Substance use during pregnancy: risk factors and obstetric and perinatal outcomes in South Australia

OBJECTIVE: To determine the prevalence of self-reported substance use during pregnancy in South Australia, the characteristics of substance users, their obstetric outcomes and the perinatal outcomes of their babies. METHODS: Multivariable logistic regression with STATA statistical software was undertaken using the South Australian perinatal data collection 1998-2002. An audit was conducted on every fifth case coded as substance use to identify the actual substances used. RESULTS: Substance use was reported by women in 707 of 89 080 confinements (0.8%). Marijuana (38.9%), methadone (29.9%), amphetamines (14.6%) and heroin (12.5%) were most commonly reported, with polydrug use among 18.8% of the women audited. Substance users were more likely than non-users to be smokers, to have a psychiatric condition, to be single, indigenous, of lower socio-economic status and living in the metropolitan area. The outcome models had poor predictive powers. Substance use was associated with increased risks for placental abruption (OR 2.53) and antepartum haemorrhage from other causes (OR 1.41). The exposed babies had increased risks for preterm birth (OR 2.63), small for gestational age (OR 1.79), congenital abnormalities (1.52), nursery stays longer than 7 days (OR 4.07), stillbirth (OR 2.54) and neonatal death (OR 2.92). CONCLUSIONS: Substance use in pregnancy is associated with increased risks for antepartum haemorrhage and poor perinatal outcomes. However, only a small amount of the variance in outcomes can be explained by the substance use alone. Recent initiatives to improve identification and support of women exposed to adverse health, psychosocial and lifestyle factors will need evaluation.