I had a vasectomy reversal last year. The first sperm test after the procedure was positive, but the second sperm test was negative. How could this be? Will my wife and I be able to have a baby?

Answers from Todd B. Nippoldt, M.D.

After a vasectomy reversal, it's possible — although somewhat rare — to have a positive sperm analysis followed by a negative sperm analysis.

There may be several possible explanations for your conflicting test results. Sometimes, lifestyle factors — including testicular temperature, smoking or the use of certain medications — temporarily decrease sperm count.

In other cases, scarring from a vasectomy reversal blocks the vas deferens — the tube that carries the sperm. When this type of scarring occurs, it usually happens soon after a vasectomy reversal — leaving a man with only negative sperm analyses. If the scarring happens later, however, a positive sperm analysis may be followed by a negative sperm analysis.

And for some men, it's simply a matter of waiting. It can take up to 15 months for sperm to appear after a successful vasectomy reversal.

To find out what's happening in your case, consult your doctor. He or she may recommend another semen analysis or perhaps a vasogram — a special X-ray used to check for blockages in the vas deferens. If a blockage is detected, it may be helpful to repeat the vasectomy reversal procedure.

If the vasectomy reversal isn't successful, you may have other options for conception. For example, it may be possible to retrieve sperm with a needle or simple surgical procedure for use with in vitro fertilization or other infertility treatments.

Sep. 10, 2008 See more Expert Answers