Outcomes of pregnancy in women using illegal drugs and in women who smoke cigarettes

Objective
To compare obstetric outcomes in women using illegal drugs with women who smoke cigarettes.

Design
Retrospective cohort study.

Setting
Aberdeen, UK.

Population
All deliveries in Aberdeen in women using illegal drugs and women who smoked cigarettes during 1997–2007.

Material and methods
The women who used illegal drugs were identified from a database of affected pregnant women in Aberdeen. The Aberdeen Maternity and Neonatal Databank was used to identify women who smoke cigarettes and to obtain pregnancy outcome information. Sociodemographic characteristics, maternal and perinatal outcomes were compared using chi-squared test, independent sample t-test and logistic regression analysis.

Main outcome measures
Preterm delivery, low birthweight (standardized birthweight score <-2) and admission to the neonatal unit.

Results
Of the 561 illegal drug users, 96% were also cigarette smokers. Compared with women who smoke cigarettes with no reported illegal drug use, they were significantly more likely to have a preterm delivery [adjusted odds ratio (aOR) 1.6 (95% confidence interval (CI) 1.3–2.1)], low birthweight baby [aOR 1.9 (95%CI 1.4–2.6)], baby admitted to the neonatal unit [aOR 13.3 (95%CI 10.9–16.3)], deep vein thrombosis [aOR (95%CI 8.8–50.8)] and antepartum hemorrhage [aOR (95%CI 1.2–2.1)]. They were less likely to be at the extremes of age, or to develop pregnancy-induced hypertension [aOR 0.3 (95%CI 0.2–0.4)].

Conclusion
Illegal drug use in pregnancy appears to increase the risk of adverse outcomes, over and above that related to cigarette smoking, but appears to be associated with lower prevalence of gestational hypertension.