(B-307) Prevalence of Adverse Pregnancy Outcomes Associated with First-Trimester Antiepileptic Drug Exposure: Evidence from a Cohort Study in the US.

Background: Antiepileptic drug (AED) treatment during pregnancy presents challenges, as discontinuation increases the risk of uncontrolled seizures and harm to both the mother and the unborn baby while exposure to AED is associated with risks of structural and neurodevelopmental teratogenic effects. Due to the increasing prevalence of AED use among women of childbearing age, real-world safety studies are imperative to assess impact on pregnancy and fetal outcomes.

Objectives: Using a large, representative, closed-claims database in the United States (Oracle US Claims), this study aimed to identify pregnancy episodes with AED exposure in the first trimester (T1) and describe adverse pregnancy outcomes.

Methods: Data from the Oracle US Claims were analyzed retrospectively for the period July 2022 to July 2023. Pregnancy episodes among ages 15–49 years were identified. Validated diagnosis and procedure code algorithms were applied to estimate gestational age and trimesters and to identify adverse outcomes (preterm birth (PTB), stillbirth (SB) and spontaneous abortion (SA)). Prescription reimbursement codes were used to identify exposure to 1st generation and selected newer AEDs during T1.

Results: 526,947 pregnancy episodes were included, of which 13,735 (2.6%) were identified to have at least 1 prescription claim code for an AED (AED-exposed).
Among AED-exposed pregnancies, median maternal age was 31 years and prevalence of PTB, SB, and SA were 5.1% (N=700), 0.9% (N=120), and 25.3% (N=3,472) respectively.
Among AED-exposed pregnancies, the most prescribed 1st generation drug was Clonazepam for 1,455 (10.6%) pregnancies. The most prescribed new generation AED was Gabapentin for 3,030 (22.1%) pregnancies.
Among Gabapentin-exposed pregnancies, prevalence of PTB, SB and SA were 4.7% (N=142), 0.8% (N=25) and 21.2% (N=644), respectively.
Among Clonazepam-exposed pregnancies, prevalence of PTB, SB and SA were 3.6% (N=52), 0.3% (N=5) and 18.9% (N=274), respectively.

Conclusions: This research applied validated algorithms in an accurate and representative real-world dataset to robustly identify pregnancy episodes with AED-exposure during T1 and associated adverse pregnancy outcomes. These findings highlight and confirm the imperative for further evaluation of AED safety during pregnancy, particularly real-world trends in prescribing patterns over time and across various AED generations, considering real-world evidence-based practice guidelines.