Use of medication in pregnancy on the rise: Study on 1.4 million Danish pregnancies from 1998 to 2018

Introduction: Maternal demographics have evolved, and more women than ever enter pregnancy with preexisting comorbidity and with potentially complex medication exposure, including polypharmacy (concomitant intake of multiple medications). This study aims to describe the evolution of medication use in pregnancy in Denmark from 1998 to 2018 with special focus on polypharmacy, patterns of use, and underlying demographics. Material and methods: A Danish nationwide historical registry study based on all clinically recognized pregnancies with a gestation >= 10 weeks between 1998 and 2018. Medication use was estimated by redemption of prescriptions during pregnancy. Results: Among a total of 1 402 327 clinically recognized pregnancies, redemption of at least one prescription medication during pregnancy increased from 56.9% in 1998 to 63.3% in 2018, coinciding with an increased use of polypharmacy (from 24.8% in 1998 to 35.2% in 2018). The prevalence of pregnant women who used medications for chronic conditions increased more than the prevalence of women treated for occasional or short-time conditions. Redemption of one or multiple prescription medications during pregnancy was mostly seen among pregnant women >= 35 years of age. However, pregnant women <25 years old exhibited the largest increase in medication use during the study period. Conclusions: Medication use in general, and polypharmacy in particular, increased from 1998 to 2008, possibly as the result of an increased prevalence of pregnant women with chronic conditions requiring pharmacological treatment. Notably, a marked maternal age-based discrepancy in usage pattern was observed, highlighting the need for further research in this area. The rise in the prevalence of polypharmacy during pregnancy underscores the need for pharmacovigilance to monitor adverse effects. Future studies should investigate the patterns of polypharmacy and the accompanying maternal and fetal risks.