'Bachelor' Colton Underwood says he had a low sperm count. Here's what that means.

Colton Underwood, the former professional football player and star of The Bachelor, is opening up about his fertility journey with husband Jordan C. Brown-Underwood, including his issues with sperm count. In a recent interview with Parents, Underwood, who came out as gay in 2021, says his “ego took a hit” when he learned that his sperm count was so low he was considered “technically infertile.”

“We were going to give our sample and freeze our sperm — day one of starting our family — and I got my sperm results back, and I had four sperm,” the reality star told the parenting outlet. “Three of them were dead. One was barely moving in my sample. It was one of those things where [I was basically] considered technically infertile. I was like, ‘This sucks. This is hard.’”

Underwood says his lifestyle — including an intense fitness regimen, taking medication and enjoying activities like biking and sitting in hot tubs — contributed to his low sperm count. “There's so many different things that people don't really understand that are contributing factors to low quality and motility in sperm,” he said. “And I was basically doing everything I possibly could to kill my sperm, and I didn't even know.”

Underwood isn't alone. As sperm counts fall worldwide at an accelerating pace, it’s becoming increasingly important for men who want to start a family to understand what it means to have a low sperm count, how it contributes to infertility and what they can do about it. Ahead, experts break it all down.

What does it mean to have a low sperm count?

Sperm count is determined with a simple test called a semen analysis that looks at sperm concentration, or how many sperm there are per milliliter of fluid. There should be about 100,000,000 sperm per milliliter in a normal semen sample. “By the WHO [World Health Organization] standards, a low sperm count is considered less than 16,000,000 sperm per milliliter of ejaculate,” urologist Dr. Amin Herati, director of male infertility and men’s health at Johns Hopkins University School of Medicine, tells Yahoo Life.

In addition to the number of live sperm present, the sample is also examined for motility (how well the sperm move) and shape. Doctors can also run a DNA fragmentation test to examine the quality of the sperm.

“Sperm count is a good screening test to determine if there is a problem [and] if [the patient] should see a male reproductive urologist like me,” Dr. Marc Goldstein, urologist at Weill Cornell Medicine, tells Yahoo Life.

It’s also a good screening test for men’s overall health. “If they get a semen analysis that [shows] the numbers are completely off, they should seek an evaluation by a qualified urologist since the frequency of cancer detection is increased among men with infertility and/or abnormal semen analyses,” Herati adds.

How does low sperm count affect fertility?

According to Goldstein, an estimated 15 to 20% of couples who are trying to conceive are unable to. In a third of those cases, the infertility is due to an issue solely with the male.

Sometimes the factor is the low count itself; there aren’t enough living, mobile sperm to reach the egg. In other cases, the “impaired quality of the sperm” is due to it having an abnormal shape, poor motility or DNA damage, Goldstein adds.

“The semen parameter numbers are tricky,” cautions Herati. A patient can have a normal sperm count, “but the DNA quality of the sperm can be adversely affected by another condition, which could limit their success of having kids or succeeding with IVF [in vitro fertilization].”

Sperm with damaged DNA — which has been associated with smoking, infections, exposure to heavy metals, taking antidepressants and other factors — can lead to issues with conceiving, even with the help of assisted reproductive technology, or result in pregnancies that end in miscarriage,

“What we often see is that couples will be told, ‘Don’t worry about your abnormal semen analysis, we can correct that with IVF,’ which is a really, really bad piece of advice,” Herati says, “because there is something affecting the DNA of the sperm. IVF is really just a way of getting the sperm to egg. It doesn’t overcome the issue intrinsic to the DNA.”

What can cause low sperm count?

Goldstein says it’s important for doctors to take the time to talk to patients and listen to their medical history, to conduct a thorough physical exam and to run a blood test for testosterone and follicle-stimulating hormone levels in addition to the basic semen analysis with DNA fragmentation. All this information creates a holistic picture that helps doctors determine the cause of low sperm count or low-quality sperm.

“The various causes [of low sperm count and quality] are typically broken down into issues with production of sperm and issues with outflow of sperm,” Herati explains.

The production of sperm can be impacted by a variety of factors. Sometimes it’s related to the sperm’s DNA itself. Other causes can be environmental, such as exposure to pollutants and toxins or exposure to significant amounts of wet heat (like multiple hot showers, hot tubs, saunas or whirlpools). Various medical therapies, including testosterone therapy, chemotherapy and radiation therapy, can reduce sperm count.

There are also anatomical conditions such as abnormal veins (known as varicocele) in the scrotum or hormonal issues that physically impair the production of sperm. Lifestyle factors can also create issues. “Anything in excess can be detrimental: extremes in diet, alcohol, drug use — prescription or illegal,” Herati says. Goldstein adds that sexually transmitted infections, most notably chlamydia, are “an increasingly common cause of infertility.”

The outflow of sperm can become an issue with preexisting conditions such as diabetes and spinal and neurological conditions such as multiple sclerosis. Sometimes scar tissue in the urethra, prostate, groin area or another body part can inhibit flow.

Can sperm count be increased?

It depends. “When we see that semen parameter abnormalities are present, for every parameter that is abnormal, the likelihood that there is something underneath the surface that we can find and correct increases,” Herati says. For instance, varicocele veins, the most common physical abnormality that contributes to infertility, can be treated very effectively with microsurgery.

Most of the issues that arise from lifestyle decisions can also be corrected. This includes heavy drinking, obesity, not exercising, using saunas and wearing tight bike shorts. This was the case for Underwood, who says his sperm health improved three months after he began making lifestyle changes and returned to normal levels within six months.

Both Goldstein and Herati urge men who are struggling to conceive to see a urologist before undergoing fertility treatment with their partner, because treating male fertility usually improves IVF outcomes. “Don’t rely on vitamins and forums and other unvetted and not validated sources,” Herati says.