Fetal growth restriction, low birth weight, and preterm birth: Effects of active or passive smoking evaluated by maternal expired CO at delivery, impacts of cessation at different trimesters

INTRODUCTIONThe objectives of this study were to evaluate the effect of cessation of active smoking during the 1st, 2nd, and 3rd trimesters of pregnancy on the risk of reduced birth weight and prematurity using an exhaled carbon monoxide biomarker with a cut-off value ≥3 ppm as well as the effects of passive smoking. METHODSThis was a multicenter prospective cohort study involving pregnant smokers and non-smokers. Pregnant smokers were identified at the first prenatal visit before 15 weeks of amenorrhea by the number of cigarettes smoked per day and by the carbon monoxide breath test. Women were classified into 6 groups: non-smokers, passive smokers, first trimester cessation, second trimester cessation, third trimester cessation, and smoking throughout pregnancy. Smoking cessation was defined if the pregnant woman reported quitting smoking and if she achieved an exhaled CO level of