A vasectomy stops sperm (microscopic cells that join with eggs to cause pregnancy) from travelling through tubes in the scrotum called the vas deferens. It is an effective method of birth control.

However, a semen analysis can reveal sperm months after the operation, and it’s important to use an alternative form of birth control until this test comes back sperm-free.

Semen Analysis

A semen analysis is the first step in assessing fertility after vasectomy. It measures if the testes continue to make sperm, if those sperm are able to move (motility), and if the sperm have an abnormal shape that makes them less likely to fertilize an egg.

Patients are instructed to masturbate into a cup at home or in the doctor’s office to collect a semen sample for testing. It’s important to use only a special lubricant provided by the laboratory to ensure a clean, accurate sample for testing. Using any other type of lubricant may cause the sperm count to be inaccurate.

If the semen analysis is normal, it’s an indication that the vasectomy was a success. If the semen analysis is abnormal, it’s time to start looking into male factor infertility — which is present in about one-third of infertile couples.

A comprehensive semen analysis measures the quantity and quality of the semen fluid released during ejaculation. It also evaluates sperm movement, sperm morphology, and pH, which describes the acidity of the semen. It’s performed by an andrologist in a reproductive medicine laboratory, which is equipped to identify subtle sperm abnormalities. This is the most thorough test that can be performed, and it is best done by an experienced clinician to get the most accurate results.

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After a vasectomy, men are advised to wait 12 weeks or 20 ejaculations until their semen is free of sperm. The sperm in a man’s semen can cause pregnancy if it reaches the penis, and vasectomy prevents sperm from reaching the penis. This makes a vasectomy a very effective method of birth control. However, many men who receive vasectomies may still be able to get pregnant, even after waiting the recommended amount of time.

According to a study published in September 2003 in the Journal of Urology, men who undergo vasectomy by simple ligation and excision (in which a short segment of the vas deferens is cut, removed and tied) experience a significantly faster rate of sperm clearance than those who have their vasectomy by other methods. The study authors suggest that the shortened period of waiting for a man to achieve azoospermia reflects the rapid occlusion of the vas deferens by the ligation and excision procedure.

The results of an ejaculation performed after vasectomy are not reliable for the diagnosis of azoospermia, because a man may dribble or shoot semen in places other than his penis. It is also important to remember that ejaculating causes muscles in the pelvic and penile areas to contract, so a man may not be able to produce any semen at all.

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Testicular Growth

A surgical operation known as vasectomy is the most common method of male sterilization. It’s a safe and effective method that works as a permanent form of birth control by cutting off the tubes that carry sperm from the testicles to the penis. It does not affect a man’s ability to perform sexually or to feel pleasure. It also does not change male hormones, sex drive or semen production.

A small amount of sperm still remains in semen after vasectomy, and it takes time for these sperm to disappear. This process is called recanalization, and it may take months or in rare cases, years after vasectomy to complete. In the meantime, men must continue to use a backup method of birth control to prevent pregnancy.

Testicular growth is normal after a vasectomy, but it can cause discomfort during ejaculation or intercourse. If testicular growth causes pain, it’s a sign that the incision site is not healing properly and should be examined by a doctor.

Other complications of a vasectomy include an infection in the scrotum (or rectum) or a blood clot inside the scrotum called a haematoma. This occurs when blood collects and clots around a broken blood vessel. A hematoma is often small, but sometimes it can be large enough to fill the entire scrotum. In these cases, a physician may need to drain the scrotum or remove part of the scrotum to treat the haematoma.

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Sperm Morphology

A sperm morphology analysis is one of the many tests that can be done during a semen analysis. It looks at the shape of a sperm cell, specifically at its head (the part that carries genetic material from dad), neck and tail. The goal of a sperm morphology is to see if the cells are healthy enough to enter an egg and fertilise it.

The results of a sperm morphology can vary greatly, and some laboratories use different systems to calculate the result. However, most fertility experts agree that a normal sperm morphology score is anything above 4%.

Abnormal sperm morphology can have an effect on fertility, but there are many other factors that play into it. For example, a high number of sperm that aren’t shaped correctly could mean that the sperm won’t be able to pass through a woman’s vagina and enter her egg.

It can take time and multiple ejaculations before you’re sure you’re sterile after having a vasectomy, but the risk is far less than it would be if you were to use any other form of birth control. Until you’re certain you’re sterile, it’s important to continue using extra contraception as needed. The only way to know for sure is by testing your semen, and you’ll have the most accurate test results if you wait at least 8 weeks after your vasectomy.