The effect of smoking cessation during pregnancy on preterm delivery and low birthweight

BACKGROUND: Evidence exists that maternal cigarette smoking is associated with preterm birth. Our purpose was to investigate the relation between maternal smoking cessation at different points during pregnancy and the preterm delivery rate and low birthweight. METHODS: Data from the 1988 National Health Interview Survey were analyzed. The study included women who gave birth to children within 6 years of the 1988 interview date (N = 4876). Preterm delivery and infant low birthweight were the main outcome measures. These measures were compared with maternal smoking status during pregnancy. Logistic regression models were computed to control for maternal age at the time of birth, parity, race, and total family income. RESULTS: Women who did not smoke cigarettes during pregnancy were less likely to give birth prematurely (5.9% vs 8.2%, P = .003) or give birth to a low-birthweight baby (5.5% vs 8.9%, P < .001) than women who smoked at some time during the year before giving birth. A significant association existed between maternal smoking status and both preterm delivery and low birthweight. Compared with those who smoked beyond the first trimester, those who quit smoking within the first trimester had reductions in the proportion of preterm deliveries (6.7% vs 9.1%) and low birthweight infants (7.9% vs 9.6%). CONCLUSIONS: Low birthweight and preterm delivery are reduced in women who stop smoking in the first trimester of pregnancy.