Chance of Pregnancy After Vasectomy

Effectiveness After Procedure

• Sperm are created in the testicles. Combined with seminal and prostate fluid, sperm travel through tubes called the vas deferens, to be ejaculated through the penis. Vasectomy involves incisions in the scrotum to cut the vas deferens, which prevents sperm from flowing into semen, states the Ohio State University Department of Urology. This procedure does not eliminate sperm that were already in the vas deferens. Those sperm will continue to be present until ejaculation removes them. Between 15 and 20 ejaculations will need to occur before the semen is free of all sperm, states the Frederick County Department of Health. This process typically takes about three months, according to the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Rate of Failure

• Vasectomies have a rate of 11 failures per 1,000 vasectomies over a period of two years, according to the Centers of Disease Control and Prevention. Of these failures, half occurred within the first three months after the procedure -- during the time when sperm is still present in the man̵7;s system. No failures have been reported 72 weeks after the procedure. The Ohio State University Department of Urology reports that their has been pregnancy in 15 of 10,000 couples one year after a vasectomy. Many of these cases were considered failed procedures due to error or reconnection, according to Harry Fisch, clinical professor of Urology and Reproductive Medicine at the Weill Cornell Medical College/New York Presbyterian Hospital. Early failure within the first few months after the procedure is usually due to unprotected intercourse before a negative semen analysis. However, early failure could also be due to surgical error when cutting the vas deferens. Late failure usually involves reconnection of the vas deferens.

Semen Analysis

• After a vasectomy, the patient will need to undergo semen analysis to determine when the semen is free of sperm. When the sperm analysis indicates fewer than 100,000 moving sperm per milliliter, pregnancy cannot occur, according to the International Planned Parenthood Federation. This level of sperm -- referred to as ̶0;azoospermia̶1; -- can occur as early as six weeks after the surgery or as long as one year, according to Fisch. Men tend to vary slightly in the timing of achieving azoospermia, with 72 percent reaching it at three months and 85 percent reaching it at six months.

Rare Reconnections

• Infrequently, the vas deferens can reconnect spontaneously, warns the UCLA Urology Department. Clinically referred to as "recanalization," this reconnection might occur due to the aforementioned surgical error or due to a sperm granuloma -- debris that accumulates at the incision site which allows the vas deferens to grow and reconnect, states the Penn State Milton S. Hershey Medical Center. Surgeons can minimize this occurrence by leaving a greater space between the incised tube ends.