Trends in the prevalence of polypharmacy during pregnancy in the UK 2000–2019

Objective: Medication use during pregnancy has increased over the past few decades in high income countries. Few studies have looked at the prevalence of multiple medication use amongst pregnant women, and none have considered the prevalence in pregnant women with multimorbidity. The aim of this study is to describe the trend in the prevalence of polypharmacy in pregnancy (here defined as the prescrip-tion of two or more medications) between 2000 and 2019, the prevalence of polypharmacy in pregnancy in women with multimorbidity in 2019 and the medications and pairs of medication most commonly prescribed.

Design: A population based retrospective cohort study of pregnancies was conducted between 2000 and 2019 using the pregnancy register developed using Clinical Practice Research Datalink (CPRD), a UK primary care database.

Method: We included pregnancy records of women aged 15–49. All medications prescribed within CPRD general practices were classified into a list of 577 medication categories based on their assigned British National Formulary chapters.Yearly prevalence of polypharmacy during the first trimester was calculated. For the 2019 cohort of pregnancies, the prev-alence of polypharmacy in women with pre-existing active multimorbidity (defined as the presence of two or more ac-tive long-term health conditions) was calculated. Medication commonly prescribed and pairs of medication commonly co-prescribed were identified.

Results: Data were available for 812,354 pregnancies between 2000 and 2019. The mean age of women was 28.7 (sd 6.0).The prevalence of polypharmacy was 18.9% (95% CI 18.4– 19.4%), 24.7% (95% CI 24.3–25.0%) and 31.6% (95% CI 30.7– 32.6%) in 2000, 2009 and 2019 respectively. In 2019, the prevalence of polypharmacy during the first trimester for women with multimorbidity was 57.1% (95% CI 55.0–59.2%).Between 2000 and 2019, the three most common medications prescribed during the first trimester were broad-spectrum penicillin (6.6% of pregnancies) compound analgesics (4.5%) and drugs for the treatment of candidiasis (4.3%). During the first trimester, the most common pairs of medications prescribed to manage different long-term conditions in pregnant women with active multimorbidity were SSRI and selective beta two agonists (1.8%), topical corticosteroids and selective beta two agonists (1.4%), and corticosteroids used in nasal allergy and selective beta two agonists (1.3%).

Conclusion: Prevalence of polypharmacy during pregnancy has increased over the past two decades and is particularly high in women with multimorbidity. Well-conducted pharmaco-epidemiological research is needed to understand the com-bined effects of prescribed medications on the developing fetus.