Higher risk of stillbirth among lower and middle income women who do not use tobacco, but live with smokers

Objective. To investigate pregnancy outcomes among women living with smokers. Design. Data were from a cohort study of 1,217 women recruited during 3-7th month of pregnancy and 96% followed-up after delivery. The main objective was to investigate effects of smokeless tobacco on pregnancy outcomes. Setting. Lower and middle-class neighborhoods in Mumbai, India. Community health volunteers who had good rapport with the local population collaborated with the study personnel to help locate and interact with potential participants. Population. Singleton births from non-tobacco users; n = 924/903/802 for stillbirth/gestational age/birthweight analysis. Non-smoking women who lived with smokers (28%) were categorized as 'exposed' to second hand smoke (SHS). Methods. House-to-house surveys with questionnaire administration and medical records abstraction by trained personnel at recruitment and follow-up. Outcome measures. Stillbirth (no evidence of life at birth after at least 20 weeks of gestation), low birthweight (<= 2,499 g) and preterm birth (<= 258 days of gestation). Results. Rates of low birthweight and preterm birth were not significantly different between exposed and non-exposed. Hazard ratio for stillbirth in SHS exposed women (n = 261) was 2.2 (95% confidence interval 1.1-4.4). Survival times differed significantly between exposed and non-exposed, p = 0.012. Exposed and non-exposed groups differed significantly by education, socioeconomic status, parity and access of antenatal care. After adjustment for these potential confounders in Cox proportional hazards models ( gestational age in days as timescale), hazard ratios for stillbirth in the exposed group remained unchanged: 2.1 (1.1-4.3). Conclusions. Pregnant women living with smokers in their household have a significantly higher risk of stillbirth, independent of differences in socio-demographic characteristics and antenatal care.