Genetic amniocentesis in twin gestations.

Among 1,613 women studied with routine ultrasonography prior to genetic amniocentesis at Northwestern University Medical School, 25 of 26 multiple gestations were detected. Sampling of fluid from both amniotic sacs was requested by 20 women with twin gestations in which both fetuses were ultrasonographically determined to be viable and of normal size. Fluid was obtained successfully from both amniotic sacs in 19 of 20 cases. The conclusions are that (1) twin gestations can be reliably detected by the use of routine ultrasonography, (2) both amniotic sacs can usually be sampled, and (3) the complication rate appears to be minimal to the patient and the fetuses, although the sample size is still small.