Design and methods: A cross-sectional study using linkage of Swedish population and health registers. The Swedish National Patient Register encompasses inpatients and outpatients. Inpatient data in Sweden is available nationwide since 1987. Outpatient diagnoses from hospitals started to be collected in 1997. Data in the Patient Register will be linked to the Swedish Medical Birth Register (MBR) at the National Board of Health and Welfare through the unique personal identity number assigned to all Swedish residents, Exposed women: Mothers who had given birth to a child as a result of IVF will be retrieved from the Swedish IVF Register at the National Board of Health and Welfare. The Swedish IVF Register is now a part of the Swedish Medical Birth Register (MBR) at the National Board of Health and Welfare and includes information on IVF pregnancies since 1982.