A potential pitfall in the ultrasonographic diagnosis of fetal encephalocele.

Abnormalities of the fetal neural axis may be diagnosed prenatally utilizing ultrasonography. Attempts to increase the sensitivity of ultrasonography in the detection of these anomalies run the risk of increasing the false-positive diagnoses. Since the prenatal diagnosis of neural tube defects significantly affects the clinical management of the pregnancy, a false-positive diagnosis of neural tube anomaly must be avoided. The authors describe several cases of patients with polyhydramnios in which the fetal ear protruded into the amniotic fluid, simulating the appearance of an encephalocele on ultrasonography.