Impact of maternal anthropometry and smoking on neonatal birth weight.

The purpose of this study was to determine the effect of maternal pre-pregnancy body mass index (BMI) and maternal smoking habits on neonatal birth weight. We reviewed 10,240 normal singleton term pregnancies between 1985 and 1995 at the University Department of Obstetrics and Gynecology, Vienna. Birth weights of infants of overweight smokers were greater than those of smokers in general and similar to birth weights of nonsmokers, but smoking did have a fetal growth-retarding effect in overweight smoking mothers. Infants of underweight mothers who increased their daily cigarette consumption during pregnancy had significantly lowest birth weight. Our results suggest that the negative effects of smoking during pregnancy cannot be mitigated by a higher pre-pregnancy BMI and/or an improved weight gain during pregnancy. Especially the infants of underweight mothers benefit from their mothers' decision to cease smoking.