Smoking and pregnancy: the influence of maternal and gestational factors on the outcome of pregnancy and the newborn.

In this multivariate prospective case controlled study a total of 576 pregnancies were examined. Of the mothers 162 were light, 46 moderate and 80 ex-smokers, and 288 non-smokers. Forty variants of the mother, pregnancy, delivery and the newborn were taken in consideration. The mean gestational age in all study groups varied between 276-280 days, the maternal gestational weight gain between 12.2-14.7 kg. No difference was observed in maternal pre-pregnant weight and height. Light smokers' newborns' mean birth weight was 3396 g, moderate smokers' 3196, ex-smokers' 3516, and non smoking controls' 3577. When maternal size, gestational age and weight gain were standardised, smoking remained the only cause to explain the differences observed between smokers' and non-smokers' newborns' characteristics. No differences were observed between ex-smokers, women who stopped smoking during the first trimester of gestation, and non smoking controls.