Smoking during pregnancy: Missouri longitudinal study

Maternal smoking during pregnancy has been shown to be associated with reduced birthweight and increased fetal and infant mortality. This paper examines these patterns in first and second maternally-linked singleton pregnancies from 1978 to 1990 among 176 843 Missouri resident women with known smoking status in both pregnancies. Generally women were more likely to smoke in their second pregnancies (27.4%), than in their first (25.8%). This pattern was strongest among those whose first pregnancies occurred as teenagers, and for black women. The relationships of smoking during the first and second preg-nancies to outcomes in the second pregnancies were examined primarily through multivariate logistic regression. The adjusted relative risk (RR) of low birthweight (<2500 g) in the second pregnancy to not smoking in either pregnancy was 1.82 for those who smoked during the second pregnancy only, and 1.87 for those who smoked in both pregnancies. For those who smoked in the first pregnancy only, the RR was 0.97, not significantly different from 1. Adjusted smoking RRs for small-for-gestational age were larger, while adjusted RRs for fetal and neonatal mortality were smaller than the smoking RRs for low birthweight.     

Low birthweight at term and the timing of fetal exposure to maternal smoking.

OBJECTIVES. This study was undertaken to evaluate the risk of small-for-gestational-age birth for women who stop smoking or begin to smoke during pregnancy. METHODS. Women with term singleton pregnancies from a hospital-based cohort of 11,177 were classified as (1) nonsmokers; (2) smoked throughout pregnancy; (3) smoked during first trimester only; (4) smoked during first and second trimesters only; and (5) smoked during second and third trimesters or during third trimester only. Risk of small-for-gestational-age birth according to smoking category was estimated and adjusted for confounding factors by logistic regression. RESULTS. Women who stopped smoking by the third trimester were not at increased risk of small-for-gestational-age birth compared with nonsmokers. Women who began smoking during the second or third trimester had an elevated risk of small-for-gestational-age birth (odds ratio [OR] = 1.83; 95% confidence interval [CI] = 1.25, 2.67) similar to that for women who smoked throughout pregnancy (OR = 2.20; 95% CI = 1.90, 2.54). Risk of small-for-gestational-age birth increased with the number of cigarettes smoked during the third trimester. CONCLUSIONS. It is during the third trimester that smoking retards fetal growth, presenting a compelling opportunity for smoking cessation interventions. Programs must emphasize the importance of not resuming smoking late in pregnancy.     

Influence of maternal smoking on placental abruption in successive pregnancies: a population-based prospective cohort study in Sweden

The authors examined associations between cumulative smoking during a woman's first and second pregnancies and risk of placental abruption in the second pregnancy. They performed a population-based prospective cohort study of 526,690 women who delivered their first two consecutive singletons in Sweden in 1983-2001. Using logistic regression models, the authors found that, among women without placental abruption in the first pregnancy, smoking was associated with increased risk of abruption in the second pregnancy; however, this effect was confined to exposure occurring during the second pregnancy (adjusted odds ratio (OR)=1.8, 95% confidence interval (CI): 1.4, 2.3) but not the first (adjusted OR=1.1, 95% CI: 0.9, 1.3). Among women with a prior abruption, the risk of repeating abruption was increased irrespective of smoking habits. When women smoked during both pregnancies, there was an almost 11-fold increase in risk (adjusted OR=10.9, 95% CI: 7.3, 16.3). These findings suggest that women who quit smoking before pregnancy may benefit from reduced risk of abruption. The observation that the recurrence of abruption is substantially increased regardless of changes in smoking habits suggests that factors other than smoking may influence the recurrence of placental abruption.     

Influence of maternal active and passive smoking during pregnancy on birthweight in newborns

Many studies have documented a strong association of active smoking during pregnancy with fetal growth retardation. Increasing interest has also been focused on whether there is an association between exposure of pregnant women to environmental tobacco smoke (ETS) and low birthweight of their babies. In the intervention controlled study "Healthy Pregnancy--Healthy Child", mothers after delivery were interviewed by medical students who collected data about their smoking and nutrition. Students were also trained to stimulate non-smoking behaviour and to explain the risks related to smoking and exposure to ETS. Data from 1147 mothers after delivery were collected but only single births were included in the analysis of birthweight. In our study, 63.4% women never smoked and 32.2% women reported they had stopped smoking either before pregnancy or during the first trimester. Only 4.4% of mothers (n = 50) smoked during the whole pregnancy. Women with the history of smoking were exposed to ETS more often than mothers who never smoked (51.6% vs 17.4%; p < 0.001). The number of heavily exposed both at home and workplaces was more than twice higher among former smokers compared with never smokers (22.4% versus 9.4%, p < 0.01). The average birthweight of babies born to women who had stopped smoking was higher than that born to never smokers. The average birthweight of babies born to women who smoked during pregnancy was lower by 119 g and 171 g than that of the babies born to never smokers and former smokers, respectively. When pre-term neonates were excluded, differences in birthweight between babies born to never smokers and either formerly smoking or still smoking mothers were slightly lower. The greatest effect of ETS exposure on birthweight was recorded in never smoking mothers; an average reduction in birthweight was 88 g. A strong dose-effect was observed; in mothers heavily exposed to ETS both at home and at work, the babies' birthweight was lower by 189 g in comparison with the group of non-exposed, never smoking mothers and even by 70 g compared with mothers smoking during pregnancy.     

Prenatal Smoking in Two Consecutive Pregnancies: Georgia, 1989–1992

Objective: To explore the patterns of prenatal smoking among women whose first and second pregnancies ended in live births. Methods: We used population-based data to explore prenatal smoking among 14,732 white and 8968 black Georgia residents whose first and second pregnancies ended in live births during 1989–1992. Smoking status was obtained from birth certificates linked for individual mothers. Because of demographic differences, we analyzed white and black women separately. Results: Approximately 15% (2253) of white women and 4% (318) of black women smoked during their first pregnancy. Of those smokers, 69% (1551) of white women and 58% (184) of black women also smoked during their second pregnancy. For both white and black nonsmokers during the first pregnancy, low education was the most significant predictor of smoking during the second pregnancy, after adjusting for consistency of the father's name on the birth certificate, prenatal care, birth interval, mother's county of residence, and birth outcome. Conclusions: The prevalence of smoking in this study may be low because of underreporting of prenatal smoking on birth certificates. The majority of women who smoked during their first pregnancy also smoked during their second, suggesting that these women exposed their first infant to tobacco smoke both in utero and after delivery. Practitioners should offer smoking cessation programs to women during, as well as after, pregnancy. Pediatricians should educate parents on the health risks to young children of exposure to environmental tobacco smoke and refer smoking parents to smoking cessation programs.     

Adolescent smoking in pregnancy and birth outcomes

INTRODUCTION: Cigarette smoking amongst pregnant adolescents is a preventable risk factor associated with low birthweight (<2,500 g), preterm birth (<37 weeks) and infant mortality. The aim of this study was to compare birth outcomes of adolescents who smoke during pregnancy with those who do not and to construct their birthweight-for-gestational-age curves. METHODS: A retrospective cohort analysis of 534 adolescents (10 cigarettes daily had babies with larger birthweight reduction (P = 0.001). CONCLUSION: Almost half of all adolescents smoked during their pregnancy. Birthweight-for-gestational-age curves of smoking adolescents showed a marked fall-off in weight from 36 weeks of gestation, and at least 10% of adolescent smokers showed fetal growth restriction from before 32 weeks of gestation.     

Prenatal exposure to tobacco: I. Effects on physical growth at age three

The height and weight of 714 children whose mothers smoked at the beginning of their pregnancies were assessed at three years of age. The children of women who quit smoking during pregnancy were taller and heavier than those of women who continued to smoke throughout pregnancy. Adjustment for maternal postpartum smoking status reduced the difference in weight, but had little effect on height. The differences in both height and weight at three years of age were greatly reduced when adjusted for size at birth and length of gestation. These results suggest that deficits associated with maternal smoking are not overcome by three years of age and that at least some of the observed anthropometric deficits may be extensions of deficits in fetal growth.     

Maternal smoking during pregnancy and offspring IQ

BACKGROUND: Maternal smoking in pregnancy lowers birthweight. It is unclear, however, whether smoking during pregnancy lowers offspring IQ, and, if it does, whether it is through the smoking effect on fetal growth. METHOD: Representative samples of low birthweight (<2500 g) and normal birthweight children born in 1983-85 from inner-city and suburban communities in southeast Michigan, USA were assessed at ages 6, 11, and 17, using Wechsler intelligence tests. Smoking during pregnancy was ascertained from mothers at the first assessment; and smoking at any time was ascertained at the first and second assessment. Generalized estimating equation models were used, with children's IQ at all three assessments as outcomes (n = 798). RESULTS: Without adjustment, offspring of mothers who smoked during pregnancy scored 6.8 IQ points lower than offspring of mothers who never smoked, on average. Low birthweight children scored 5.4 IQ points lower than normal birthweight children, on average. The statistical association of maternal smoking with offspring IQ was confounded by maternal characteristics, chiefly, maternal cognitive ability as measured by IQ and education; adjustment for these factors eliminated the association. By contrast, adjustment for maternal IQ and education as well as smoking during pregnancy had a negligible effect on the low birthweight-related IQ deficit. Low birthweight did not mediate the association of smoking and lowered IQ in offspring. CONCLUSION: Maternal smoking during pregnancy is a proxy for a matrix of vulnerabilities for adverse child cognitive development and has no direct causal effect on child's IQ. The relationship of low birthweight and IQ is independent of maternal smoking and maternal cognitive abilities.     

The relationship of drinking and birth outcome in a US national sample of expectant mothers

Alcohol consumption by pregnant women and birth outcome were studied in 9953 livebirths, 3309 fetal deaths and 5332 infant deaths from the 1988 National Maternal and Infant Health Survey. In crude analyses, race, age, mother's education, prenatal care, parity, low birthweight, gestational age, smoking and alcohol consumption during pregnancy were significantly related to the occurrence of fetal deaths and infant deaths. Among women having livebirths, race, age, mother's education, prenatal care, prematurity, gestational age, smoking and alcohol consumption during pregnancy were significantly related to having a low birthweight baby (< 2500 g). In this group, women who drank more during pregnancy also smoked more, were younger and less educated than women who drank at lower levels or not at all. The relationship of alcohol consumption during pregnancy and infant birthweight for those women having livebirths was studied using multivariable linear regression. The results indicated that race, mother's education, baby's sex, parity, mother's height, mother's body mass index and smoking, but not alcohol consumption, were significantly related to birthweight. Multivariable logistic regressions were performed for the occurrence of low birthweight, fetal death and infant death. The effect of alcohol was significant in all these analyses. These results indicate that alcohol has an important relationship with birth outcome, but that for the drinking reported in this study, the alcohol effect on mean birthweight is small relative to that of other risk factors, accounting for the non-significant result in the multiple linear regression.     

Factors Associated With Quitting Smoking During Pregnancy Among Women Veterans

IntroductionLittle is known about the rates of smoking among pregnant veterans. Our objective was to examine rates of smoking during pregnancy and factors associated with quitting smoking during pregnancy.MethodsWe used data from a cohort study of pregnant veterans from 15 Veterans Health Administration facilities nationwide. Veterans who reported smoking during pregnancy were included in this analysis. Poisson regression models were used to estimate the relative risk (RR) of quitting smoking during pregnancy.ResultsOverall, 133 veterans reported smoking during pregnancy. Among this group of women who smoked, the average age was 31.6 years, 20% were Black, and 14% were Hispanic/Latino. More than one-half of women (65%) who reported smoking at the start of pregnancy quit smoking during pregnancy. Multivariable models, adjusted for history of deployment and age, indicated that prenatal care initiation at 12 or fewer weeks compared with more than 13 weeks (relative risk [RR], 2.06; 95% confidence interval [CI], 1.18–3.58), living without household smokers compared with any household smokers (RR, 1.58; 95% CI, 1.14–2.17), and first pregnancy (RR, 1.51; 95% CI, 1.17–1.95) were significant predictors of quitting versus persistent smoking during pregnancy.ConclusionsWomen veterans who quit smoking may be different than those who continue to smoke during pregnancy. Establishing prenatal care early in pregnancy, which likely includes counseling about smoking cessation, seems to be an important factor in quitting. Those for whom it is not a first pregnancy and who live with other smokers may especially benefit from such counseling.     

Infant Birth Outcomes Among Substance Using Women: Why Quitting Smoking During Pregnancy is Just as Important as Quitting Illicit Drug Use

Poor birth outcomes are associated with illicit drug use during pregnancy. While prenatal cigarette exposure has similar effects, cessation of illicit drug use during pregnancy is often prioritized over cessation of smoking. The study goal was to examine the impact of pregnancy tobacco use, relative to use of illicit drugs, on birth outcomes. Women were recruited at entry to prenatal care, with background and substance use information collected during pregnancy. Urine drug screens were performed during pregnancy, and the final sample (n = 265) was restricted to infants who also had biologic drug testing at delivery. Participants were classified by pregnancy drug use: no drugs/no cigarettes, no drugs/cigarette use, illicit drugs/no cigarettes, and illicit drugs/cigarette use. Groups differed significantly on infant birthweight, but not gestational age at delivery after control for confounders including background and medical factors. Among women who smoked, the adjusted mean birthweight gain was 163 g for those not using hard illicit drugs, while marijuana use had no effect on birth weight beyond the effect of smoking cigarettes. Women who used hard illicit drugs and did not smoke had an adjusted mean birthweight gain of 317 g over smokers. Finally, women who refrained from hard illicit drugs and smoking had a birthweight gain of 352 g. Among substance using pregnant women, smoking cessation may have a greater impact on birthweight than eliminating illicit drug use. Intervention efforts should stress that smoking cessation is at least as important to improving pregnancy outcomes as abstaining from illicit drug use.     

The sociodemographic predictors of smoking cessation among pregnant women in Canada

This study examined the sociodemographic predictors of smoking cessation attempts among pregnant women, and compared the characteristics of women who successfully quit smoking during pregnancy with those who relapsed before their child was born. Data, which were derived from the National Longitudinal Survey of Children and Youth, indicate that 23.7% of Canadian mothers smoked at some point during their pregnancies, of whom only 15.8% attempted to quit. Maternal and paternal education were the strongest predictors of successful cessation, whereas women pregnant with their first child, those who drank during pregnancy, and those who immigrated to Canada were the most likely to relapse. This study represents an important first step in identifying Canadian women at highest risk of sustained smoking during pregnancy, and is useful for the design of effective interventions, tailored to meet their needs.     

A Prospective Study of Prevalence and Predictors of Concurrent Alcohol and Tobacco Use During Pregnancy

Concurrent drinking and smoking during pregnancy is a major public health concern. Changes in these behaviours are under-researched, although essential if effective interventions are to be implemented. Hence this paper investigated characteristics of women who decreased concurrent drinking and smoking during pregnancy. 1,591 women were identified as pregnant at one of three surveys from 2000 to 2006 of the Australian Longitudinal Study on Women's Health and not pregnant at the previous survey. Relative risks (RRs) were calculated for concurrent drinkers and smokers before pregnancy of (1) decreasing drinking, (2) decreasing smoking and (3) decreasing drinking and smoking during pregnancy. Three hundred and fifty-four women (22%) were concurrent drinkers and smokers before pregnancy; of these women, 73% decreased drinking, 72% decreased smoking and 53% decreased drinking and smoking during pregnancy. Decreased concurrent drinking and smoking was significantly higher among women who had at least 12 years education (RRs: 1.5–1.6), who drank at least 1–2 days/week (RRs: 1.5–1.6) and who had 3 or more drinks per occasion (RRs: 1.6–1.8), and significantly lower among heavy smokers, mothers of other children (RRs: 0.8) and disadvantaged women: those stressed about money, with poor mental health, low social support and experience of partner violence (RRs: 0.6–0.7). Clearly programs are needed to tackle concurrent drinking and smoking during pregnancy. Given many pregnancies are unplanned, these programs should target drinking and smoking before and during pregnancy, as well as disadvantaged women, to reduce the deleterious effects of concurrent substance use on their babies and themselves.     

Interactions between fetal HLA-DQ alleles and maternal smoking influence birthweight

Maternal smoking during pregnancy inhibits fetal growth, and is a major cause of childhood and adult morbidity, including increased risks of cardiovascular disease and diabetes. However, the use of birthweight as a proxy for future smoking-related morbidity is hindered by its wide variability, suggesting a role for other birthweight-modifying factors. We report here, for the first time, that interactions between specific fetal HLA-DQA1 and DQB1 alleles and maternal smoking can influence birthweight. We compared mean birthweights of a series of term, HLA-DQ typed white UK newborns (n = 552) whose mothers had either smoked (n = 211) or not smoked (n = 341) during pregnancy. Maternal smoking during pregnancy resulted in an average birthweight reduction of 244 g, but the combined effects of maternal smoking and fetal DQA1*0101 or DQB1*0501 alleles resulted in a 230 and 240 g further reduction in mean birthweight, respectively, resulting from interactions between smoking and these DQ types. Other fetal DQ allele-specific interactions with maternal smoking are suggested by a "protective" effect on smoking-associated birthweight reduction in newborns typing for DQA1*0201 and DQB1*0201. Our results suggest biological interactions between maternal cigarette smoking during pregnancy and specific fetal DQ alleles that affect fetal growth. The precise nature of these interactions merits further investigation, as knowledge of fetal HLA-DQ type may be useful in refining risk estimates of severe fetal growth restriction because of maternal smoking during pregnancy.     

The influence of maternal cigarette smoking, snuff use and passive smoking on pregnancy outcomes: the Birth To Ten Study

This article describes the patterns and effects of maternal snuff use, cigarette smoking and exposure to environmental tobacco smoke during pregnancy on birthweight and gestational age, in women living in Johannesburg and Soweto in 1990. A cohort of 1593 women with singleton live births provided information about their own and household members' usage of tobacco products during pregnancy. The women completed a questionnaire while attending antenatal services. Data on gestational age and birthweight were obtained from birth records. Women who smoked cigarettes or used snuff during pregnancy accounted for 6.1% and 7.5% of the study population respectively. The mean birthweight of non-tobacco users was 3148 g [95% CI 3123, 3173] and that of the smokers 2982 g [95% CI 2875, 3090], resulting in a significantly lower mean birthweight of 165 g for babies of smoking mothers (P = 0.005). In contrast, women using snuff gave birth to infants with a mean birthweight of 3118 g [95% CI 3043, 3192], which is a non-significant (P = 0.52) decrease (29.4 g) in their infants' birthweights compared with those not using tobacco. A linear regression analysis identified short gestational age, female infant, a mother without hypertension during pregnancy, coloured (mixed racial ancestry), and Asian infants compared with black infants, lower parity, less than 12 years of education and smoking cigarettes as significant predictors of low birthweight, while the use of snuff during pregnancy was not associated with low birthweight. The snuff users, however, had a significant shorter gestational age than the other two groups of women. The birthweight reduction adjusted for possible confounders was 137 g [95% CI 26.6, 247.3 (P = 0.015)] for cigarette smokers and 17.1 g [95% CI -69.5, -102.7, P = 0.69] for snuff users respectively, compared with the birthweight of non-tobacco users. Among women who did not smoke cigarettes or use snuff, exposure to environmental tobacco smoke did not result in significant effects on the birthweight of their infants. In conclusion, infants of cigarette smokers had significantly lower birthweights than those of non-tobacco users or snuff users who are exposed to nicotine during pregnancy. Passive smoking did not affect birthweight significantly in this population.     

The effects of maternal smoking on fetal and infant mortality

Although maternal cigarette smoking has been shown to reduce the birth weight of an infant, previous findings on the relation between smoking and fetal and infant mortality have been inconsistent. This study used the largest data base ever available (360,000 birth, 2,500 fetal death, and 3,800 infant death certificates for Missouri residents during 1979-1983) to assess the impact of smoking on fetal and infant mortality. Multiple logistic regression was used to estimate the joint effects of maternal smoking, age, parity, education, marital status, and race on total mortality (infant plus fetal deaths). Compared with nonsmoking women having their first birth, women who smoked less than one pack of cigarettes per day had a 25% greater risk of mortality, and those who smoked one or more packs per day had a 56% greater risk. Among women having their second or higher birth, smokers experienced 30% greater mortality than nonsmokers, but there was no difference by amount smoked. The prevalence of smoking in this population was 30%. It was estimated that if all pregnant women stopped smoking, the number of fetal and infant deaths would be reduced by approximately 10%. The higher rate of mortality among blacks compared with whites could not be attributed to differences in smoking or the other four maternal characteristics studied. In fact, the black-white difference was greater among low-risk women (e.g., married multiparas aged 20 and over with high education) than among high-risk women (e.g., unmarried teenagers with low education).     

Does gravidity influence smoking behaviour in pregnancy? A comparison of multigravid and primigravid women

This study used the data from a retrospective cross-sectional survey to describe the prevalence of smoking in pregnancy in a large UK sample, over more than 20 years of pregnancies. The main objective was to determine whether women in their second or subsequent pregnancy are more or less likely than primigravidae to change their smoking behaviour. The participants were 7506 ever-pregnant women, from 7702 who answered the second stage of a survey of reproductive history in 2001-02, sent to 10 828 women, aged 18-55 years on the UK electoral register. These women gave detailed information on their last pregnancy. The main outcome measure was self-reported cigarette consumption in the first trimester of pregnancy. Nineteen per cent (1417/7506) of women in this sample smoked in the first trimester of the reported pregnancy. The data showed that there had been a decrease over the last 20 years in smoking prevalence, but this trend was not statistically significant after adjustment for confounding (P(trend) = 0.07). There was evidence that multigravidae were more likely to smoke in their pregnancies than were primigravidae (adjusted OR = 1.24, [95% CI 1.01, 1.53]), with a highly significant trend with increasing pregnancy order (P(trend) < 0.0001). Over time, women who reported smoking before pregnancy (n = 1926), showed a decreasing trend in continuing to smoke the same amount after recognising their pregnancies (P(trend) < 0.0001). After adjustment, multigravid smokers were almost 75% more likely than primigravid smokers to continue to smoke with no change in consumption (adjusted OR = 1.74, [95% CI 1.32, 2.28]), with a clear trend found with increasing pregnancy order (P(trend) = 0.001). In this UK population-based study, multigravidae were more likely to smoke in pregnancy than women pregnant for the first time. If already a smoker, they were much less likely to cut down their smoking once they found out they were pregnant, regardless of age. This suggests that a great deal of the burden of morbidity associated with smoking in pregnancy is in the multigravid group.     

A population-based cohort study of the relation between maternal birthweight and risk of gestational diabetes mellitus in four racial/ethnic groups

Intrauterine growth retardation and low birthweight have been associated with an increased risk of insulin resistance and type II diabetes later in life. We hypothesised that maternal low birthweight is associated with an increased risk of gestational diabetes mellitus (GDM). Study subjects comprised women giving birth in Washington State between 1987 and 1995. Information for 21,528 births to non-Hispanic white women, 6359 to African-American women, 7456 to Native American women and 6496 to Hispanic women was available for analysis. All information was derived from statewide computerised vital records and hospital discharge summaries of obstetric and neonatal admissions with linkage to birth certificates of mothers. Maternal birthweight was collected from subjects' birth certificates. Information from both the birth certificates and the obstetric and neonatal admissions database was used to determine whether subjects developed GDM. Poisson regression models were estimated to calculate unadjusted and adjusted risk ratios (RRs) and 95% confidence intervals (CIs) for GDM by categories of maternal birthweight. The cumulative incidence of GDM among non-Hispanic white, African-American, Native American and Hispanic women was 2.8, 2.6, 2.7 and 3.0% respectively. After adjusting for maternal age, parity, cigarette smoking, history of chronic hypertension and participation in the Medicaid programme, non-Hispanic white women with a birthweight < 2000 g were 1.7 times more likely to have had their pregnancy complicated by GDM (RR = 1.7; 95% CI 0.8, 3.3) than those with a birthweight 3000-3999 g. The corresponding adjusted RRs for African-American, Native American, and Hispanic women were 2.8 [95% CI 1.2, 6.1], 3.1 [95% CI 1.2, 8.2] and 2.4 [95% CI 0.9, 6.0] respectively. Among African-American women, those with a birthweight > or = 4000 g also experienced a twofold increased risk of GDM (RR = 2.1; 95% CI 1.0, 4.1). This association of high birthweight and increased GDM risk was not found among women in the other three racial/ethnic groups. These findings suggest that individuals with low birthweight constitute a group at increased risk for GDM.     

Does maternal smoking during pregnancy cause childhood overweight?

The objective of this study was to examine a possible association between maternal smoking in pregnancy and childhood overweight. From a population-based cohort of 5722 women from Trondheim, Bergen (Norway) and Uppsala (Sweden) enrolled in early pregnancy during 1986-92, a random sample of 482 women was selected for participation. They were followed up throughout pregnancy, and their children from birth until 5 years of age. Data on maternal smoking and diet, socio-economic determinants and breast feeding were recorded prospectively. During pregnancy and childhood, anthropometric measures were also recorded. Maternal smoking status was based on reported number of cigarettes smoked in week 17 of pregnancy. Child overweight was defined by body mass index (BMI) and sum of skinfold thickness (SFT) >or= 85th percentile at 5 years of age. Children of mothers who smoked in pregnancy had increased risk of overweight at 5 years of age (RR 2.5, 95% CI 1.5, 4.2 for BMI; and RR 1.8, 95% CI 1.1, 3.0 for SFT). Adjusting for maternal diet, breast feeding, maternal obesity and socio-economic status did not suggest confounding. However, adjustment for birthweight increased the observed risk. A linear increase in BMI and SFT was observed with increasing number of cigarettes smoked. In conclusion, smoking during pregnancy may be a risk factor for development of childhood overweight. This study may support the hypothesis of 'fetal origin of adult disease', but the risk of overweight associated with smoking during pregnancy was independent of intrauterine growth retardation, and may thus be attributed to specific effects of cigarette smoke.     

Maternal smoking and the risk of polyhydramnios.

BACKGROUND. Washington State birth certificates were used to conduct a population-based case-control study to assess the possible association of maternal smoking with polyhydramnios. METHODS. All singleton births complicated by polyhydramnios (n = 557) were identified from the vital records for the years 1984 to 1987. For comparison, 1671 records were randomly selected for the same years from singleton births uncomplicated by polyhydramnios. RESULTS. Women who reportedly smoked prenatally were found to be at increased risk for polyhydramnios (relative risk [RR] = 1.7, 95% confidence interval [CI] = 1.5-2.1, adjusted for marital status, maternal age, and parity). When women with conditions known to be associated with polyhydramnios were excluded, the risk for those who smoked prenatally remained elevated (RR = 1.8, 95% CI = 1.1-2.3). CONCLUSION. Overdistention of the uterus from polyhydramnios may cause a variety of pregnancy complications. The observed association of smoking with polyhydramnios may be a further indication for public health interventions aimed at preventing smoking during pregnancy.