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.