Updated by the Progyny Clinical Team — September 2025.
What is a varicocele?
Like a varicose vein in the legs, a varicocele occurs when blood pools within the veins in the scrotum, causing swelling and dilation. It’s a common cause of infertility as it can lead to a low sperm count, decreased motility, and reduced quality.
Doctors don’t fully understand how a varicocele affects fertility, but it is linked to higher scrotal temperature, which can harm sperm production. Testicles are located outside the body because sperm development requires a temperature about two degrees cooler than body temperature. With a varicocele, the rise in temperature can damage or kill sperm.
About 15% of people with male reproductive organs have a varicocele. Among those experiencing primary infertility, the rate increases to about 40%.
What causes it?
The exact cause of varicoceles is not fully understood. Doctors believe they develop when the one-way valves inside the veins of the spermatic cord don’t work properly. These valves normally keep blood flowing upward toward the heart. If they weaken or fail, blood can flow backward and pool in the veins. Over time, this extra pressure causes the veins to stretch and widen.
Varicoceles are more common on the left side and often appear during adolescence, a time when testicles grow quickly and need more blood flow. The added demand can make valve problems more noticeable.
How is it diagnosed?
Some people notice a varicocele on their own by feeling a mass of enlarged veins in the scrotum. Other signs may include a smaller testicle on the affected side or discomfort.
A doctor can often diagnose a varicocele during a physical exam. A scrotal ultrasound may be ordered for confirmation.
What are the treatment options?
A surgical procedure called varicocele repair can improve fertility. It is usually performed on an outpatient basis. In this procedure, a small incision is made in the lower abdomen, and the affected veins are tied off.
Other options include laparoscopic ligation, which is more common in adolescents, as well as a non-surgical procedure called percutaneous embolization.
Does it affect pregnancy outcomes?
Repairing a varicocele may improve sperm quality and increase pregnancy rates. However, study results are mixed. Outcomes may depend on semen parameters before treatment, your partner’s fertility status, and the size of the varicocele.
If sperm counts are very low and your partner is older, your doctor may recommend proceeding directly to in vitro fertilization. In many cases, this includes intracytoplasmic sperm injection, where a single sperm is injected directly into an egg.
Varicocele repair has been shown to improve semen quality for most patients and carries minimal risk. It may be a good option for couples who wish to try to conceive through intercourse or intrauterine insemination.
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Disclaimer: The information provided by Progyny is for educational purposes only and is not medical advice. Always consult a qualified healthcare provider for medical guidance.