Study objective -To test the stress hypothesis by characterising women during their first pregnancy who continue to smoke in early pregnancy in comparison with women who quit smoking, with special reference to psychosocial factors like social network, social support, demands, and control in work and daily life. Design -The study is based on a cohort of primigravidas followed during pregnancy. Data were collected by self administered questionnaires during the pregnant womens' first antenatal visit at about 12 weeks.Setting -The study was performed in the antenatal clinics in the city ofMalmo, Sweden.Participants -The participants were all primigravidas living in the city of Malmo, Sweden, over a one year period, 1991-92.A total of 872 (87.7%) of the 994 invited women agreed to participate. The population of this study on smoking includes all primigravidas who at the time of conception were smoking (n=404, 46.3%).Main results -At the first antenatal visit (63-6% (n =257) of the prepregnancy smokers were still smoking (a total smoking prevalence of 29-5%). The pregnant smokers were on average younger and had a lower educational level. The highest relative risk (RR) of continued smoking was found among unmarried women RR 2-7 (95% confidence interval) (1.5, 4.8), women having unplanned pregnancies RR 2-2 (1-2, 4.0) and those with a low social participation RR 1-6 (1.0, 2-7), low instrumental support RR 2-6 (1.2, 6.0), low support from the child's father RR 2-1 (1.0, 4.2) and those exposed to job strain RR= 2-3 (1.1,4-8). The In recent years great attention has been paid to the dangers of smoking during pregnancy. In spite ofthis, many pregnant women continue to smoke. In Sweden the prevalence of smoking among all pregnant women was 21 8% in 1992 (Swedish Medical Birth Registry -personal communication). A study from two big cities in Denmark showed a prevalence of 44% in 1987, and 81% ofthese women were still smoking at the end of pregnancy.9 One Norwegian study in 1989 showed a smoking prevalence of 46% 3 months before pregnancy, and 84% of the women were still smoking at the time of the first medical check up. '0 In a Swedish study, 32% of the pregnant women in one big city were daily smokers at the time of conception and by the time oftheir antenatal visit, 2 months later, 77% reported that they were still smoking."1 Women's smoking has been seen as related to social deprivation, stress, and disadvantage.2 13 Persistent smoking during pregnancy is found to be related to low household incomes, living in rented accommodation, being unmarried, and having a husband or partner in manual employment.'4 High parity number, not living with the infant's father, and daily passive smoking at home are also associated with an increased risk for continued smoking.'5 Other important predictors of unsuccessful smoking cessation are a high level of smoking before pregnancy and high coffee consumption.9Women experiencing depression and those with psychosocial difficulties in daily domestic roles also have higher rates of pe...