An undescended testicle is a testicle that hasn’t moved down into the scrotum by the time a baby is born. During normal development, the testicles form inside the abdomen and gradually travel downward, typically completing the journey before birth. When one or both testicles stop short along that path, the condition is called cryptorchidism, and it’s one of the most common issues found in newborn boys.
How Testicles Descend Before Birth
Testicles begin forming high in the abdomen, near the kidneys, around the ninth week of pregnancy. Over the following months, they slowly migrate downward. By about 13 weeks, they’ve reached the lower abdomen near the groin. They stay in that area from roughly the fourth through seventh month, and then the final drop happens quickly: most testicles pass through the inguinal canal (the passage connecting the abdomen to the scrotum) between 24 and 28 weeks of gestation. By 32 weeks, over 98% of developing babies have both testicles in the scrotum, and by 36 weeks the process is essentially complete.
This timeline explains why premature babies are far more likely to have an undescended testicle. A baby born at 30 weeks simply hasn’t had enough time for that final descent. In many premature infants, the testicle finishes its journey on its own within the first few months of life.
Risk Factors
Premature birth and low birth weight are the strongest risk factors. Beyond that, several other factors raise the likelihood:
- Family history of undescended testicles
- Maternal diabetes before or during pregnancy
- Smoking or secondhand smoke exposure during pregnancy
- Alcohol use during pregnancy
- Pesticide exposure during pregnancy
- Other conditions in the baby, such as cerebral palsy or abdominal wall problems
In many cases, though, no clear cause is identified. The condition can affect one side (unilateral) or both sides (bilateral), with one-sided cases being more common.
How It’s Detected
Doctors check for undescended testicles during newborn physical exams by feeling the scrotum and groin area. The testicle is classified as “palpable” if a doctor can feel it somewhere along the inguinal canal, or “non-palpable” if it can’t be felt at all, meaning it may be sitting higher in the abdomen or may not have developed properly.
One important distinction doctors make is between a truly undescended testicle and a “retractile” testicle. A retractile testicle sits in the scrotum normally but occasionally pulls up into the groin due to a muscle reflex, especially when a child is cold or anxious. Retractile testicles generally don’t need treatment because they return to the scrotum on their own and function normally. A doctor can usually tell the difference during a careful physical exam.
Why Treatment Matters
The scrotum keeps the testicles slightly cooler than core body temperature, and that temperature difference is essential for healthy sperm production and normal tissue development. A testicle that stays inside the body too long faces two main risks: reduced fertility and a higher chance of testicular cancer later in life.
Fertility
The impact on fertility depends heavily on whether one or both testicles were affected. Men who had a single undescended testicle that was corrected have a paternity rate of about 89.5%, which is nearly identical to the general population rate of 94%. In contrast, men who had both testicles undescended have a paternity rate of around 62%, with 38% experiencing infertility, a six-fold increase over the general population. Even among those who do conceive, men with a history of bilateral undescended testicles wait an average of nearly 34 months to achieve pregnancy, compared to about 11 months for those with a one-sided history or no history at all.
Testicular Cancer
Men with a history of cryptorchidism face roughly 3 to 4 times the testicular cancer risk of the general population. The risk is not limited to the testicle that was undescended. In men with one-sided cryptorchidism, cancer risk is 6.3 times higher in the testicle that was undescended, but also 1.7 times higher in the one that descended normally. Timing of surgical correction matters significantly: men whose surgery was delayed past age 11 to 13, or who never had surgery, face 2 to 6 times higher cancer risk compared to those treated at a younger age.
Surgical Correction
The standard treatment is a surgery called orchiopexy, in which a surgeon moves the testicle into the scrotum and secures it in place. Current guidelines recommend this procedure between 6 and 18 months of age if the testicle hasn’t descended on its own. The surgery is typically done as an outpatient procedure, meaning the child goes home the same day.
Orchiopexy is considered safe, with a low complication rate. The most common issues are minor: swelling, bruising, or temporary discomfort. In rare cases, the testicle can move back up out of the scrotum afterward, requiring a second surgery. Overall, though, the procedure has a high success rate and is well-established.
For testicles that can’t be felt on physical exam (non-palpable cases), the surgeon typically begins with a small camera inserted through the abdomen to locate the testicle before deciding on the best approach. When the testicle is very high in the abdomen, a two-stage procedure is sometimes needed, though a single-stage approach has better outcomes when feasible, with success rates around 88% compared to 63% for two-stage procedures in certain cases.
Hormonal Therapy
Hormone injections have been tried as an alternative to surgery, with the goal of stimulating the testicle to descend on its own. In practice, the results have been disappointing. Controlled studies show success rates of only 6 to 21%, and a major analysis of the evidence concluded that hormonal treatment is no more effective than a placebo at achieving descent. The American Urological Association recommends against using hormonal therapy for this purpose. Some European guidelines suggest it may still have a role in bilateral cases for potentially supporting future fertility, but it is not considered a replacement for surgery.
Life After Surgery
For boys who had a single undescended testicle corrected early, the outlook is excellent. Fertility is nearly normal, and while testicular cancer risk remains slightly elevated compared to someone who never had the condition, the absolute risk is still low (testicular cancer itself is uncommon). Men with a history of cryptorchidism are generally advised to be familiar with testicular self-examination so they can notice any changes early.
Boys who had both testicles undescended face a more significant fertility impact even after successful surgery. For these individuals, a fertility evaluation in adulthood can help clarify their options if they’re planning to have children. Early surgical correction, ideally before 18 months of age, gives the best chance of preserving both fertility and long-term testicular health regardless of whether one or both sides were affected.