Social and obstetric features associated with smoking in pregnancy.

The smoking habits of 2000 consecutive pregnant women have been analysed in relation to their race, social features and obstetric results. Only 60% of white patients were non-smokers compared with 80% of blacks and 90% of Asians, and whereas 20% of white patients smoked heavily only 3% of blacks or Asians did. Smokers booked later and were more frequently unsure of their dates, unemployed, unmarried and defaulters from the antenatal clinic. The incidence of antepartum haemorrhage was doubled amongst the heavy smoking multigravid patients in spite of a slightly decreased incidence of hypertensive disease. More non-smokers required induction of labour for raised blood pressure, and more smokers for fetal distress. The most significant differences between the smokers and non-smokers were the decrease in mean birth-weight associated with increased smoking (3.31 kg for non-smoking primigravidae compared with 3.14 kg for heavy smokers) and the threefold increased incidence of small-for-dates babies amongst the heavy smokers. There was no significant difference in the perinatal mortality.