Accuracy of Ultrasound in Detection of Gross Prenatal Central Nervous System Anomalies after the Eighteenth Week of Gestation

Background/ Ultrasound (US) detection of prenatal central nervous system (CNS) anatomic anomalies is very important in making decision about therapeutic termination. In the present study, the accuracy of US in detection of gross prenatal CNS anatomic anomalies has been investigated.Patients and 3012 pregnant women were scanned after 18 weeks of gestation by an expert operator in a referring center. All delivered fetuses were followed after birth through clinical examination and sonography. In this study, the accuracy of US in detection of gross CNS anatomic anomalies of fetuses after 18 weeks gestation was found to be 100%. The sensitivity, specificity, positive and negative predictive values of US were 100%. In sonographic examination of these 3012 pregnant women, 36 fetuses were detected with CNS anomalies, some of whom had more than one anomaly. Gross CNS anomalies observed included microcephaly, hydrocephaly, anencephaly, holoprosencephaly, ventriculomegaly, meningocele, encephalocele, lissencephaly, agenesis of corpus callosum, bilateral choroid plexus cysts and hypoplastic cerebellum. US is highly operator dependent and operator experience may be the most determinant affecting the results. Sonographic scanning after 18 weeks of gestation is associated with the best results.