How well does epidemiological evidence hold for the relationship between smoking and adverse obstetric outcomes in New South Wales?

This study examines whether the established epidemiological relationship between cigarette-smoking exposure in pregnancy and adverse obstetric outcomes are confirmed in Australian data from the NSW Midwives Data Collection (MDC). These data were analysed to compare the obstetric complications and pregnancy outcomes between smoking and nonsmoking women confined in 1994. Results showed that smoking mothers had higher rates of antepartum haemorrhage due to placental abruption and placenta praevia. They were also at higher risk of giving birth to low birth-weight babies and preterm delivery. Infants born to smoking mothers were 17% more likely to be admitted to hospital special care nurseries or neonatal intensive care units. Moreover, the risk of reported perinatal death among babies of smoking mothers was 20% higher than babies of nonsmoking mothers. However, smoking during pregnancy was found to confer a protective effect against the development of pregnancy-induced hypertension. These results were compared with existing evidence from the literature. Published research reports on the corresponding smoking effects were identified to assess the consistency of evidence and typical risk ratios. Findings from the literature search showed a near-perfect concordance with the associations in the NSW MDC data. The paper documents the likely complications which might be prevented if smoking in pregnancy were eliminated. There remains a real need for effective programmes to reduce smoking prevalence in pregnancy.