Genetic amniocentesis in twin pregnancy.

Fifty-three patients with twin gestation were seen at the University of California, Los Angeles, between January 1, 1977 and June 30, 1983 for antenatal genetic studies. The diagnosis of twins was successfully made in 52 patients using ultrasound. Forty-eight patients with viable fetuses requested sampling of both sacs. Amniotic fluid was successfully obtained from both sacs in 47 patients. There was only one spontaneous abortion six weeks after the amniocentesis. In five patients, one of the fetuses was delivered alive, whereas another was delivered as a stillborn without any apparent reason. Eleven sets were delivered prematurely at less than 36 weeks. There were two neonatal deaths, one from prematurity and one with multiple congenital anomalies. This study showed that differential amniocentesis can be used safely to obtain reliable information about each fetus in twin gestation.