Researchers at Universities of Melbourne and Queensland, Australia, compared the incidence and natures of fetal malformations (FMs) recognized at birth with those recognized in the first post-natal year. Up to 25% of malformations recognized by the end of the first year had not been detected by, or soon after, birth. Within a month of delivery, 64 of the 1245 pregnancies (5.1%) and 69 of the 1268 fetuses (5.4%) had involved FMs. By the end of the post-natal year, 85 of the pregnancies (6.8%) and 90 of the fetuses (7.1%) involved FMs. Excluding cases born <1 year before time of data analysis, the rates of occurrence of FMs were 7.4% and 7.7%, respectively. The additional pregnancies involving fetal malformations recognized by 1-year post-partum represented 21 of all the 85 pregnancies with malformations (24.7%) and 21 of the 90 fetuses with malformations (23.3%). Of 13 pregnancies aborted because of malformations, 8 were exposed to AED monotherapy, as valproate in 5, lamotrigine in 2, carbamazepine in 1; in 5 exposure occurred as AED polytherapy, including VPA in 5, LTG in 2, topiramate in 1, and acetazolamide in 1. Early and late assessments of FM are complementary, but omission of an early assessment may result in biases and loss of subjects to follow-up. 
COMMENT. Previous studies of late recognition of fetal malformations (FM) have compared frequencies at birth and several years later, with similar findings (Annegers et al 1978, cited by authors). Drugs associated with FM differed between the early abnormalities and the late detected. VPA-associated malformations were detected at birth, while carbamazepine and lamotrigine were involved in those detected late. Spina bifida with hydrocephalus and cleft lip and palate were recognized at birth, while skull abnormalities were detected late. For an accurate assessment, FM rates with AED therapy during pregnancy should be checked at or soon after birth and again at 6-12 months later.