Foetal malformations after exposure to antiepileptic drugs in utero assessed at birth and 12 months later: observations from the Australian pregnancy register.

Background: In studies investigating foetal malformations associated with antiepileptic drug exposure during pregnancy, the common practice has been to assess the incidence and nature of the malformations at, or soon after, birth. The adequacy of this approach to determine the true incidence of the malformations has received little attention.
Aims of the Study: To compare the incidence and natures of the foetal malformations recognized by, or soon after, birth with similar data for malformations recognized in the first post-natal year.
Methods: Analysis of data from the Australian Register of Antiepileptic Drugs in Pregnancy.
Results: Up to 25% of the malformations recognized by the end of the first post-natal year had not been detected by, or soon after, birth. There was a tendency for the late-recognized malformations to differ from the early-recognized ones in relation to the body parts involved.
Conclusions: Early assessment and delayed assessment of infants for the presence of foetal malformations are complementary, with the latter resulting in finding a higher incidence of malformations. However, omission of an early post-natal assessment may result in biases because of loss of subjects to follow-up.
(© 2010 John Wiley & Sons A/S.)