[Effects of tobacco habit, second-hand smoking and smoking cessation during pregnancy on newborn's health].

Background And Objective: Tobacco during pregnancy affects the health of the newborn. The aim was to assess the effect of maternal exposure to active and passive tobacco and of smoking cessation on the risk of preterm deliveries and birth weight, taking into account other risk factors.

Patients And Method: Longitudinal study conducted in 282 healthy pregnant women. General, obstetrical and hematological data were collected as it was the smoking habit during pregnancy. Pregnant women were classified as "exposed to smoke" (active smoker and passive smoker) and "unexposed to smoke" (non-smokers and women who quitted smoking during pregnancy).

Results: A percentage of 59.2 were non-smokers, 18.4% active smokers, 8.5% second-hand smokers and 13.8% had stopped smoking. Unexposed pregnant women who stopped smoking had the same risk of premature deliveries and children with similar birth weight as non-smoker women. Active and second-hand smokers were at higher risk of preterm deliveries than non-smokers (odds ratio [OR] 6.5, 95% confidence interval [95% CI] 1.4-30.8 and OR 6.2, 95% CI 1.0-38.9, respectively); however, higher levels of hemoglobin in the 1st and 3rd trimester exerted a protective effect (OR 0.9, 95% CI 0.8-0.9). Active and second-hand smokers had babies weighing less than non-smokers (around 129 and 178g less, respectively).

Conclusions: Active or passive exposure to smoke during pregnancy and lower hemoglobin levels are associated with an increased risk of premature deliveries and lower birth weight. Stopping smoking during pregnancy prevents these detrimental effects.