Maternal cigarette smoking during pregnancy in relation to oral clefts

Studies on maternal smoking in relation to oral cleft defects have yielded inconsistent findings, with results ranging from no association to sixfold increases in risk. The authors examined this relation in a case-control study conducted in Boston, Massachusetts, Philadelphia, Pennsylvania, Toronto, Ontario, Canada, and the state of Iowa during the years 1983-1987, in which mothers of malformed infants were interviewed within 6 months after delivery about prenatal events and exposures. Maternal cigarette smoking during pregnancy for 400 infants with cleft lip with or without cleft palate and for 215 infants with cleft palate alone was compared with that for 2,710 infants with other malformations (controls). Relative risks (and 95% confidence intervals) were estimated for smokers of 1-14, 15-24, and greater than or equal to 25 cigarettes per day relative to never smokers; the respective estimates for cleft lip with or without cleft palate were 1.2 (95% confidence interval (CI) 0.9-1.6), 1.4 (95% CI 1.0-2.1), and 0.7 (95% CI 0.3-1.6), and for cleft palate alone, estimates were 1.0 (95% CI 0.7-1.5), 0.9 (95% CI 0.5-1.5), and 0.8 (95% CI 0.3-2.2). Relative risks were also close to unity for case subgroups divided according to the presence or absence of an associated malformation. Multivariate control of several potential confounders did not alter these estimates. Based on this large series of cases, maternal smoking during pregnancy does not appear to increase the risk of oral clefts.     

Maternal cigarette smoking and oral clefts: a population-based study.

Analyses of 1984 data from the Maryland Birth Defects Reporting and Information System indicate that mothers of infants with oral clefts (cleft lip with or without cleft palate; and cleft palate) smoked more during pregnancy than mothers of infants with other defects (odds ratio OR of 2.56 and 2.39, respectively). There was a dose-response relation between the daily amount smoked and the risk of clefting. Adjustment for available confounding variables did not account for the association between smoking and oral clefts.     

Maternal cigarette smoking and the risk of tubal pregnancy.

The association between maternal smoking and the occurrence of tubal pregnancy was evaluated in a population-based case-control study of members of the Group Health Cooperative of Puget Sound, Seattle, Washington. Women hospitalized with tubal pregnancy from October 1981 through September 1986 (n = 274) were compared with reproductive-age women who were at risk of becoming pregnant during the same time period (n = 727). The relative risk of tubal pregnancy associated with ever having smoked cigarettes was 1.3 (95% confidence interval (CI) 1.0-1.8). Compared with women who had never smoked, those who smoked at the time of conception had a 40% increase in the risk of tubal pregnancy (95% CI 1.0-2.0). These results support earlier epidemiologic and nonepidemiologic reports of a greater risk of tubal pregnancy associated with current or recent maternal cigarette smoking.     

Chemical exposure during pregnancy and oral clefts in newborns

This article presents a literature review on the risk factors for oral clefts (lip and/or palate), emphasizing discussion of maternal exposure to endocrine disruptors. Several studies have identified the risk of cigarette smoking and alcohol consumption, use of anticonvulsant drugs, and exposure to organic solvents. A protective effect has been shown for supplementation with folic acid. As with other chemicals, the risk associated with exposure to sex hormones is still obscure, although some authors describe a moderate risk level. New studies addressing this hypothesis need to be conducted, while the population exposed to these endocrine disrupters is increasing.     

Maternal cigarette smoking and pregnancy outcome

Maternal smoking rates in pregnancy have declined, particularly in the non-manual social classes, and perinatal mortality rates have fallen over the last 20 years. We have therefore re-evaluated the relationship between maternal cigarette smoking and pregnancy outcome against this background. A total of 608 stillbirths and 634 infant deaths were identified using the All Wales Perinatal Survey. The cause of death was classified using the clinicopathological system. Maternal smoking rates and social class groupings were compared with those in a cohort of 16047 survivors born to women resident in South Glamorgan. The smoking rate was 37.8% in mothers of babies who died compared with 27.2% in mothers of survivors, an odds ratio (OR) of 1.63 [95% CI 1.44, 1.84]. The OR for unexplained stillbirth was 1.72 [95% CI 1.38, 2.13], placental abruption 2.07 [95% CI 1.29, 3.31], infection 3.70 [95% CI 2.23, 6.13] and sudden infant death syndrome 4.84 [95% CI 3.05, 7.69]. Maternal smoking was not associated with death due to prematurity or a congenital anomaly. Despite changes in smoking habits and the causes of perinatal death, smoking during pregnancy continues to be strongly associated with fetal and infant mortality. It is important that health promotion activities are effective in reducing smoking during pregnancy.     

Maternal smoking during pregnancy and smoking by adolescent daughters.

OBJECTIVES. Since cigarette smoking in adolescence represents a crucial entry point in the progression to illicit drugs, risk factors for adolescent smoking have public health implications. The influence of mothers on children's smoking appears to be greater than that of fathers. To explain the selective influence of mothers, we examined the consequences of maternal smoking during pregnancy in two longitudinal samples. METHODS. Analyses were conducted on follow-up interview data from two dyadic samples of mothers and firstborn adolescents for whom data on maternal smoking during and after pregnancy were available (192 mother-child pairs originating from New York State and 797 dyads from a national sample). RESULTS. In both samples, maternal smoking during pregnancy, when postnatal smoking was controlled, selectively increased the probability that female children would smoke and would persist in smoking (adjusted odds ratios of about 4). CONCLUSIONS. The findings suggest that nicotine or other substances released by maternal smoking can affect the fetus, perhaps through the nicotinic input to the dopaminergic motivational system, so as to predispose the brain in a critical period of its development to the subsequent addictive influence of nicotine consumed more than a decade later in life.     

Maternal smoking during pregnancy and the risk of congenital urinary tract anomalies.

To study maternal smoking during pregnancy and the risk of congenital urinary tract anomalies, we interviewed mothers of 118 affected infants born to residents of western Washington State during 1990 and 1991 and mothers of 369 control infants randomly selected from those without birth defects delivered during those years in five hospitals in King County, Washington. Maternal smoking was associated with an increased risk of congenital urinary tract anomalies in offspring (adjusted odds ratio [OR] = 2.3; 95% confidence interval [CI] = 1.2, 4.5). This risk was higher among light smokers (1-1000 cigarettes during the pregnancy) (OR = 3.7; 95% CI = 1.7, 8.6) than among heavy smokers (OR = 1.4; 95% CI = 0.6, 3.3). Our results corroborate previous findings and support the hypothesis of a causal relation.     

Increased risk of ectopic pregnancy with maternal cigarette smoking.

As part of a case-control study of ectopic pregnancy, we evaluated the potential etiologic role of cigarette smoking. Maternal cigarette smoking at the time of conception was associated with an increased risk of ectopic pregnancy with a dose-response relationship (adjusted odds ratios: 1.30 to 2.49). On the other hand, partner's smoking was not associated with ectopic pregnancy. The study provides a supplementary argument towards a causal effect of smoking in the development of ectopic pregnancy.     

Maternal smoking during pregnancy and childhood obesity

A recent cohort study suggested that maternal smoking during pregnancy might be a risk factor for childhood obesity. Data from the obligatory school entry health examination in six Bavarian (Germany) public health offices in 1999-2000 were used to assess the relation between maternal smoking during pregnancy and childhood obesity (n = 6,483 German children aged 5.00-6.99 years). A body mass index greater than the 90th percentile was defined as overweight, and a body mass index greater than the 97th percentile was defined as obesity. The main exposure was maternal smoking during pregnancy. The prevalences of overweight and obesity, expressed as percentages, increased in the following order: never smoked (overweight: 8.1, 95% confidence interval (CI): 7.2, 9.0; obesity: 2.2, 95% CI: 1.7, 2.7); less than 10 cigarettes daily (overweight: 14.1, 95% CI: 11.1, 17.7; obesity: 5.7, 95% CI: 3.7, 8.2); and 10 or more cigarettes daily (overweight: 17.0, 95% CI: 10.1, 26.2; obesity: 8.5, 95% CI: 3.7, 16.1). The adjusted odds ratios for maternal smoking during pregnancy were 1.43 (95% CI: 1.07, 1.90) for overweight and 2.06 (95% CI: 1.31, 3.23) for obesity. A dose-dependent association between overweight/obesity and maternal smoking during pregnancy was observed that could not be explained by a wide range of confounders, suggesting that intrauterine exposure to inhaled smoke products rather than lifestyle factors associated with maternal smoking accounts for this finding.     

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.     

Maternal smoking during pregnancy and anthropometric measurements of newborns: a population-based study in southern of Brazil

This cross-sectional study aimed to investigate the prevalence of maternal smoking during pregnancy and its impact on anthropometric measurements of newborns. A standardized questionnaire was applied to all pregnant women admitted for delivery in the maternity units in Rio Grande, Rio Grande do Sul State, Brazil, in 2007. Measurements were taken of the newborns' weight, length, and head circumference. Prevalence rates were 23% for maternal smoking during pregnancy and 29% for exposure to environmental tobacco smoke. After adjusting for potential confounding factors, compared with those whose mothers never smoked, newborns whose mothers smoked throughout pregnancy showed average decreases of 223.4 g in birth weight (95%CI: 156.7;290.0), 0.94 cm in birth length (95%CI: 0.60;1.28), and 0.69 cm in head circumference (95%CI: 0.42-0.95). In conclusion, prevalence of maternal smoking during pregnancy was high in this municipality. Maternal smoking during pregnancy was inversely associated with birth weight, length, and head circumference.     

Maternal cigarette smoking and the risk of pregnancy-induced hypertension and eclampsia

BACKGROUND: Although previous studies have found that maternal smoking decreases the risk of pregnancy-induced hypertension (PIH), the difference of this effect between primiparous and multiparous women has not been well studied and the results of the exposure-response relationships between maternal smoking and PIH are inconsistent. No previous study has specifically examined the relationship between maternal smoking and eclampsia. METHODS: We analysed data from a population-based retrospective cohort study of 3 153 944 singleton pregnancies in the US. The data were derived from the national linked birth/infant mortality database for 1998. Multiple logistic regressions were used to describe the relationship between cigarette smoking and PIH and eclampsia. RESULTS: The adjusted odds ratios (ORs) [95% confidence intervals (95% CIs)] for PIH were 0.80 (0.77-0.83) for primiparous women and 0.81 (0.78-0.83) for multiparous women among smokers compared with non-smokers. The corresponding adjusted ORs (95% CIs) for eclampsia were 0.74 (0.66-0.82) and 0.75 (0.68-0.83), respectively. For PIH, the adjusted OR (95% CI) for smokers vs non-smokers were 0.82 (0.79-0.86), 0.81 (0.78-0.83), 0.80 (0.77-0.83), and 0.88 (0.79-0.98), respectively, for 1-5, 6-10, 11-20, and >20 cigarettes per day (test for trend: P = 0.86). The corresponding figures for eclampsia were 0.85 (0.75-0.95), 0.74 (0.66-0.82), 0.68 (0.58-0.78), and 0.73 (0.49-1.04), respectively (test for trend: P = 0.02). CONCLUSION: Maternal cigarette smoking decreases the risk of PIH and eclampsia, with a significant inverse exposure-response relationship apparent for eclampsia.     

Maternal smoking and environmental tobacco smoke exposure and the risk of orofacial clefts

BACKGROUND: Smoking during pregnancy has been associated with orofacial clefts in numerous studies. However, most previous studies have not been able to assess the relation between maternal smoking and specific phenotypes (eg, bilateral clefts). METHODS: We examined the association between periconceptional maternal smoking, environmental tobacco smoke (ETS) exposure, and cleft lip with or without cleft palate (CLP) (n = 933) and cleft palate only (CPO) (n = 528) compared with infants with no major birth defects (n = 3390). Infants were born between 1 October 1997 and 31 December 2001, and exposures were ascertained from maternal telephone interviews for the National Birth Defects Prevention Study. We excluded infants who had a first-degree relative with an orofacial cleft. Effect estimates were adjusted for folic acid use, study site, prepregnancy obesity, alcohol use, gravidity, and maternal age, education, and race/ethnicity. RESULTS: Periconceptional smoking was associated with CLP (odds ratio = 1.3; 95% confidence interval = 1.0-1.6), and more strongly associated with bilateral CLP (1.7; 1.2-2.6), with a weaker association observed for CPO. Heavy maternal smoking (25+ cigarettes/day) was associated with CLP (1.8; 1.0-3.2), bilateral CLP (4.2; 1.7-10.3), and CPO with Pierre Robin sequence (2.5; 0.9-7.0). ETS exposure was not associated with CLP or CPO. CONCLUSIONS: This study confirmed the modest association between smoking and orofacial clefts that has been consistently reported, and identified specific phenotypes most strongly affected.     

Maternal smoking during pregnancy and limb reduction malformations in Sweden.

OBJECTIVE: This study was undertaken to investigate a possible connection between different types of limb reduction defects and maternal smoking during pregnancy. METHODS: With the use of the Swedish health registries, 610 cases of limb reduction malformations were selected from among 1 109 299 infants born between 1983 and 1993 with known smoking exposure in early pregnancy. Confounders such as maternal age and parity were controlled for with the use of the Mantel-Haenszel technique. RESULTS: The odds ratio for any maternal smoking among all cases of limb reductions was 1.26 (95% confidence interval = 1.06, 1.50). The main subgroups of limb reduction defects showed similar odds ratios, but in longitudinal reduction defect, only unilateral cases showed an association with maternal smoking. CONCLUSIONS: This study supports an association between maternal smoking and limb reduction malformations, but further work is needed before a causal inference can be made.     

Interaction between smoking and body mass index and risk of oral clefts

PurposeTo examine maternal smoking and body mass index (BMI) interactions in contributing to risk of oral clefts.MethodsWe studied 4935 cases and 10,557 controls from six population-based studies and estimated a pooled logistic regression of individual-level data, controlling for study fixed effects and individual-level risk factors.ResultsWe found a significant negative smoking–BMI interaction, with cleft risk with smoking generally declining with higher BMI. For all clefts combined, the odds ratio for smoking was 1.61 (95% confidence interval [CI]: 1.39–1.86) at BMI 17 (underweight), 1.47 (95% CI: 1.34–1.62) at BMI 22 (normal weight), 1.35 (95% CI: 1.22–1.48) at BMI 27 (overweight), 1.21 (95% CI: 1.04–1.41) at BMI 33 (obese), and 1.13 (95% CI: 0.92–1.38) at BMI 37 (very obese). A negative interaction was also observed for isolated clefts and across cleft types but was more pronounced for cleft lip only and cleft palate only.ConclusionsOur findings suggest that the risk of oral clefts associated with maternal smoking is largest among underweight mothers, although the smoking–BMI interaction is strongest for cleft lip only and cleft palate only. BMI was not protective for the effects of smoking; a clinically relevant increase in smoking-related cleft risk was still present among heavier women.