An understanding of the epidemiology of alcohol and drug use in young women is important to appreciate the considerable morbidity and mortality associated with it and to understand the impact of such use on offspring. Although abstention rates are consistently higher among women than men in general substance misuse is increasing in young women. Differences in definitions, measurement techniques, availability, social acceptability and affordability partly explain the great variability in reported prevalence rates. Alcohol exposure among pregnant women varies from 0.2% to 14.8%. An Australian national survey revealed that nearly half of pregnant and / or breast-feeding women up to 6 months postpartum were using alcohol. A Swedish study reported risky use of alcohol during the first 6 weeks of pregnancy, at 15%. Cannabis use among pregnant women varies from 1.8% to 15%. The reported prevalence of opiate use during pregnancy ranges from 1.65% to 8.5%. Cocaine use among pregnant women is reported to be between 0.3% and 9.5%. Most pregnant women stop or reduce their substance use during pregnancy and this might be an opportune moment for detection and treatment. Substance use tends to increase sharply in the postpartum period with adverse consequences for mother and baby. Perinatal substance misuse interventions can reduce adverse neonatal outcomes. On the basis of the relatively high rate of substance use disorders during pregnancy and postpartum period, effective screening and intervention strategies should be implemented.