Sonographic markers of exencephaly at 9 + 3 weeks of gestation.

Following the introduction of transvaginal sonography, several first trimester diagnoses of the exencephaly anencephaly sequence have been reported, with the earliest being described at 10 weeks of gestation. We report a case with a high index of suspicion for exencephaly at 9 weeks and 3 days because of three sonographic features: the cranial pole of the embryo was smaller than the chest, the cranial pole bulged dorsally and the surface of the cranium was irregular. The diagnosis was confirmed by a repeat ultrasound examination at 11 + 4 weeks and by autopsy after termination of pregnancy.