RESUMO
OBJECTIVE: Smoking cessation is associated with weight gain. We first examined the associations of smoking cessation in early-pregnancy with gestational weight gain and subsequently evaluated the risks of pregnancy complications among women who quit smoking in early-pregnancy according to their gestational weight gain. METHODS: In a population-based prospective cohort study among 7,389 women, we measured weight in each pregnancy period. Information on smoking and pregnancy complications was obtained from questionnaires and medical records. RESULTS: As compared to continued smoking during pregnancy, smoking cessation in early-pregnancy was not associated with gestational weight gain. Smoking cessation in early-pregnancy was associated with decreased risks of delivering small-for-gestational-age infants (Odds Ratio (OR) 0.52 (95 % Confidence Interval (CI) 0.37, 0.75)), but with increased risks of pre-eclampsia (OR 2.07 (95 % CI 1.01, 4.27)) and delivering large-for-gestational-age infants (OR 2.11 (95 % CI 1.45, 3.09)). Among women who quit smoking in early-pregnancy with >12 kg weight gain, the risks of pre-eclampsia and delivering large-for-gestational-age infants were slightly increased. CONCLUSION: As compared to continued smoking during pregnancy, smoking cessation in early-pregnancy is not associated with increased gestational weight gain. Among women who quit smoking in early-pregnancy, higher gestational weight gain does not strongly affect their risks of pregnancy complications.