Babies who are assigned male at birth are sometimes born without one or both testicles in their scrotum — instead, the testicle(s) remain inside the inguinal canal in the groin. While this condition can either resolve on its own or be corrected through surgery, having undescended testicle(s) as a child may still affect your fertility as an adult. We’ll examine the causes of undescended testicle(s), their impact on fertility, and how you can understand if you’ve been affected.
- Undescended testicle(s) are common in babies that are born prematurely, but can affect other children as well.
- The sooner the condition resolves or is corrected through surgery, the less it’s likely to impact future fertility.
- Having two undescended testicles at birth is much more likely to result in lower sperm counts and fertility issues as an adult than having just one undescended testicle.
- You can check whether your fertility has been affected with a semen analysis.
What is an undescended testicle?
Undescended testicle, also known as cryptorchidism, is a condition in which one or both testicles do not move down into the scrotum on their own. It’s the most frequently seen genital disorder in newborns. In general, the right testicle is more likely to be affected; in 20 to 30% of cases, both testicles are undescended.
In around 80% of cases, the undescended testicle will emerge on its own by the time children are three months old. If the testicle(s) don’t descend by six months of age, however, surgery may be needed to correct the issue and lower the risk of infertility.
Sometimes, the testicle hasn’t descended because it’s missing or not fully developed. This is known as a “vanishing” testicle and occurs in under 5% of patients with undescended testicle(s).
Note that an undescended testicle is different from a retractile testicle, though the two conditions may appear similar. Retractile testicle happens when a muscle contraction pulls an already-descended testicle back into the upper scrotum. It generally moves back on its own or can be positioned by hand and doesn’t need to be corrected with surgery, but may sometimes develop into undescended testicle(s).
Since the position of the testicles can change as children grow, it’s important for the scrotum to be examined by their pediatrician at their medical appointments.
How do undescended testicles affect future fertility?
Undescended testicles may lead to reduced fertility because of impaired testicular development or because of the increased temperature of the testicle when it’s in the body instead of the scrotum. This is an issue because heat negatively affects sperm production. Research suggests that the development of cells that will later support sperm production typically occurs in babies aged 3–9 months. This process may be impeded if the testicles haven’t descended.
A recent study of over 6,000 young men found that men who were born with undescended testicle(s) had decreased testicular function. This included 28% lower sperm concentration, reduced inhibin B to follicle-stimulating hormone (FSH) ratio, and slightly impaired function in Leydig cells (which produce testosterone).
In addition to the condition’s direct impact on fertility, people who have had undescended testicle(s) in the past have a three or four-fold increased chance of developing testicular cancer. The cancer and its treatment can result in low sperm counts and infertility.
Fertility impact of one descended testicle (unilateral)
In people with one undescended testicle, around 10% may develop infertility. Research indicates that this is approximately 33% higher than the general prevalence of male infertility in North America.
Fertility impact of two undescended testicles (bilateral)
Fertility may be even more impaired in those born with two undescended testicles. One study found paternity rates of 65.3% for men born with bilateral undescended testicles — compared to 89% for men with one undescended testicle and 93% for men with no history of undescended testicle(s) — even though the condition had been corrected years earlier.
This group also had lower sperm density and levels of inhibin B (a protein that may impact sperm production) than other men. Research has shown that they may also take around three times as long to conceive compared to those born with one undescended testicle or who never had the condition.
People with two undescended testicles who don’t receive corrective surgery until adulthood are nearly always infertile, though assisted reproduction may help with conception in some cases.
What causes undescended testicle(s)?
It’s unclear why some babies are born with undescended testicle(s). It may be caused by genetics, environmental factors, hormonal issues, and a range of health conditions in the mother, which may impact the development of the testicles.
Undescended testicles are more common in babies who are born early, affecting up to 30% of preterm infants compared to approximately 1–4% of full-term infants. This is likely because the testicles don’t fully descend into the scrotum until 25–30 weeks of gestation, which may not be reached in preterm births.
Low birth weight is also a factor. Babies weighing less than 2 pounds have an almost 100% risk of undescended testicle(s).
Other potential risk factors include:
- drinking alcohol during pregnancy
- smoking cigarettes before or during pregnancy
- the mother being exposed to DES (diethylstilbestrol), a synthetic type of estrogen that may cause endocrine disruption and affect hormones
- pesticide exposure
- the mother having obesity or diabetes
- being born through cesarean section
- being born after in vitro fertilization
Retractile testicle(s) may become undescended testicle(s) in around 30% of cases, with an increased risk in those age 7 and younger.
What is the treatment for undescended testicles?
A surgery called orchiopexy is the standard treatment for undescended testicle(s). Hormone therapy has sometimes been used to cause the testicles to descend, but the American Urological Association advises against this treatment due to low success rates and limited research into its long-term effectiveness.
During the surgery, the scrotum or groin will be cut, and the testicle will be pulled into the scrotum then typically secured with stitches. The operation is likely to have better results if it takes place between the ages of 6 and 18 months, or as soon as it’s diagnosed.
Early treatment of undescended testicle can preserve later fertility
A small study examined the timing of surgery on later fertility. It found that young men who had received an orchiopexy — surgery to correct undescended testicle(s) — during their first year of life had higher total sperm counts and increased sperm motility compared to those who had the procedure between age 1 and 2.
Delays in correcting undescended testicle(s) may result in an increased loss of fertility along with a higher chance of testicular cancer.
How can I understand if my fertility has been affected?
If you were born with one or two undescended testicles or developed the condition as a child, you may wish to know whether the condition has impacted your fertility.
An at-home semen analysis can help you understand your sperm count and overall sperm health so you have more information when planning for the future.