The detection of spina bifida before 10 gestational weeks using two- and three-dimensional ultrasound.

We present three cases of spina bifida during the embryonic period detected by ultrasound before 10 weeks' gestational age. The last-menstrual-period-based ages ranged from 9 weeks 1 day to 9 weeks 4 days and the crown rump lengths ranged from 22 mm to 28 mm. The cases were identified prospectively in a program of targeted ultrasound examination of high-risk pregnancies, using a 7.5 MHz annular array transvaginal transducer. The use of 3D ultrasound made additional diagnostic ultrasound tomograms possible, but was not necessary for the definite diagnosis. The scalloping of the frontal bones and the Arnold Chiari malformation did not occur before 12 weeks.