RESUMEN
Ultrasound is an effective and noninvasive modality for the prenatal diagnosis of central nervous system anomalies and thus helps in deciding about therapeutic termination. To determine the frequency of central nervous system anomalies using perinatal ultrasound in a tertiary care hospital. Pakistan Institute of Medical Sciences, Islamabad, one year [June 2011 to May 2012] Eleven Thousand Five Hundred [11500] pregnant women referred by obstetricians and gynecologists for routine anomaly scan. Women with fetuses that had anatomical anomalies in non CNS structures [rest of the body] were excluded. Antenatal ultrasound was done by consultant radiologist using high resolution ultrasound unit. Out of 11, 500 pregnant women, CNS anomalies were detected in 48 cases.They included hydrocephalus in 21 [43.8%] anencephaly in 11 [22.9%], spina bifida in 8 [16%], 02 each [4.1%] with encephalocele, arachnoid cysts, hydranencephaly and 01 each with exencephaly and holoprosencephaly. Prenatal ultrasound is a reliable non invasive method for the diagnosis of central nervous system malformations