Effect of Smoking Cessation at Different Trimesters on Pregnancy Outcome

Abstract

Objective: To investigate the effect of smoking cessation at various trimesters on pregnancy outcome.
Methods: Pregnant smokers who were followed up at two public hospitals in Hong Kong between April 2011 and May 2015 were retrospectively reviewed. Based on their self-reported smoking status, women were categorised as having quit smoking in the (1) first trimester, (2) second trimester, or (3) third trimester, or (4) having continued to smoke throughout pregnancy. The four groups were compared in terms of maternal characteristics and pregnancy outcomes.
Results: During the study period, among 18,816 pregnant women, 314 (1.7%) still smoked. Of them, 275 were included: 147 (53.5%) continued to smoke throughout pregnancy and 74 (26.9%), 38 (13.8%), and 16 (5.8%) quit smoking in the first, second, and third trimester, respectively. The four groups were comparable in terms of maternal characteristics. Women who smoked fewer cigarettes were more likely to quit smoking at an earlier trimester (p<0.001). Women who smoked ≤5 cigarettes per day were more likely to quit smoking during pregnancy. Baby
birthweight was 7% lower in women who continued to smoke throughout pregnancy than in women who quit smoking during the first trimester (2915 g vs. 3118 g, p=0.048).
Conclusion: Baby birthweight was lower in women who continued to smoke throughout pregnancy. Healthcare professionals should actively advise women about smoking cessation to improve pregnancy outcome, particularly those who smoke ≥6 cigarettes per day.