Prevalence trends and individual patterns of antiepileptic drug use in pregnancy 2006-2016: A study in the five Nordic countries, United States, and Australia.

PURPOSE: To describe recent international trends in antiepileptic drug (AED) use during pregnancy and individual patterns of use including discontinuation and switching. METHODS: We studied pregnancies from 2006 to 2016 within linked population-based registers for births and dispensed prescription drugs from Denmark, Finland, Iceland, Norway, Sweden, and New South Wales, Australia and claims data for public and private insurance enrollees in the United States. We examined the prevalence of AED use: the proportion of pregnancies with ≥1 prescription filled from 3 months before pregnancy until birth, and individual patterns of use by trimester. RESULTS: Prevalence of AED use in almost five million pregnancies was 15.3 per 1000 (n = 75 249) and varied from 6.4 in Sweden to 34.5 per 1000 in the publicly-insured US population. AED use increased in all countries in 2006-2012 ranging from an increase of 22% in Australia to 104% in Sweden, and continued to rise or stabilized in the countries in which more recent data were available. Lamotrigine, clonazepam, and valproate were the most commonly used AEDs in the Nordic countries, United States, and Australia, respectively. Among AED users, 31% only filled a prescription in the 3 months before pregnancy. Most filled a prescription in the first trimester (59%) but few filled prescriptions in every trimester (22%). CONCLUSIONS: Use of AEDs in pregnancy rose from 2006 to 2016. Trends and patterns of use of valproate and lamotrigine reflected the safety data available during this period. Many women discontinued AEDs during pregnancy while some switched to another AED.