Ascertainment of malformations in pregnancy registries: Lessons learned in the North American AED Pregnancy Registry

Background: Pregnancy registries, designed to assess the safety of medications and vaccines for the exposed mother and fetus, have been developed since the 1990s. Malformations present in the exposed liveborn or stillborn infant or fetuses in elective terminations are the outcome of greatest concern. The experiences of the North American AED (antiepileptic drug) Pregnancy Registry (NAAPR) can be used to identify the challenges and limitations of a pregnancy registry in identifying congenital malformations.

Methods: The NAAPR enrolls pregnant women who are taking one or more AEDs for any medical condition, but primarily to prevent seizures, and an unexposed comparison group. Participants are interviewed by clinical research coordinators (CRCs) at enrollment, later in pregnancy and postpartum. Malformations are identified in the mother's reports and her infant's medical records through age 12 weeks. A teratologist, blinded to exposure status, evaluates each potential malformation identified.

Results: Among 10,982 pregnancies enrolled between 1997 and 2022, 282 malformations were identified in the 9677 AED-exposed and 15 among the 1305 unexposed infants. Isolated malformations, such as cleft palate, accounted for 84% of the malformations identified. Increased frequencies of oral clefts and myelomeningocele were associated with exposure to several different AEDs. Copies of reports from many diagnostic studies were not obtained and very few pregnancy losses had autopsies.

Conclusions: The evaluation of the AED-exposed infants in a pregnancy registry is indirect. Improvements rely on the rapport established with the mothers by the CRCs and the mothers' willingness to assist in obtaining information from her infants' physicians.