Is lamotrigine a significant human teratogen? Observations from the Australian Pregnancy Register

Lamotrigine (LTG) is increasingly being prescribed in pregnancy for women with epilepsy in place of valproate (VPA), because of the teratogenic risks associated with the latter. It is therefore important to know the teratogenic hazard associated with LTG, relative to VPA and to other commonly used antiepileptic drugs (AEDs). Data from the Australian Register of Antiepileptic Drugs in Pregnancy was examined to determine the incidence of teratogenicity determined 1 year from completion of pregnancy in women who took AEDs in monotherapy during pregnancy. Compared with a 3.4% malformation incidence in women who took no AEDs (N = 118), the incidences for LTG (N = 243), carbamazepine (CBZ) (N = 302) and VPA (N = 224) were, respectively, 4.9%, 5.3% and 15.2%, the latter statistically significantly greater than the risk for no AED therapy in pregnant women with epilepsy. Logistic regression analysis showed no tendency for foetal hazard to increase with increasing LTG dose in pregnancy, unlike the situation for VPA. However, seizure control in pregnancy tended to be not as good in the women taking LTG compared with those taking VPA, though the data examined were not adequate to permit definite conclusions regarding this matter. We conclude that LTG monotherapy in pregnancy is safer than valproate monotherapy from the point of view of foetal malformations, and no more hazardous in this regard than therapy with other commonly used AEDs.