How reliable is a vasectomy? And why is the semen analysis after 12 weeks so important?

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A vasectomy is one of the most reliable forms of contraception available: after a confirmed, negative sperm test, the method is more than 99% effective. However, one thing is often misunderstood: you are not immediately infertile after the procedure. Only when a laboratory has confirmed that there are no longer any sperm cells in your semen can you rely on the method. In this article, you will read exactly how reliable a vasectomy is, why the sperm test takes place after approximately 12 weeks, and how that test works.

In short: a vasectomy is >99% effective, but only after a negative sperm test. Continue using contraceptives until those results are in.

How effective is a vasectomy?

Once a negative sperm test confirms that there are no longer any (motile) sperm cells, a vasectomy is more than 99% effective — more reliable than the hormonal pill, the IUD, or condoms. This makes it one of the most certain and permanent forms of contraception.

The chance that a vasectomy "fails" after a confirmed, successful test is very small. In rare cases, the vas deferens can naturally repair itself (recanalization); this occurs in about 1 in 2,000 men. The sperm test is specifically designed to provide certainty before you stop using other forms of contraception.

Are you immediately infertile after a vasectomy?

No. This is the most important thing to remember. During a vasectomy, the vas deferens are sealed, but there are still sperm cells present in the section of the vas deferens beyond the blockage at that moment. These must first be "cleared out."

This requires time and a number of ejaculations. Until your sperm test shows a negative result, you are still fertile and must continue using contraceptives.

What is a semen analysis (sperm test)?

A semen analysis — also known as a sperm test or sperm count — is a laboratory examination where a sample of your semen is examined under a microscope. The lab checks whether any sperm cells are still present and, if so, whether they are still motile.

Why does the sperm test take place after approximately 12 weeks?

After the procedure, it takes several weeks and multiple ejaculations to clear all remaining sperm cells from the vas deferens. Performing a test too early would therefore provide an unreliable result.

The guideline is to have a test after approximately 12 weeks and after a sufficient number of ejaculations (in practice, about 20 to 30). This combination of time and ejaculations ensures that the result provides a reliable picture of your situation.

How does the sperm test work?

The test is simple and painless. You provide a semen sample to an affiliated laboratory, where it is examined under a microscope.

At De Herenkliniek, we guide you through every step so you never have to figure things out on your own:

• About a week after the procedure you will receive an email from us with instructions on how to schedule your semen analysis.
• We will then send you a reminder after 12 weeks and again after 16 weeks.
• You drop off the sample at the laboratory. The laboratory then sends the results to us.
• We review the results and inform you personally of the outcome: if the result is negative, the vasectomy was successful.

This way, you don't have to worry about a thing and can be sure that your results are being reviewed by our own specialists.

Where can you have the sperm test done?

De Herenkliniek works with leading laboratories near our locations. You can have your sperm test performed at:

• Saltro (Unilabs) in Utrecht
• Franciscus Gasthuis & Vlietland in Rotterdam
• Atalmedial (Unilabs) in Amsterdam and Amstelveen
• Diagnost IQ in Zaandam

This ensures there is always a reliable laboratory near you. Laboratory testing is not included in the €499 procedure fee; these costs vary by laboratory.

What do the results mean — and when can I stop using other forms of contraception?

A result is considered negative when there are no sperm cells left, or when the concentration is lower than 100,000 sperm cells per mL with no moving (motile) sperm cells. In both cases, the vasectomy has been successful, and you can stop using other forms of contraception from that moment on.

If the results still show (moving) sperm cells, there is no need for concern: sometimes it simply takes a little longer or requires more ejaculations. In that case, we recommend a follow-up test, and you should continue using contraception until then. Never stop using other forms of contraception before you have received a confirmed negative result.

How small is the chance that a vasectomy might still fail?

After a confirmed negative test, the chance of pregnancy is extremely low. In exceptional cases, the severed vas deferens can naturally reconnect (recanalization). This is rare and occurs in approximately 1 in 2,000 men.

That is precisely why the sperm test is so valuable: it gives you the certainty that the procedure was completely successful at that time.

Why choose De Herenkliniek?

Male sterilization is our sole focus — and you will notice that in every detail, right down to a carefully arranged sperm test at a laboratory near you. You do not need a referral , there is no waiting list and you will generally be seen within 14 days at one of our locations in Amsterdam, Rotterdam, or Hilversum. The procedure costs €499, including consultation, intake, surgery, and aftercare (excluding laboratory testing).

Schedule your vasectomy →

Frequently asked questions

Am I immediately infertile after a vasectomy?
No. There are still sperm cells in the vas deferens. You are only considered infertile after a negative sperm test — which takes about 12 weeks and a sufficient number of ejaculations.

How reliable is a vasectomy?
After a confirmed negative sperm test, a vasectomy is more than 99% reliable. This makes it more reliable than the pill, the IUD, or condoms.

When should I have the sperm test done?
Approximately 12 weeks after the procedure and after a sufficient number of ejaculations (about 20 to 30). This combination ensures a reliable result.

How do I schedule my sperm test and receive the results?
About a week after the procedure, you will receive an email from us with instructions on how to schedule the sperm analysis. We will then send you a reminder after 12 weeks and, if necessary, after 16 weeks. The laboratory sends the results to us; we review them and inform you personally of the outcome.

Where can I have the sperm test done?
De Herenkliniek works in partnership with Saltro (Unilabs) in Utrecht, Franciscus Gasthuis & Vlietland in Rotterdam, Atalmedial (Unilabs) in Amsterdam and Amstelveen, and Diagnost IQ in Zaandam.

When can I stop using other forms of contraception?
Only once you have received a confirmed negative result. Until then, you must continue to use contraception.

Can a vasectomy still fail?
Very rarely. In about 1 in 2,000 cases, the vas deferens heals naturally (recanalization). The semen analysis provides certainty before you stop using other forms of contraception.

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