OC 31.5 - Time trends (2013-2019) in antithrombotic therapy prescriptions and thromboembolic complications during the postpartum period in the Netherlands: a nationwide study

Background: Reliable population-based data on antithrombotic therapy and thrombotic events in the postpartum period are scarce.

Aims: To describe time trends in antithrombotic therapy prescriptions and thrombotic complications during the postpartum period in the Netherlands.

Methods: Data from the Dutch perinatal registry (compulsory to register for deliveries ≥22 gestational weeks) were linked to nationwide data on population/healthcare utilization from Statistics Netherlands. All women aged 16-45 years in the registry whose pregnancies started between 2013 and 2019 were included. After classification into cohorts of the year in which the pregnancy started (2013 to 2019), the women were followed for six weeks postpartum. Data on outpatient medication prescriptions and in-hospital diagnoses were used to determine proportions of receiving antithrombotic therapy [i.e., low-molecular-weight heparin (LMWH), vitamin K antagonists, direct oral anticoagulants, and antiplatelet agents] and risk of venous thromboembolism (VTE) or arterial thrombotic (ischemic stroke, arterial embolism, myocardial infarction) events. Hazard ratios (aHR) were estimated by multivariable Cox regression (adjusting for maternal baseline characteristics, pregnancy complications, and antithrombotic therapy during pregnancy) to compare risks of clinical events between years.

Results: A total of 1,122,702 women were included (maternal age 31.3±4.7 years; median gravidity 2 (1-3), parity 1 (0-1); gestational age 39.4±2.0 weeks), with a stable caesarean section rate (16.0%) over years. During the postpartum period, the proportion of women receiving LMWH increased from 1.0% in 2013 to 1.6% in 2019, while the proportions of receiving other antithrombotic medications remained low (all < 0.1% in 2019, Figure-1). VTE risk decreased from 0.63/1000 in 2013 to 0.33/1000 in 2019 (aHR=0.55, 95%CI 0.39-0.77). Risk of arterial thromboembolic complications remained low and constant over the years ( < 1 per 100,000; aHR=1.11, 95%CI 0.51-2.44, Figure-2).

Conclusion(s): From 2013 to 2019 LMWH was increasingly prescribed to postpartum women in the Netherlands, and postpartum VTE incidence decreased.