Final results from 18 years of the International Lamotrigine Pregnancy Registry.

OBJECTIVE: To monitor for a signal for major teratogenicity following in utero lamotrigine exposure.
METHODS: Health care providers reported lamotrigine exposure during pregnancy, and subsequent outcomes, on a voluntary basis. Prospective reporting early in pregnancy was encouraged. Major congenital malformations (MCMs) were classified according to the Centers for Disease Control and Prevention (CDC) criteria and were reviewed by a pediatrician on the Registry's Scientific Advisory Committee. The proportion of infants with MCMs was calculated by trimester and therapy type and descriptively compared to population-based reference estimates.
RESULTS: Over an 18-year period, 35 infants with MCMs were observed among 1,558 first-trimester monotherapy exposures: 2.2%(95% confidence interval [CI] 1.6%-3.1%). This was similar to estimates from general population-based cohorts. The observed proportion of infants with MCMs among 150 lamotrigine/valproate polytherapy exposures was 10.7% (95% CI 6.4%-17.0%) and was 2.8% (95% CI 1.5%-5.0%) among 430 infants exposed to lamotrigine polytherapy without valproate. No consistent pattern of malformation type, or malformation frequency by dose, was observed. DISCUSSION: The Registry did not detect an appreciable increase in MCM frequency following first-trimester lamotrigine monotherapy exposure. With over 1,500 first-trimester monotherapy exposures, the Registry was powered to detect major teratogenicity. The proportion of infants with MCMs following lamotrigine/valproate polytherapy exposure was high, but similar to that previously reported with valproate monotherapy. The Registry failed to observe an increased MCM frequency with increasing lamotrigine dose. Monitoring of specific malformations among lamotrigine-exposed pregnancies will continue through case-control surveillance in the European Congenital Anomalies and Twins Registers network.