Trends in prescription drug use during pregnancy and postpartum in Norway, 2005 to 2015.

PURPOSE: To explore trends in use of maternal medication 3 months prior to, during and 3 months after pregnancy.

METHODS: Data on births from the Medical Birth Registry of Norway were linked to the Norwegian Prescription Database, identifying women's use of medications around pregnancy. All women giving birth in Norway during 2005 to 2015 (638 532 singleton births to 414 567 women) were included. Proportions of pregnant women using different medications in association with pregnancy, and annual relative change in medication use during 2005 to 2015, were calculated.

RESULTS: In Norway, 60% of pregnant women used prescription medications during pregnancy (2005-15), increasing from 57% in 2005 to 62% in 2015. The annual relative increase was 0.9% (95% CI: 0.8-1.0). In the first trimester, approximately 17% of the women used medications regarded as potentially teratogenic during 2005 to 2015, increasing from 15% to 19%. Overall, this proportion was higher in the first than in the second (8.9%) and third (8.0%) trimesters, and higher than in the 3 months after pregnancy (14%). The annual relative increase of medications regarded as potentially teratogenic in the first trimester was 2.5% (95% CI: 2.3-2.7).

CONCLUSIONS: The proportion of women using potentially teratogenic medications in the first trimester of pregnancy have increased during the last decade. Clinicians need to be aware of the possibility of pregnancy when prescribing potentially teratogenic medication to women of fertile age and focus this in the consultations. The increasing trends call for the need of routine surveillance of adverse birth outcomes linked to medication use in pregnancy.