Recent cessation of smoking and its effect on pregnancy outcomes.

Background: Smoking in pregnancy is associated with a range of adverse pregnancy outcomes.

Objective: To compare adverse pregnancy outcomes for women according to smoking status at the first antenatal visit in an Australian setting.

Methods: A retrospective study using routinely collected data of all births between 1997 and 2006 at the Mater Mothers' Hospital Brisbane (MMH). Analysis was undertaken using multivariate logistic regression. The following comparisons were undertaken: (i) smokers versus non-smokers; (ii) recent quitters (quit within the last 12 months) versus smokers; and (iii) recent quitters versus non-smokers. Primary outcome measures were small for gestational age (SGA) <10th customised centile and preterm birth (PTB) <37 weeks.

Results: Between 1997 and 2006, 40,193 women birthed at the MMH. Of these 30,524 (75.9%), for which adequate data were available, were included in the study. The smoking rate at booking was 15.4%. Compared to non-smokers (n = 25,814), women who were smoking at the first visit (n = 4710) were at increased risk of SGA (aOR = 2.26, 95%CI = 2.08-2.47) and PTB (aOR = 1.42, 95%CI = 1.27-1.59). In the subset (7801 births) used for comparisons two and three, compared to smokers (n = 1434), recent quitters (n = 945) were at a decreased risk of SGA (aOR = 0.43, 95%CI = 0.33-0.57) but not PTB (aOR = 0.92. 95%CI = 0.69-1.23). Outcomes for recent quitters and non-smokers (n = 5422) appeared similar.

Conclusions: This study confirms the increased risk of continued smoking in pregnancy. Women who quit prior to or during early pregnancy appear to have similar risk to that of non-smokers.