Longitudinal cohort survey of women's smoking behaviour and attitudes in pregnancy: study methods and baseline data

OBJECTIVES: To report the methods used to assemble a contemporary pregnancy cohort for investigating influences on smoking behaviour before, during and after pregnancy and to report characteristics of women recruited. DESIGN: Longitudinal cohort survey. SETTING: Two maternity hospitals, Nottingham, England. PARTICIPANTS: 3265 women who attended antenatal ultrasound scan clinics were offered cohort enrolment; those who were 8–26 weeks pregnant and were currently smoking or had recently stopped smoking were eligible. Cohort enrollment took place between August 2011 and August 2012. PRIMARY AND SECONDARY OUTCOME MEASURES: Prevalence of smoking at cohort entry and at two follow-up time points (34–36 weeks gestation and 3 months postnatally); response rate, participants’ sociodemographic characteristics. RESULTS: 1101 (33.7%, 95% CI 32.1% to 35.4%) women were eligible for inclusion in the cohort, and of these 850 (77.2%, 95% CI 74.6% to 79.6%) were recruited. Within the cohort, 57.4% (N=488, 95% CI 54.1% to 60.7%) reported to be current smokers. Current smokers were significantly younger than ex-smokers (p<0.05), more likely to have no formal qualifications and to not be in current paid employment compared to recent ex-smokers (p<0.001). CONCLUSIONS: This contemporary cohort, which seeks very detailed information on smoking in pregnancy and its determinants, includes women with comparable sociodemographic characteristics to those in other UK cross-sectional studies and cohorts. This suggests that future analyses using this cohort and aimed at understanding smoking behaviour in pregnancy may produce findings that are broadly generalisable.