Partner smoking influences whether mothers quit smoking during pregnancy: a prospective cohort study

ObjectiveTo analyse the prevalence and intensity of smoking among pregnant women and their partners, and factors associated with quitting smoking among pregnant women. DesignA prospective cohort study, starting in 2013. SettingAndalusia, the south of Spain. SampleA cohort of 486 healthy pregnant women followed-up on three occasions during pregnancy. MethodsEstimation of the proportions of women and partners who quit smoking at each trimester. Main outcome measuresTo determine factors associated in a multivariable model, considering sociodemographic, obstetric, anthropometric, lifestyle variables, and the smoking habits of their partners. ResultsA high proportion of women quit smoking during pregnancy (61.08%; 95% confidence interval, 95% CI 53.61-68.55%). The smoking rate amongst mothers decreased from 36.06% (n = 167) before pregnancy to 14.08% (n = 65), 12.39% (n = 54), and 11.92% (n = 51) during the three pregnancy trimesters (P < 0.001), and consumption decreased from 8.71 cigarettes/day in the first trimester to 5.51 cigarettes/day in the second trimester (P < 0.001) and 5.96 cigarettes/day in third trimester (P = 0.0002 first versus third trimester). There was only a minimal decrease in the frequency of smoking among the partners, however: 38.44% (n = 178) before pregnancy, and 36.07% (n = 167), 32.72% (n = 143), and 31.85% (n = 136) during the three trimesters of pregnancy. The consumption of cigarettes did not decrease among partners: 11.75, 11.67, and 12.09 cigarettes/day (P = 0.4299 first versus second trimester; P = 0.654 first versus third trimester). Women whose partner smoked were less likely to quit (adjusted odds ratio, aOR 0.26; 95% CI 0.12-0.55). ConclusionsAbout one in ten pregnant women smoked and one in four was a passive smoker. Strategies to reduce tobacco exposure in pregnancy should include a focus on partner smoking.