Vasectomy failure rate

What are the chances your vasectomy will fail? Can a vasectomy fail after 5 years? 10 years?

These are important questions, and ones that anybody (man or woman) considering relying on vasectomy as their primary method of birth control should know the answer to.

Some websites say that vasectomy is no more reliable than condoms while others imply it’s totally foolproof. So what’s the truth about vasectomy failure rates, and how does it compare to other methods of birth control?

To cut to the chase, according to the Royal College of Obstetricians & Gynaecologists1 there is 1 in 2000 chance of a pregnancy resulting from vasectomy failure – 0.05%. This figure is generally accepted as being accurate, and the figure most doctors will quote when asked for a reliability figure. This figure is based on men having been given clearance after submitting samples for analysis in order to rule out early failures and recanalization (spontaneous re-joining of the vas deferens). One study4 puts the rate at 1 in 4000 (0.025%) when DNA proven paternity of post-vasectomy babies was taken into account.

So how does vasectomy compare to other methods of birth control?

  • Female sterilization is considerably less reliable than vasectomy. The RCOG1 quotes the rate at 1 in 200 (0.5%). Tubal ligation is ten times more likely to result in an unplanned pregnancy than vasectomy.
  • The pill has a failure rate of between 0.1% and 5%3.
  • The IUD rate failure rate is between less than 1% and 2%3.
  • Condoms have a typical failure rate of 12%, and a rate of 18% in adolescents3. One study4 mentions that 40% of men “forgot” to tell partners about a condom that broke or slipped during intercourse.
  • Diaphragms and caps have a failure rate of up to 20%3.
  • Female condoms have a failure rate of up to 22%3.
  • Natural Family Planning – don’t bother! Up to 25% failure rate3.

I mentioned “Early failures” above. Before we discuss this, a word on the two types of failures normally quoted in statistics. Technical failures and contraceptive failures. The figure of how likely a pregnancy is going to occur is known as the contraceptive failure rate, and the 1 in 2000 figure quoted above is a contraceptive failure rate. Contraceptive failure rates are the ones usually quoted – and what we are mostly interested in! Technical failures (in the case of vasectomy) are where the man hasn’t had clearance after a set number of ejaculations, or specified time period.

Many studies that have looked at vasectomy failure have been very short term ones. Typically they look at 20 ejaculations, or a period of 3/4 months. Any man not having been cleared after the end of the study period is classed as an “Early failure”. More accurately it could be described as not having cleared in the studies allocated time span. The fact is that all men clear at different rates, and some may take several months longer than others to clear. Studies indicate that the vast majority of men will clear eventually given time. Vasectomy is usually quoted at less than 1% technical failure rate. Remember that most men do eventually become clear, so the technical failure rate is misleading as in the vast majority of cases a technical failure does not mean a contraceptive failure. The man just keeps submitting samples until he’s proven to be clear.

I mentioned recanalization earlier. It puzzles may people as to how exactly the vas deferens can “Grow back together”. Quite simply, one of the ways it can happen is via spermatic granulomas that may form on the cut ends of the vas deferens forming a new channel enabling a limited number of sperm to flow. But surgeons can easily prevent recanalization from happening by leaving a large enough gap between the cut ends, and using a technique known as Fascial Interposition whereby the end are folded over, stitched and then buried in adjacent tissue. The vasectomy is still reversible if necessary, but can’t spontaneously rejoin. Many of the studies into recanalization were done before the advent of facial interposition, so the rate above may well be way out of date nowadays. In fact, a new study5 published in September 2006 that compares recanalization rates using different techniques indicates that where thermal cautery and fascial interposition is used, the early recanalization rate is 0%.

There are two types of recanalization – early, and late. The vast majority of cases of recanalization happen within the first few months after the vasectomy. This is one of the reasons doctors sometimes prefer samples to be submitted at the 3 month point – to see if this has happened. One factor that isn’t clear in the case of early recanalization is “has the vas rejoined, or was the operation not successful in the first place?” Early failure (including recanalization) happens in less than 1% of all cases2. As mentioned above, most early failures will clear eventually – they are only classed as failures due to the short study duration.

So what are the chances of a vasectomy rejoining after the all clear has been given? This is known as late recanalization, and is in fact very rare. It develops in only about one in 4,000 (0.025%) of vasectomies. It has been known to occur as late as 17 months after vasectomy3.

So in conclusion, once you have submitted the samples and been given the “All clear”, vasectomy is the most reliable method of contraception currently available. Like all methods of birth control, there IS a failure rate, but this risk is considerably lower than all other methods available. In fact, babies born after vasectomy failure normally make the news media. How often can that be said about babies born of condom failure, and how many people do you know that this has happened to? If it’s suitable for you is another question altogether, and one we look at in other pages of the website.


1. RCOG guidelines
2. Safety & Effectiveness of vasectomy Schwingl PJ, Guess HA. Fertil Steril. 2000 May;73(5):923-36
3. Vasectomy surgery Harvard Medical School
4. Male contraception and no-scalpel vasectomy BCMA – Rich, B.
5. Frequency and patterns of early recanalization after vasectomy. Labrecque M, Hays M, Chen-Mok M, Barone MA, Sokal D. BMC Urol. 2006 Sep 19;6(1):25

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