Malformation risk of new anti-epileptic drugs in women with epilepsy; observational data from the Kerala registry of epilepsy and pregnancy (KREP).

Objectives: We aim to report the major congenital malformation (MCM) rates for new and old anti-epileptic drugs (AED) exposures during the first trimester of pregnancy in women with epilepsy (WWE).

Methods: We extracted relevant data on drug exposure and malformation rate from the records of a prospective observational registry (Kerala Registry of Epilepsy and Pregnancy) for all completed pregnancies between 1998 and 2019. A comprehensive and uniform criterion with detailed guideline was used for assessment of malformations. We employed generalised linear model to generate adjusted incidence rate ratios (aIRR) of MCM in AED exposed group as compared to AED unexposed group, after adjustment for age and educational status of mothers' and epilepsy classification.

Results: The unadjusted MCM rate was 6.2% for all the infants included in the study (148/2328); 4.7% for the unexposed group (16/340), and 6.6% for the exposed group (132/1988). The aIRR of MCM as compared to unexposed group was similar for all monotherapies; lamotrigine (0.50; 95% CI 0.07-3.68), levetiracetam (1.16; 0.43-3.11), oxcarbazepine (1.61; 0.62-4.21) valproate (1.71, 0.93-3.19), phenytoin (1.21, 0.51-2.90), carbamazepine (0.99, 0.54-1.82), and phenobarbitone (1.20, 0.52-2.74). However, the point estimates suggest least risk with lamotrigine and highest risk with valproate. Polytherapy with high-dose valproate carried significantly higher risk of MCM as compared to the unexposed group (aIRR=4.12; 2.18-7.79, p<0.001). The aIRR of GTCS during pregnancy was 1.63 (95% CI 1.12-2.37, p = 0.011) for monotherapy with new AEDs (lamotrigine, levetiracetam or oxcarbazepine) as compared to old AEDs (phenobarbitone, phenytoin, carbamazepine, or valproate).

Conclusion: The MCM risk was significantly higher for polytherapy with high dose valproate. It did not differ substantially between different AED monotherapies although point estimate was lowest with lamotrigine. Pregnant women on new AEDs report higher likelihood of GTCS than women on old AEDs during pregnancy.