Objective: To examine the influence of continued smoking and previous pregnancy outcomes on subsequent pregnancy outcomes.
Design: Retrospective descriptive epidemiological study.
Setting: New South Wales, Australia, 1994-2004.
Population: Mothers who delivered two consecutive singleton births.
Methods: Bivariate and multiple logistic regression analyses were used to explore the influence of continued smoking on subsequent pregnancy outcomes.
Main outcome measures: Subsequent preterm birth (PTB), low birthweight (LBW) and perinatal deaths.
Results: The findings showed that in addition to maternal and neonatal characteristics, birth outcomes in subsequent pregnancies were affected by poor birth outcomes in previous pregnancy. Previous PTB, short birth interval, antenatal care, gestational diabetes and smoking habits in two successive pregnancies had relatively strong association with a subsequent PTB and LBW. Mothers who continued to smoke in subsequent pregnancies were more likely to have adverse pregnancy outcomes compared with others. A change from smoking in first pregnancy to not smoking in next pregnancy had reduced the chance of a subsequent PTB and LBW. The risk of a subsequent preterm and LBW delivery increased with the amount of smoking during the second pregnancy. For mothers who remain as moderate smokers in subsequent pregnancies, the odds ratios for a PTB and LBW delivery were significantly lower than those who remain as heavy smokers.
Conclusions: Effective interventions to help women to stop smoking during pregnancy could reduce the risk of adverse obstetric and pregnancy outcomes. Strategies to reduce the prevalence of smoking during pregnancy may include intense intervention for women who have had smoking-related adverse outcomes in a previous pregnancy.