Documented Paternity Despite Azoospermia Post-vasectomy.

Vasectomy is a permanent and safe method of male contraception. One commonly used definition of success is azoospermia in one or two semen analyses after 20 ejaculates after three months. Failure is higher if less than 1.0 cm of vas deferens is removed or if a postsurgical infection occurs. There can be obvious social and legal consequences following a failed vasectomy and subsequent pregnancy. Paternity testing of the prospective father and child using automated DNA investigation employing amplified polymerase chain reaction (PCR) to compare short tandem repeat (STR) loci is accurate and readily available. A 32-year-old healthy male presented for elective sterilization after his wife delivered her third healthy full-term infant. The vasectomy was performed by ligation and excision as an outpatient. There were no intraoperative or postoperative complications. He had one semen analysis 48 days post-vasectomy that confirmed azoospermia. His wife conceived 119 days post-vasectomy, and he had two subsequent negative sperm counts. She delivered a full-term infant 385 days post-vasectomy. DNA paternity testing confirmed he was the father. Either the semen analysis was incorrect because of human error during the sperm count or small numbers of viable sperm were present despite reported preconception azoospermia. Human error is unlikely since all three tests were negative. This early failure probably does not represent recanalization but the transient release of sperm stored in the seminal vesicles or vas deferens. The time from vasectomy to laboratory-confirmed azoospermia varies. The time from vasectomy to functional azoospermia is not known, which is the reason for counseling about the risks of rare unexpected failures despite laboratory-confirmed azoospermia.