Vasectomies fail very rarely, with failure rates generally around 0.05% to 0.6%. Early failure, occurring when sperm remains in the ejaculate in the months immediately following the procedure, happens in about 0.3% to 0.6% of cases. Late failure, caused by the rejoining or reconnection of the vas deferens months or years later, is even less common, around 0.04% to 0.08% or approximately 1 in 2000 cases. Overall, the effectiveness of vasectomy as a permanent birth control method is about 99.85% to 99.95%.
Early failure often results from residual sperm still present post-procedure, which is why a semen test after 2-3 months is critical before relying solely on vasectomy for contraception. Late failures can happen due to reconnection of the vas deferens but are extremely rare, and ongoing regular sperm analysis after the initial confirmation is usually not necessary.
The chance of pregnancy after vasectomy is about 0.3% or 3 out of 1000 procedures. Factors such as not using backup contraception in the first few months, surgical technique, and provider experience can influence failure risk. Vasectomies performed by urologists have lower failure rates than those by non-specialists.
