OC 35.5 - Epidemiology of antithrombotic therapy during pregnancy in The Netherlands (2013-2019)

Background: Recent/large-scale investigations into antithrombotic therapy during pregnancy are absent.

Aims: To update epidemiology of antithrombotic therapy during pregnancy, including prescription patterns, maternal outcomes, and their time trends.

Methods: Dutch prenatal registry (including data on all pregnancies with a gestational age ≥22 weeks) was linked to nationwide registries from Statistics Netherlands (containing outpatient medication prescriptions, hospital diagnoses, and mortality). Antithrombotic therapy before and during pregnancies, and maternal outcomes during pregnancies and postpartum periods were determined and compared by calendar years.

Results: 1,122,711 pregnancies (of 822,115 women) between 2013 and 2019 were included (30.5±4.7 years old; 78.9% Caucasian). 0.4% (n=3,983) had ≥1 anticoagulant prescription within six months before pregnancies, where the majority was low-molecular-weight heparin (LMWH, ≈80%). This increased to 1.1% (n=12,519) during pregnancies, and LMWH remained the majority (>97%), while only 97 and 446 pregnancies had ≥1 prescription of direct oral anticoagulant or vitamin K antagonist, respectively. For antiplatelet, 0.2% (n=2,547) received it before pregnancies, which increased to 2.3% (n=25,715) during pregnancies. Noticeably, both LMWH and antiplatelet had been increasingly prescribed since the 5th-8th week, where DOAC and VKA use decreased, especially for prior users (Figure 1). Between calendar years, the pregnancies showed similar baseline characteristics and antithrombotic agent use both before and during pregnancies, except antiplatelet use during pregnancies increased from 0.8% in 2013 to 5.7% in 2019. For maternal outcomes, those who received antithrombotic therapy during pregnancies showed significantly higher incidence of both bleeding and thromboembolism than those who did not, but no notable time trends in incidence of these outcomes were observed (Table 1). An extra analysis found the incidence of preeclampsia/eclampsia during pregnancies decreased to 2.3% in 2019 after reaching the peak (2.5%) in 2015.

Conclusion(s): The Dutch pregnant population in recent years saw broadly constant anticoagulant use and maternal outcomes (i.e., bleeding and thromboembolism), but an increase in antiplatelet use.