How Effective Is a Vasectomy?
According to the Royal College of Obstetricians and Gynaecologists, only one out of every 2,000 vasectomies is unsuccessful. This is significantly better than the rate for female surgical sterilization, which is called tubal ligation. About one out of every 200 to 300 tubal ligations is unsuccessful.
According to the National Institutes of Health, in the first year after Vasectomy, 15 to 20 out of ten thousand couples will experience a pregnancy. In comparison, approximately 1400 couples using a condom and 500 couples using oral contraceptives will experience a pregnancy each year. So the conception rate is very low.
It’s possible (but extremely rare) for sperm to cross the void between the separated ends of the vas deferens.
The main reason that a man could impregnate a woman after undergoing a vasectomy is having unprotected sex too soon after the vasectomy procedure has taken place. Couples must adhere to the requirement that the man continue to use other birth control until the remaining sperm are cleared out of the semen. This process usually takes 3 months, and 15 to 20 ejaculations. At 3 months, 20% of men will still have sperm in their semen, and must wait longer for sperm to clear.
It is critical for a man to be tested prior to having unprotected intercourse to ensure that sperm has cleared from his semen. In order to be positive that the vasectomy was successful, Dr. Fisch’s vasectomy patients undergo semen analysis periodically after the vasectomy. Semen analysis is the only way to verify that ejaculated semen is free of sperm.