Women were enrolled at < or =20 weeks gestation, completed in-person interviews and had their medical records reviewed after delivery. Infant birth weight was first analyzed as a continuous variable, and then grouped into Low birth weight (LBW) (<2,500 g), normal birth weight (2,500-3,999 g), and macrosomia (> or =4,000 g) in categorical analysis. Pre-pregnancy BMI and gestational weight gain were categorized based on Institute of Medicine BMI groups and gestational weight gain guidelines. Associations among infant birth weight and pre-pregnancy BMI, gestational weight gain, and other factors were evaluated using multivariate regression. Risk ratios were estimated using generalized linear modeling procedures.

RESULTS

Pre-pregnancy BMI was independently and positively associated with infant birth weight (beta = 44.7, P = 0.001) after adjusting for confounders, in a quadratic model. Gestational weight gain was positively associated with infant birth weight (beta = 19.5, P < 0.001). Lower infant birth weight was associated with preterm birth (beta = -965.4, P < 0.001), nulliparity (beta = -48.6, P = 0.015), and female babies (beta = -168.7, P < 0.001). Less than median gestational weight gain was associated with twice the risk of LBW (RR = 2.04, 95% CI 1.34-3.11). Risk of macrosomia increased with increasing pre-pregnancy BMI and gestational weight gain (P for linear trend <0.001).

CONCLUSIONS

These findings support the need to balance pre-pregnancy weight and gestational weight gain against the risk of LBW and macrosomia among lean and obese women, respectively.

Prenatal weight gain following smoking cessation

OBJECTIVE

To evaluate the association of changes in smoking habit with maternal weight gain.

STUDY DESIGN

We questioned 4000 pregnant women > or =20 years about previous and current smoking habits during a second trimester visit to general prenatal clinics in 6 Brazilian cities, from 1991 to 1995, and followed their weight, through chart review, to term.

RESULTS

Of women who reported stopping smoking (915, 23% of the total), 240 (26.2%) stopped during pregnancy. The median number of cigarettes smoked/day among those who reported continued smoking (717, 18%) decreased from 10 to 5 with pregnancy. In linear regression models adjusting for age, educational attainment, ethnicity, prepregnancy body mass index, parity and clinical center, ex-smokers gained 1.03 kg (95%CI 0.59-1.46) more than those reporting never smoking, this difference being greater: 1.54 kg (95%CI 0.78-2.30) in those who reported quitting while pregnant. The size of weight gain in both continuing smokers and ex-smokers was proportional to the reduction in daily number of cigarettes smoked during pregnancy, being 0.38 kg (95%CI 0.07-0.68) greater for each 10 cigarettes reduced (p=0.007).

CONCLUSION

Decreasing the quantity of cigarettes smoked in pregnancy, although important for maternal and child health, is associated with maternal weight gain.

Cross-sectional study of weight gain and increase in BMI throughout pregnancy

OBJECTIVE

To generate reliable new reference ranges for weight gain and increase in body mass index (BMI) during pregnancy from a large population.

STUDY DESIGN

In a prospective cross-sectional study at the Obstetric outpatient clinic, Zurich University Hospital, weight gain and BMI, before gestation and at the booking visit, were determined in 4034 pregnant women with accurately dateable singleton pregnancies (Caucasian: N = 3242, Asian (predominantly from Sri Lanka, Thailand and the Philippines): N = 578 and Black: N = 214). Women with known insulin-dependent diabetes mellitus before pregnancy were excluded. Fifth, 50th and 95th centiles were presented for Caucasians and corresponding centile curves for Asians and Blacks. Simple and multiple regression analyses were performed for various risk factors. A significance level of P < 0.05 was used in all tests.

RESULTS

Mean weight gain was 15.5+/-5.9 kg (34.2+/-13.0 lb) at term with values >25.4 kg (56.0 lb) and <5.7 kg (12.6 lb) for the 95th and the 5th centile, respectively. Mean BMI increased slightly and steadily to 28 kgm(-2) at term. Parity and pre-pregnancy BMI were significant determinants in Caucasians. Weight gain and BMI was slightly lower in Asians and Blacks.

CONCLUSIONS

BMI centile curves have the advantage in that they consider height during the whole course of pregnancy. It may be an additional helpful tool in controlling weight gain in pregnancy. Further studies are required to determine the prognostic implications of values > or = 95th centile and < or = 5th centile.

Prepregnancy weight, inappropriate gestational weight gain, and smoking: Relationships to birth weight

This study was designed to test predictors of infant birth weight based on categories of prepregnancy body mass index (BMI), gestational weight gain, and smoking. Data were collected retrospectively from records of 233 mother-infant pairs enrolled in the Siouxland Women, Infants, and Children (WIC) Program in Sioux City, Iowa. Prepregnancy BMI and gestational weight gain were coded according to Institute of Medicine guidelines. Smoking behavior was coded based on reported smoking during the last 3 months of pregnancy. Multiple regression analysis was used to test predictors of infant birth weight. Forty-two percent of women gained more weight than recommended, and 16% gained less than recommended. Based on prepregnancy BMI, women were classified as underweight (12%), overweight (16%), or obese (31%). Twenty-four percent of mothers reported smoking late in gestation. Higher birth weight was predicted by prepregnancy obesity (+144 g). Lower infant birth weight was predicted by lower (-162 g) and higher (-153 g) than recommended weight gain, and by lower (-299 g) and higher (-168 g) levels of smoking. Depression of birth weight among women who gained excess weight may relate to inadequate early weight gain or pregnancy complications. More research is needed regarding physiological consequences of these maternal factors and their associated demographic risk factors.

Factors predicting birth weight in a low-risk sample: the role of modifiable pregnancy health behaviors

OBJECTIVES

The purpose of the present study was to examine background and modifiable pregnancy health behavior factors predicting infant birthweight in an economically and educationally disadvantaged sample with low medical risk.

METHODS

PARTICIPANTS were recruited from a family practice center in rural Appalachia.

PARTICIPANTS

Over 220, predominantly Caucasian and lower SES women with low risk pregnancies were included in the sample. Data were collected through systematic chart review. Half of the women smoked during pregnancy and over 10% gave birth to low birth weight (LBW; < 2500 g) babies.

RESULTS

Compared with those who gave birth to normal weight newborns, women with LBW babies had more miscarriages, but did not differ significantly on other background factors. Women who delivered LBW babies gained less weight during pregnancy and were more likely to smoke than remaining women. After control for background factors, modifiable pregnancy health behavior factors (weight gain, prenatal care, smoking, alcohol and substance use) accounted for over 11% of birth weight variance, with nearly 7% attributable solely to smoking.

CONCLUSIONS

Pregnancy smoking was the strongest behavioral predictor of LBW in this economically and educationally disadvantaged rural sample, suggesting that efforts to reduce LBW in similar populations should include targeting pregnancy smoking.

Combined effects of maternal smoking status and dietary intake related to weight gain and birth size parameters

OBJECTIVE

To investigate the interaction of smoking status and dietary intake during pregnancy and its relationship to maternal weight gain and birth size parameters.

DESIGN

An observational prospective study.

SETTING

Free-living conditions.

POPULATION

Four hundred and eight healthy pregnant Icelandic women.

METHODS

Maternal smoking status, lifestyle factors and dietary habits were evaluated with questionnaires. Intake of foods and supplements was also estimated with a semiquantitative food frequency questionnaire for the previous 3 months. All questionnaires were filled out between 11 and 15 weeks and between 34 and 37 weeks of gestation. Smoking status in relation to optimal and/or excessive weight gain during pregnancy was represented with logistic regression controlling for potential confounding factors.

MAIN OUTCOME MEASURES

Maternal weight gain, smoking status, dietary intake and birthweight.

RESULTS

Women who smoked throughout pregnancy were unlikely to gain optimal weight or more (OR 0.51, 95% CI 0.27-0.97), whereas smoking cessation in connection with pregnancy ('former smokers') doubled the risk of excessive weight gain (OR 2.03, 95% CI 1.24-3.35). The latter association was no longer significant after adjustment for dietary factors and other confounding factors. Former smokers ate the least amount of fruit and vegetables (fruit: 129 versus 180 and 144 g/day (median), P= 0.038; vegetables: 53 versus 76 and 72 g/day, P= 0.026 for former smokers, nonsmokers and smokers, respectively). Birthweight was lowest among infants born to smokers, but birthweight was similar for former smokers and nonsmokers (3583 +/- 491 g versus 3791 +/- 461 g and 3826 +/- 466 g, respectively; P= 0.003).

CONCLUSIONS

Smoking cessation in early pregnancy or pre-pregnancy is not associated with low birthweight. It is, however, associated with excessive maternal weight gain and a low fruit and vegetable intake.

Low birthweight and asthma among young urban children

OBJECTIVES

We assessed whether the association between low birthweight and early childhood asthma can be explained by an extensive set of individual- and neighborhood-level measures.

METHODS

A population-based sample of children born in large US cities during 1998-2000 was followed from birth to age 3 years (N=1803). Associations between low birthweight and asthma diagnosis at age 3 years were estimated using multilevel models. Prenatal medical risk factors and behaviors, demographic and socioeconomic characteristics, and neighborhood characteristics were controlled.

RESULTS

Low-birthweight children were twice as likely as normal birthweight children to have an asthma diagnosis (34% vs 18%). The fully adjusted association (OR= 2.36; P<.001) was very similar to the unadjusted association (OR= 2.48; P<.001). Rates of renter-occupied housing and vacancies at the census tract-level were strong independent predictors of childhood asthma.

CONCLUSIONS

Very little of the association between low birthweight and asthma at age 3 can be explained by an extensive set of demographic, socioeconomic, medical, behavioral, and neighborhood characteristics. Associations between neighborhood housing characteristics and asthma diagnosis in early childhood need to be further explored.

Socio-economic status, smoking during pregnancy and birth outcomes: an analysis of cross-sectional community studies in Liverpool (1993-2001)

OBJECTIVE

To assess the influence of socio-economic status on pregnancy outcomes in smoking mothers.

STUDY DESIGN

Retrospective analysis.

METHODS

Parent-completed questionnaires addressing pregnancy smoking patterns and birth outcomes. Were distributed via children aged 5-11 years attending 10 primary schools in Merseyside. Data from three community-based cross-sectional surveys undertaken in 1993, 1998 and 2001 were analysed. Townsend score was used as an indicator of household socioeconomic status.

RESULTS

82.2 percent (n = 3730) of respondents were classified as low (disadvantaged) socio-economic status. One-third of mothers smoked during pregnancy and this proportion was significantly higher among disadvantaged than advantaged categories (37.7% versus 14.6%; p < 0.001). The logistic regression analysis showed that only maternal smoking during pregnancy was a significant risk factor for adverse birth outcomes when socioeconomic variables were controlled.

CONCLUSION

Birth outcomes were worse in babies of smoking mothers during pregnancy independent of household's socio-economic status.

Relationship between dietary intake of cod liver oil in early pregnancy and birthweight

OBJECTIVE

To investigate the possible association between birth outcome and marine food and cod liver oil intake of healthy women in early (prior to 15 weeks of gestation) pregnancy.

DESIGN

An observational study.

SETTING

Free-living conditions in a community with traditional fish and cod liver oil consumption.

POPULATION

Four hundred and thirty-five healthy pregnant Icelandic women without antenatal and intrapartum complications.

METHODS

Dietary intake of the women was estimated with a semi-quantitative food frequency questionnaire (FFQ) covering food intake together with lifestyle factors for the previous three months. Questionnaires were filled out at between 11 and 15 weeks and between 34 and 37 weeks of gestation. The estimated intake of marine food and cod liver oil was compared with birthweight by linear and logistic regression controlling for potential confounding.

MAIN OUTCOME MEASURES

Birthweight, cod liver oil intake, lifestyle factors (alcohol, smoking).

RESULTS

Fourteen percent of the study population used liquid cod liver oil in early pregnancy. Regression analysis shows that these women gave birth to heavier babies (P < 0.001), even after adjusting for the length of gestation and other confounding.

CONCLUSIONS

Maternal intake of liquid cod liver oil early in pregnancy was associated with a higher birthweight. Higher birthweight has been associated with a lower risk of diseases later in life and maternal cod liver oil intake might be one of the means for achieving higher birthweight.

Intrauterine growth retardation in full-term newborn infants with birth weights greater than 2,500 g

Intrauterine growth retardation (IUGR) is an overlooked problem in full-term infants with birth weights greater than 2,500 g. Birth weight less than the 10th percentile underestimates the presence of IUGR. The purpose of this study was to determine the prevalence of IUGR in full-term infants and to identify sociodemographic and maternal characteristics associated with IUGR. The Ohio Department of Health Vital Statistics database was used to obtain data related to sociodemographic and maternal characteristics. The fetal growth ratio (FGR) was used to determine the presence of IUGR. The sample consisted of 1,569 infants with normal ratios and 1,364 infants classified as IUGR. Infants with IUGR were more often male and African American or Asian American. Maternal characteristics associated with IUGR included history of smoking during pregnancy, lower pre-pregnancy weight, lower weight gain during pregnancy, and inadequate prenatal care. IUGR is present in a significant number of full-term infants with birth weights greater than 2,500 g. The long-term effects of IUGR in these infants remain to be determined.