The vas deferens are very small and surgically reconnecting them used to be tough. It still takes skill, but modern microsurgical techniques now make vasectomy reversal totally feasible. Between 85 and 97 percent of guys undergoing the most common type of vasectomy reversal will have sperm in their semen again.
About half of couples in which the guy has had this kind of vasectomy will achieve a pregnancy.
Of course, these are averages. The less time has elapsed since a guy’s vasectomy, the better his chances of success. The pregnancy rate is 76 percent for guys whose vasectomy was 3 years or less before their reversal, but only 30 percent for guys whose vasectomy was 15 or more years before the reversal.