Change in smoking status during two consecutive pregnancies: A population-based cohort study

Abstract

Objective: To investigate changes in tobacco smoking in two consecutive pregnancies and factors associated with the change. Design: Population-based cohort study. Setting: New South Wales, Australia, 2000-2010 Population: 183,385 women having first and second singleton pregnancies. Methods: Descriptive and multivariable logistic regression analyses of perinatal data linked to hospital admission data. Main outcome measures: Proportion of women smoking during their first pregnancy who quit by their second, and of women not smoking in their first pregnancy who did smoke during their second. Results: Among 22,761 smokers in the first pregnancy, 33.5% had quit by their second. Among 160,624 non-smokers in their first pregnancy, 3.6% smoked during their second. Women who aged ≥25 years, were married, born in a non-English speaking country, used private obstetric care, and lived in a socio-economically advantaged area were more likely to quit or less likely to start smoking in the second pregnancy. Smokers who had gestational hypertension (adjusted odds ratio and 95% confidence interval: 1.36, 1.23-1.51), a large-for-gestational-age infant (1.66, 1.46-1.89), and a stillbirth (1.44, 1.06-1.94) were more likely to quit, whereas smokers whose infant was small-for-gestational-age (0.65, 0.60-0.70) or admitted to special care nursery (0.87, 0.81-0.94) were less likely to quit. Among non-smokers in the first pregnancy, the risk of smoking in second pregnancy increased with late antenatal attendance (e.g. ≥26 weeks, 1.30, 1.14-1.48), gestational diabetes (1.25, 95%CI 1.07-1.45), preterm birth (e.g. spontaneous 1.25, 1.10-1.43), caesarean section (e.g. 2 prelabour 1.13, 1.01-1.26), and infant small-for-gestational-age (1.37, 1.26-1.48) or required special care nursery (1.14, 1.06-1.23). Inter-pregnancy interval of ≥3 years was associated with either change in smoking status. Conclusions: Most smokers continue to smoke in their next pregnancy, even among those who experienced poor outcomes. Intensive interventions should be explored and offered to women at the highest risk.