Head circumference at birth and exposure to tobacco, alcohol and illegal drugs during early pregnancy.

AIMS: We aimed to assess the effects of exposure to tobacco smoke, alcohol and illegal drugs during early pregnancy on the head circumference (HC) at birth of otherwise healthy neonates.
METHODS: A follow-up study from the first trimester of pregnancy to birth was carried out in 419 neonates. An environmental reproductive health form was used to record data of substance exposure obtained during the first obstetric visit at the end of the first trimester. A multiple linear regression model was created for this purpose.
RESULTS: Alcohol intake during pregnancy and medical ionizing radiation exposure were the most significant predictors of HC. The mothers' alcohol consumption increased with the mothers' and fathers' education level, net family income and fathers' alcohol consumption. In contrast, maternal smoking decreased with increasing mothers' and fathers' education level and net family income. About 13% of the surveyed embryos were exposed to illegal drugs.
CONCLUSIONS: Mild to moderate alcohol consumption diminishes the at-birth HC of theoretically healthy newborns in a linear form. There was no threshold dose. We perceived a need for increasing the awareness, and for training, of health care professionals and parents, in regard to risks of alcohol consumption and for recommending abstinence of these substances in both parents during pregnancy. It should also be remembered that medical ionizing radiation should be performed only during the first half of the cycle in fertile women. We think that our study has an important social impact as it affords data for implementing policies for promoting "healthy pregnancies".