BACKGROUND Worldwide the prevalence of neuropsychiatric illness among women of reproductive age is higher than ever before. This study investigates the influences of maternal substance abuse/dependence and neuropsychiatric illness on pregnancy and neonatal outcomes. METHODS Using a retrospective study design 185 pregnancies in women with neuropsychiatric illnesses or substance abuse were identified at a single centre over a period of 3.25 years and compared to 4907 pregnancies in healthy women without mental illness. Differences in pre-, peri- and postnatal pregnancy parameters were studied. RESULTS Numbers of previous abortions on obstetric history were significantly higher in cases compared to controls, women with depression being especially affected. The number of antenatal visits was also higher among cases, especially in women with depression. The caesarean section rate was significantly higher in cases compared to controls. Children of women with neuropsychiatric illness were born at lower gestational ages than those of healthy control mothers, however there were no significant differences between case and control groups for birth weight, head circumference or Apgar scores. Some isolated differences were found for disease-specific case subgroups compared to controls. CONCLUSIONS The study shows a relationship between maternal neuropsychiatric illness and pregnancy outcomes independent of medication use. Rates of spontaneous abortion were higher. Children were born earlier, yet the neonatal outcomes birth weight, head circumference and Apgar score were not worse than children of mentally healthy women.