After a microscopic vasectomy reversal, several factors come into play that determine pregnancy. The technical aspects of the procedure must succeed. The surgeon, by experience and care to assure a watertight and tension free anastamosis, hopefully will give the patient the best chance of “having an open vas tube.”
If the reversal is successful and the tube is open, then it is the patient’s testicles turn to “man up.” The longer interval between the vasectomy and the reversal the less likely the testicles have the ability to “pick up the ball” and begin to produce normal sperm that have the ability to be motile. (No pun intended.) The longer the interval, the longer it takes the testicles to produce sperm that can get the job done. This is an imponderable; as no one knows before the reversal the potential of the testicles ability to produce sperm suitable for pregnancy.
So let’s say the reversal is perfect and sperm produced by the testicles are getting through the old vasectomy site are viable, strong, and very motile. Well then, there are the normal things that hinder pregnancy that normal couples, neither of which have had any procedure, experience.
After all this and surmounting the odds of the procedure, the testicles producing good sperm, the length of time since the reversal and the things that are sometimes difficult in pregnancy in the normal situation, pregnancy occurring is much lower percentage than the presence of sperm in the post reversal ejaculate.
This is why the couple considering a vasectomy reversal, and the attendant inconvenience and expense,need to be aware of the difference between patency and getting pregnant.