Objective: To investigate whether first trimester exposure to lamotrigine (LTG) monotherapy is specifically associated with an increased risk of orofacial clefts (OCs) relative to other malformations, in response to a signal regarding increased OC risk.

Methods: Population-based case-control study with malformed controls based on EUROCAT congenital anomaly registers. The study population covered 3.9 million births from 19 registries 1995–2005. Registrations included congenital anomaly among livebirths, stillbirths, and terminations of pregnancy following prenatal diagnosis. Cases were 5,511 nonsyndromic OC registrations, of whom 4,571 were isolated, 1,969 were cleft palate (CP), and 1,532 were isolated CP. Controls were 80,052 nonchromosomal, non-OC registrations. We compared first trimester LTG and antiepileptic drug (AED) use vs nonepileptic non-AED use, for mono and polytherapy, adjusting for maternal age. An additional exploratory analysis compared the observed and expected distribution of malformation types associated with LTG use.

Results: There were 72 LTG exposed (40 mono- and 32 polytherapy) registrations. The ORs for LTG monotherapy vs no AED use were 0.67 (95% CI 0.10–2.34) for OC relative to other malformations, 0.80 (95% CI 0.11–2.85) for isolated OC, 0.79 (95% CI 0.03–4.35) for CP, and 1.01 (95% CI 0.03–5.57) for isolated CP. ORs for any AED use vs no AED use were 1.43 (95% CI 1.03–1.93) for OC, 1.21 (95% CI 0.82–1.72) for isolated OC, 2.37 (95% CI 1.54–3.43) for CP, and 1.86 (95% CI 1.07–2.94) for isolated CP. The distribution of other nonchromosomal malformation types with LTG exposure was similar to non-AED exposed.

Conclusion: We find no evidence of a specific increased risk of isolated orofacial clefts relative to other malformations due to lamotrigine (LTG) monotherapy. Our study is not designed to assess whether there is a generalized increased risk of malformations with LTG exposure.