Selective second-trimester termination of the anomalous fetus in twin pregnancies.

Selective termination of the affected fetus was performed during the second trimester in 17 pregnancies in which one twin was diagnosed to be anomalous. The affected twin had a chromosomal aneuploidy in 14 cases, neural tube defect in two cases, and an inborn error of metabolism in one case. With increasing operator skill and improvement in technique, a striking improvement occurred in pregnancy outcome in the last 11 patients as compared with the first six. In four of the first six cases, the entire pregnancy was lost. Among the last 11 patients, on the other hand, no pregnancy was lost. All 11 women delivered healthy, viable infants; eight delivered at term and three delivered between 31-35 weeks. Of the various techniques used, we found intracardiac injection of potassium chloride to be the most effective, but it should not be used in monochorionic twin gestations.