Prenatal diagnosis of alobar holoprosencephaly by two-dimensional and three-dimensional ultrasound.

The aim of this study is to evaluate the sonographic characteristics of alobar holoprosencephaly (AH) in utero. Seventeen cases were diagnosed at 16-30 weeks' gestation by two-dimensional and three-dimensional ultrasound from October 1994 to December 1998. In this series, the prenatal prevalence was 1 out of 415 and the detection rate of AH by prenatal ultrasound was 100%. Eleven cases (64.7%) had concurrent facial anomalies. Cleft lip and hypotelorism were the most common associated facial anomalies (72.7%). Two cases (11.8%) were twin pregnancy with one fetus affected. We present one of the largest series in the literature and compare it with previous reports. From this series, we concluded that: (1) intracranial findings, including monoventricle, fused thalami, and the absence of midline structures, were reliable sonographic characteristics for prenatal diagnosis; (2) cleft lip and hypotelorism seemed to be more common associated facial malformations than cyclopia or cebocephaly with AH; and (3) although three-dimensional ultrasound did not change the diagnosis of AH made by two-dimensional ultrasound in this series, three-dimensional ultrasound does assist in defining the severity and extent of AH.