US remains the screening procedure of choice for antenatal evaluation because of its relative safety, low cost and its efficiency in early detection of fetal CNS anomalies compared to MRI which cant be done in the first trimester and most of the neural tube defect anomalies can be accurately in the first trimester. MRI examination will reversed only for cases with limited US examination as in cases of oligohydramnios, maternal obesity and small occipital encephalocele.