Congenital absence of the vas deferens. The fertilizing capacity of human epididymal sperm.

Congenital absence of the vas deferens has been considered a virtually untreatable cause of male sterility. Furthermore, sperm that have not passed through at least the head of the epididymis have been thought to be incapable of causing pregnancy. We attempted to determine whether human sperm that had never passed through the epididymis could fertilize eggs in vitro and whether the technique could be used for men with congenital absence of the vas deferens. Twenty-eight men with congenital absence of the vas deferens underwent microsurgical aspiration of sperm from the epididymis and vasa efferentia for attempted in vitro fertilization of their wives' oocytes, with subsequent transfer of embryos. Thirty-two treatment cycles were begun (four were repeat cycles). The most motile sperm were found in the proximal epididymis, at or near the vasa efferentia. Embryos were obtained for transfer in 21 cases (66 percent). Ninety-three embryos resulted from 352 mature oocytes (fertilization rate, 26 percent). Clinical pregnancy was achieved in 10 of the 32 treatment cycles (31 percent). Seven women delivered normal infants, and three miscarried. One of the seven live births was of twins. There were six girls and two boys. When fewer than 10 eggs were retrieved, no pregnancy occurred. When 10 or more eggs were retrieved (20 cases), the pregnancy rate was 50 percent. Sperm from the proximal caput epididymidis and even sperm from the vasa efferentia (which have never passed through the epididymis) can fertilize the human oocyte in vitro and result in pregnancy with live birth.