Pregnancy rates are dependent on a number of factors. First, there is generally a decline in technical success rates — due to the increasing need to perform more complex and difficult epididymal repairs — as time from vasectomy increases. More importantly, pregnancy rates also decline because sperm quality and fertility tend to deteriorate progressively with time after vasectomy, due to the effects of chronic obstruction on the epidiymal duct system. These changes often result in larger numbers of sperm which have poorer motility and decreased ability to penetrate and fertilize the egg.
Decreased fertility with increasing patient age may also play a role. Traditionally, the pregnancy rates (i.e., the percentage of couples able to achieve pregnancy) for reversal surgery in most studies has been approximately the following:
|Vasectomy Reversal Pregnancy Rates|
|Years After Vasectomy||% Pregnancies|
|1 to 5 years||60 to 70%|
|6 to 10 years||40 to 60%|
|11 to 15 years||25 to 40%|
|Over 15 years||15 to 25%|
These historical pregnancy rates are somewhat dated because of progress in surgical techniques and decision-making, however. In his nearly 40 years experience with reversal surgery, including a large number of epididymal reconstructions, Dr. Finnerty has observed several interesting trends. First, in patients undergoing successful epididymal repairs, pregnancy rates were surprisingly good — even when patients were many years out from vasectomy. Second, when the epididymis was explored in men in whom epididymal obstruction was present, sperm quality in the proximal epididymis (closest to the top, near the efferent ducts where the sperm leave the the testes) was excellent, with a high percentage of active sperm, while sperm in the mid- and distal epididymis (farther from the top of the testes) was often non-motile and of poorer quality. Third, when men without epididymal obstruction had poor-quality sperm at the vasectomy site, their surgery was usually technically successful (reasonably good sperm counts afterwards), but pregnancies were relatively rare and low sperm motility was common. These findings have also been noted by Dr. Sherman Silber, one of the pioneers in microsurgical reversal surgery. This, and susequent research on the function of the epididymis, indicate that the epididymis develops abnormal function as a result of obstruction, and in many men, epididymal repair will improve pregnancy rates, even when complete epididymal obstruction is not present, but is only partial.
The main barrier to using these findings to achieve better pregnancy rates has been the ability to perform epididymal repair with high technical success rates. The extremely delicate nature of the epididymal tubule requires extensive surgical experience in order to achieve success.For more discussion on this subject, see the information on how to determine obstruction in the epididymis.