Amniography in second trimester diagnosis of myelomeningocele.

Twenty-eight fetuses, at 14-22 gestational weeks, were examined by amniography to identify a thoracic, lumbar, or sacral myelomeningocele. The end point was a fluoroscopic spot film with the fetal back in profile, to show the presence or absence of a bulging midline mass. Fetal irradiation was 0.66 rad +/- 0.36 (SD). There were 26 true negatives and one indeterminate examination. The one true positive was in a patient who had just had negative real-time ultrasonography. It is suggested amniography be used (1) when ultrasonography and amniotic fluid alpha fetoprotein determination disagree about the presence of a neural tube defect, and (2) for further confirmation when both these tests are positive.