The impact of Aboriginal status, cigarette smoking and smoking cessation on perinatal outcomes in South Australia

Objective: To assess the impact of Aboriginal status, active cigarette smoking and smoking cessation during pregnancy on perinatal outcomes. Design: Retrospective cohort study from 1 January 1999 to 31 December 2008. Setting: All singleton births in South Australia. Participants: Population-based birth records of pregnancies to Aboriginal women (n = 4245) and non-Aboriginal women (n = 167746). Main outcome measures: Adjusted odds ratios (aORs) and 95% CIs for adverse maternal and neonatal outcomes according to Aboriginal status and maternal smoking in pregnancy. Results: Active cigarette smoking during pregnancy was associated with an increased risk of adverse perinatal outcomes, including premature labour (Aboriginal, 1-10 cigarettes per day: aOR,1.69; 95% CI, 1.28-2.23; non-Aboriginal, 1-10 cigarettes per day: aOR, 1.46; 95% CI, 1.34-1.58), preterm birth (Aboriginal, 1-10 cigarettes per day: aOR, 1.40; 95% CI, 1.14-1.73; non-Aboriginal, 1-10 cigarettes per day: aOR,1.48; 95% CI, 1.39-1.57), intrauterine growth restriction (Aboriginal, 1-10 cigarettes per day: aOR, 2.33; 95% CI, 1.77-3.08; non-Aboriginal, 1-10 cigarettes per day: aOR, 2.65; 95% CI, 2.48-2.83) and small for gestational age (Aboriginal, 1-10 cigarettes per day: aOR, 2.49; 95% CI, 2.06-3.00; non-Aboriginal, 1-10 cigarettes per day: aOR, 2.29; 95% CI, 2.20-2.40). For both Aboriginal and non-Aboriginal women who smoked 11 or more cigarettes per day the aOR for these outcomes increased. Smoking cessation in the first trimester reduced these risks to levels comparable with non-smokers. The risk of each adverse outcome was greater in Aboriginal than non-Aboriginal women for all smoking categories; however, interactions between Aboriginal status and smoking were not significant, indicating an equal contribution of smoking to poor outcomes in both populations. Conclusions: Smoking cessation or reduction during pregnancy would significantly improve outcomes in both Aboriginal and non-Aboriginal women. This should be made a clear priority to improve pregnancy outcomes for all women.