OBJECTIVES: Insight into comorbidities and detailed drug exposure before and during pregnancies as well as outcomes in children is pivotal to perform pharmacoepidemiological pregnancy outcome studies. A database was constructed that captures both detailed drug exposure before and during pregnancy as well as pregnancy related information and outcomes of the neonate (and other relevant clinical information) by linking the Netherlands Perinatal Registry (PRN) with the PHARMO Record Linkage System (RLS). METHODS: The PRN is an anonymous nationwide registry, including data from the midwifery, the obstetrics and the neonatology/pediatrics registry. The PHARMO RLS includes data from multiple healthcare databases such as drug dispensings, hospitalizations, GP data and clinical laboratory measurements and covers approximately 20% of the Dutch population. Both databases were linked using different record linkage techniques. Key variables (e.g. maternal age, gestational duration, parity, singleton birth) were assessed to determine  comparability between  the PRN and the linked PRN-PHARMO RLS pregnancies. RESULTS: The linkage of 1,453,504 pregnancies registered between 2000 and 2007 in the PRN with PHARMO RLS resulted in a cohort of 151,250 women with complete drug and clinical data available for 203,972 pregnancies. Linked pregnancies were comparable with all pregnancies. In 67% of all pregnancies at least one prescription drug was used. The most frequently used drugs included anti-anemic preparations (26%), antibacterials (20%) and gynecologic anti-infectives (14%). As dispensing date, duration of use and dose are recorded in the PHARMO RLS, exposure per trimester can be assessed and related to birth outcomes, such as prematurity and congenital defects as recorded in the PRN. CONCLUSIONS: Linkage of the Netherlands Perinatal Registry and the PHARMO RLS creates the possibility to study detailed drug utilization and comorbidities of mothers before, during and after pregnancy and of children. This enables to study potential adverse effects that might impact pregnancies or child development later in life.