title: Maternal smoking, body mass index, and neural tube defects.
abstract: The Swedish health registries were used to investigate a possible effect on the incidence of neural tube defects (NTDs) of maternal smoking and maternal body mass index (BMI) (kg/m2). Among 1,199,701 infants born in 1983-1993 with known smoking exposure in early pregnancy, 621 infants with NTDs were selected. After controlling for year of birth, maternal age, parity, education level, BMI, and immigrant status (yes/no), a highly significant, protective effect of maternal smoking on the incidence of NTDs was found. The adjusted odds ratios (OR) and (95% confidence intervals (CI)) for maternal smoking among infants with NTDs (total), anencephaly, and spina bifida were 0.75 (0.61-0.91), 0.49 (0.28-0.85), and 0.76 (0.61-0.95), respectively. A protective dose-response effect of smoking was indicated but was not statistically significant. The association between NTDs and maternal BMI found in earlier studies was supported. Women with BMI >26.0 were found to be at higher risk of having an infant with NTD compared with women in other BMI classes (adjusted OR=1.35, 95% CI 1.00-1.83). For women with BMI > or =29, the corresponding odds ratio was 1.29 (0.81-2.05). No obvious explanation was found, either for the detected association between NTDs and BMI, or for the protective effect of maternal smoking.
authors.affiliation: Tornblad Institute, University of Lund, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Källén
mesh_terms: D000328:Adult; D015992:Body Mass Index; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009436:Neural Tube Defects / Q000453:epidemiology* / Q000209:etiology; D009765:Obesity / Q000150:complications*; D016017:Odds Ratio; D011247:Pregnancy; D012042:Registries; D012907:Smoking / Q000009:adverse effects*; D013548:Sweden / Q000453:epidemiology