Abstract
Holoprosencephaly is a complex developmental abnormality of the forebrain occurring in early embryonic life; incidence is 1: 16,000 births. This anomaly results from failure of cleavage of prosencephalon and categorized into three forms ; alobar , semilobar and lobar (from most to least severe). A spectrum of craniofacial malformations can occur which include a monoventricular cavity, fusion of the thalami and absence of the corpus callosum, falx cerebri, optic tracts and olfactory bulb. Facial defects may affect the orbits , nose and upper lips. Associations are trisomy 13 ,18 ,polyhydramnios ,renal and cardiac anomalies. I report a case of a Pakistani woman having an antenatal ultrasound examination done showing monoventricle, fused thalami, absence of septum pellucidum and falx cerebri and hypotelorism alongwith polyhydramnios. The baby born was a stillbirth and midline facial defects including hypotelorism and midline cleft lip were identified which confirmed the diagnosis of holoprosencephaly.

Key words: Holoprosencephaly, monoventricular cavity, fused thalami, hypotelorism, polyhydramnios.