Smoking habits of 597 pregnant women were investigated; 48.6% of the women smoked during pregnancy. Percentile birth weight proved to be decreased compared with the Amsterdam birth weight charts. This decrease could be attributed largely to smoking in pregnancy. Mean birth weight was significantly lower in smokers than in nonsmokers (230 g; p < 0.01). Placental weight and menstrual age were not affected by smoking during pregnancy. A statistically significant higher incidence of hypertension in pregnancy in the nonsmokers group compared with the smokers group (p < 0.05) was established.