Nationwide register-based surveillance system on drugs and pregnancy in Finland 1996-2006.

PURPOSE: The aim of this population-based nationwide drugs and pregnancy surveillance system was to get basic information on the use of prescribed drugs during pregnancy and to achieve more detailed information on drug exposure-outcome associations with data obtained from the Finnish national health registers.
METHODS: The data are based on information on all pregnancies ending in births (n = 632,629) or termination of pregnancy (TOP) (n = 117,255) in Finland between 1996 and 2006. The data containing information on maternal background factors, chronic diseases and drug purchases during pregnancy, born children, induced abortions, perinatal health and major congenital malformations were obtained from the Finnish national health registers. Information from the different registers was merged through record linkages based on unique personal identification numbers. Statistical analyses were conducted between the exposed and unexposed for individual drugs or Anatomical Therapeutic Chemical (ATC) classification drug groups in multivariate logistic regression including potential confounding factors.
RESULTS: Nearly half of parturients and almost every third woman with TOP purchased drugs at least once 1 month prior to pregnancy and/or during pregnancy. The most frequent chronic diseases during pregnancy were asthma, hypothyroidism, epilepsy, rheumatoid arthritis and diabetes. Previously known causal connections between maternal chronic diseases and/or medication and perinatal health risks were already seen in the ATC-group-level analysis.
CONCLUSIONS: Comprehensive and detailed information for pharmacoepidemiological research on the effects of drug use during pregnancy in a cohort setting is possible with long-term and cumulative data collection.