Selective Termination of One Twin 'Reasonable'.

VAIL, COLO. -- Even monozygotic, monochorionic twin fetuses can be discordant for a major anomaly.

And when one fetus in a multiple gestation has an anomaly, it's important that the woman be made aware that selective termination of the affected fetus is a very reasonable option, said Dr. Richard L. Berkowitz, professor and chairman of ob.gyn. at Mount Sinai School of Medicine, New York.

In the first 100 women who underwent selective termination for this indication at Mount Sinai, the loss rate of the unaffected fetus was 3%. Most losses occurred 3-4 weeks after the procedure. The other 97% delivered at a mean gestational age of 36.5 weeks. Eighty-six percent delivered after 34 weeks, he said at a conference on obstetrics and gynecology sponsored by the University of Colorado.

"I think that this experience suggests a woman in this situation really does have a reasonable option, that there is something we can do. If we do it, the potential for losing the whole pregnancy is really not a lot higher than that of a woman who enters the second trimester with a set of viable twins. It's known that the miscarriage rate for women with viable twins at 12-13 weeks is 2%-3%. So the overall loss rate of 3% with selective termination is not too bad, and the gestational age at delivery is pretty good," Dr. Berkowitz said.

Most of the cases in the Mt. Sinai series involved a fetal twin or triplet with Down syndrome. Neural tube defects were another common indication for selective termination. There were a few aneuploidies as well.

"Anything that a singleton can get, a twin can get. Sooner or later we'll find on these lists everything that a singleton can get," he said.

Most cases of fetal discordance for an anomaly that make their ...