Is lamotrigine a teratogen?

To assess whether lamotrigine (Lamictal), when used in antiseizure medication (ASM) monotherapy, is a teratogen.

Analysis of data from 490 LTG monotherapy treated pregnancies and 214 pregnancies in women with epilepsy not exposed to any antiseizure medications during at least the first half of pregnancy.

The LTG-treated and the untreated pregnancies were well matched in nearly all regards apart from ASM exposure. There was a foetal malformation (FM) occurrence rate of 4.49 % in the LTG-exposed pregnancies and 3.27 % in the untreated pregnancies (Risk Ratio = 1.37; 95 % C.I. 0.60, 3.16). Logistic regression produced no evidence that the extent of the LTG-associated malformation occurrence hazard was LTG dose related. However, the malformation-affected body regions tended to differ between the LTG-treated and untreated pregnancies.

The above findings do not reach a statistically significant level (P < 0.05) but, taken overall, they do not necessarily exclude the possibility that LTG may be a weak teratogen. If LTG monotherapy-associated foetal malformation occurrence rates are used as the comparator against which to evaluate the foetal malformation hazards associated with other ASMs, the findings may possibly be open to the risk of falsely reassuring outcomes.