[Prenatal diagnosis of exencephaly at 10 weeks gestation, confirmed at 13 weeks gestation].

First trimester diagnosis of the exencephaly anencephaly sequence has been reported since the introduction of transvaginal sonography, the earliest being described at 10 weeks 5 days gestation. We report the discovery of exencephaly at 10 weeks gestation. The diagnosis was confirmed by repeat ultrasonography at 13 weeks.