Prenatal sonographic diagnosis of holoprosencephaly.

The purpose of this series was to describe the sonographic features of fetal holoprosencephaly prenatally. The study was undertaken at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai University. A total of 12 fetuses with prenatal diagnosis of holoprosencephaly were sonographically evaluated and followed-up. The study revealed that all showed monoventricular cavity, fused thalami, no falx and cavum septum pellucidum. Eight of them were correctly diagnosed sonographically in the first two trimesters. Extrafacial anomalies were also identified in half of the fetuses and all of them had facial abnormalities. Twenty-five per cent (3 cases) had polyhydramnios and only one case had oligohydramnios. Chromosome study revealed that 70 per cent had normal chromosomes, 30 per cent were aneuploidy, trisomy 13; 2 cases and trisomy 18; 1 case. In conclusion, this series indicates that ultrasound has a high predictive value in the diagnosis of holoprosencephaly. The most valuable clue to the diagnosis is the demonstration of the single ventricle. Additionally, demonstration of facial abnormalities may add confidence to the diagnosis. Conversely, should any of these facial features be serendipitously encountered, a careful examination of the intracranial contents is recommended.