Five hundred cases of amniocentesis without bloody tap.

Five hundred amniocenteses were carried out at midtrimester for prenatal diagnosis. A 22-gauge spinal needle with a stylet was used. The needle was guided by a real-time sector ultrasonograph. A transducer was placed adjacent to the puncture site and the needle tip was observed entering the amniotic cavity. By this technique, a bloody tap was avoided. There were only three (0.6%) spontaneous abortions in this group of 496 patients. Amniocentesis guided by ultrasound is a safe method for the mother and the fetus.