PS25 Discontinuation of Antiepileptic Drugs in Pregnancy: A UK Population Based Study in the Health Improvement Network (THIN)

Abstract

Purpose: Antiepileptic drugs (AEDs) control seizures, which is a priority in pregnancy to prevent harm to the mother and fetus. However, AEDs are associated with increased risk of congenital malformations. We examined the discontinuation of AED prescribing in pregnant women using UK primary care data from The Health Improvement Network. Method: In total, 174,055 pregnant women were identified aged 13- 55 years of which 745 were prescribed AEDs for epilepsy in the three months before pregnancy. Time to the last consecutive AED prescription before delivery was estimated and comparisons made to non-pregnant women with epilepsy, using Cox's regression. Factors predicting discontinuation of AEDs amongst pregnant women were investigated. Result: Pregnant women with epilepsy were twice as likely to cease AEDs compared to non-pregnant women (Hazard Ratio (HR):2.00, 95% confidence interval (CI):1.62-2.47). Of 745 women, 601 (80.7%) continued treatment into pregnancy and 465 (62.4%) to the end of the second trimester. Of 1490 non-pregnant women with epilepsy, 1242 (83.4%) and 1071 (71.9%) continued for comparable time periods. Compared to pregnant women with more than one AED prescribed in 3-6 months before pregnancy, women with one prescription were more likely to cease treatment (HR: 3.31, 95% CI: 2.57-4.23), whilst those with no prior prescriptions were at an even higher risk (HR: 6.32, 95% CI: 4.57-8.73). Conclusion: Pregnancy is a determinant for the discontinuation of AED prescribing amongst women with epilepsy, despite the possible grave consequences of uncontrolled seizures in pregnancy. Women with little exposure to AEDs prior to pregnancy should be monitored closely to ensure they do not abruptly cease medication.