Real-time B-scan-directed amniocentesis.

Utilizing real-time B scan, 150 amniocenteses, 14 in the second trimester and 136 in the third trimester, were carried out in 143 patients. In 146 procedures, amniotic fluid was obtained with a single attempt. In four other procedures, two attempts were required, and oligohydramnios was present in two. In one, both taps were dry, while in the other a second tap yielded a slight amount of meconium fluid. One patient was tapped in a site other than that suggested by real-time scanning, and a bloody tap (Apt negative) was obtained. Clear fluid was obtained when the real-time-indicated site was used. The remaining patient had premature rupture of membranes, and two attempts yielded bloody fluid (Apt negative) and the procedure was abandoned. Amniocenteses in eight patients had failed previously (one to three attempts). With the subsequent aid of real-time B scan, fluid was obtained in a single attempt. These data suggest that real-time B scanning prior to and/or during amniocentesis is as reliable as the static B scan method and, in some cases, may have a clear advantage.