Smokeless tobacco use, birth weight, and gestational age: population based, prospective cohort study of 1217 women in Mumbai, India.

OBJECTIVE To study the effect of using smokeless tobacco during pregnancy on babies' birth weight and gestational age at birth. DESIGN Population based, prospective cohort study using a house to house approach. SETTING Eight primary health post areas in the city of Mumbai (Bombay), India. PARTICIPANTS 1217 women who were three to seven months pregnant and planning to deliver in the study area. 1167 women (96%) were followed up. MAIN OUTCOME MEASURES Birth weight and gestational age in singleton births. RESULTS Smokeless tobacco use was associated with an average reduction of 105 g in birth weight (95% confidence interval 30 g to 181 g) and a reduction in gestational age of 6.2 (3.0 to 9.4) days. The odds ratio for low birth weight was 1.6 (1.1 to 2.4), adjusted by logistic regression for maternal age, education, socioeconomic status, weight, anaemia, antenatal care, and gestational age. The adjusted odds ratio for preterm delivery (< 37 weeks) was 1.4 (1.0 to 2.1); for delivery before 32 weeks it was 4.9 (2.1 to 11.8) and before 28 weeks it was 8.0 (2.6 to 27.2). CONCLUSIONS Consumption of smokeless tobacco during pregnancy decreases gestational age at birth and birth weight independent of gestational age. It should receive specific attention as a part of routine prenatal care.