How voluntary prenatal diagnosis and selective abortion increase the abnormal human gene pool

It is often assumed that prenatal diagnosis followed by the selective abortion of "defective" fetuses has a positive eugenic effect. Although mandatory selective abortion of "defective" fetuses and, more important, carriers would tend to reduce the number of deleterious genes in the gene pool, the present program of voluntary prenatal diagnosis and selective abortion actually increases the number of deleterious genes. This raises the issue of freedom of choice regarding selective abortion and societal pressure on parents to undergo prenatal testing and to abort their fetus should it have a genetic disorder or be a carrier of one.