Background Women with schizophrenia and bipolar disorder are at a higher risk of obstetric and neonatal complications. The aim of this study was to better understand the factors that may influence these adverse outcomes. Method We examined obstetric and neonatal outcomes of pregnant women with schizophrenia and bipolar disorder and factors possibly influencing these outcomes. A retrospective review of the medical history of 112 women with a DSM-IV diagnosis of schizophrenia or bipolar disorder was undertaken. Data for controls were extracted from the hospital s electronic birth record data. Results Women with schizophrenia and bipolar disorder presented later for their first antenatal visit and had higher rates of smoking and illicit drug use than the control group. They also had higher rates of pre-eclampsia and gestational diabetes. Their infants were less likely to have Apgar scores 8?10 at both 1 and 5 minutes and were more likely to be admitted to special care/neonatal intensive care nursery than the infants of controls. The rate of pre-term birth was significantly increased in the women with schizophrenia and bipolar disorder. Pre-term birth and admission to special care/neonatal intensive care were predicted by smoking and illicit drug use. Conclusion These data point to potentially modifiable factors as significant contributors to the high rate of adverse obstetric and neonatal outcomes in women with mental illness. Comprehensive management of women with mental illness prior to, during pregnancy and in the postnatal period may have long-term benefits for their offspring.