Sperm Counts Have Dropped 50 Percent. Can She Find a Fix?

Sperm Counts Have Dropped 50 Percent. Can She Find a Fix?

By Marissa Fessenden


Because sperm counts have dropped mysteriously and she’s one of the few scientists doing something about it.

By Marissa Fessenden

When a team of researchers at the Icahn School of Medicine at Mount Sinai in New York paged through thousands of scientific studies on human fertility published from 1981-2013, they discovered something shocking: The average sperm count for men in Western countries had dropped by 50 to 60 percent, and so far, experts remain at a loss as to how to treat this potential male fertility crisis.

Part of the problem is that not many researchers study male fertility, owing to poor funding and the complexity of the issue. Sarah Martins da Silva, OB-GYN at Ninewells Hospital and a lecturer at the University of Dundee School of Medicine in Scotland, is one of the few who does.

“My vision is that I can prescribe a tablet to a guy that will enhance his fertility,” she says. Martins da Silva, 46, is currently leading a substantial research program at Ninewells on the abnormal and normal function of sperm. Her work is still in the early stages, but her team has already identified two promising drugs that appear to help sperm function better.

The global fertility industry pulls in approximately $16.7 billion a year, and about 1 in 7 couples worldwide struggle with infertility. It’s a problem, though, that has long been considered a woman’s health issue, despite the fact that in roughly 50 percent of cases, male fertility is the source of the trouble. Even so, when data shows a steep decline in sperm counts, researchers speculate that environmental factors, such as exposure to pollutants, are to blame, but they’re not sure what’s causing the decline or what to do about it. 

After testing more than 3,400 drug compounds, [Martins da Silva’s team] found two that improve sperm’s ability to swim.

Martins da Silva has a calm, studied gaze and smooth brow. She grew up 10 miles from Cambridge, England, the daughter of an engineer father and a mother engaged in charity work. Her ambition to become a doctor has roots so deep she can’t recall wishing to be anything else. “From a fairly young age, I was really interested in science and really interested in how the body works,” she says.

Good grades sent her to the University of Edinburgh for both her bachelor’s degree and doctorate of medicine, with a specialty in obstetrics and gynecology. There, she met and married a fellow medical student, Mauricio Martins da Silva.

After giving birth to their first child, she accepted a job that introduced her to the research side of reproductive biology. Switching from the clinic — where there was ample opportunity to chat and interact — to the lab’s more solitary environment required an adjustment, but the questions at hand kept Martins da Silva more than engaged.


Male infertility appealed to Martins da Silva precisely because it is understudied and poorly understood. “What really motivates me is seeing a technical problem in front of me,” she says, “and then using my scientific knowledge to solve that problem.” It’s a focus that set her apart: “Being a woman studying male fertility is rare,” says Christopher Barratt, a fellow lecturer at the University of Dundee School of Medicine, who characterizes Martins da Silva as “very personable, bright [with] a real passion for the field.”

Most recently, her work has been targeted toward figuring out how to help sperm swim better, an ability that is critical to delivering the 23 chromosomes sperm carry to the egg. A sperm cell gets its propulsive power from a long and powerful tail, and while there’s still much to be learned about how that tail functions, scientists do know that the calcium within the sperm cell is essential to a strong swim and that fluctuations in calcium levels are governed by pores in the tail called CatSper channels.

Martins da Silva’s lab developed a method by which they can test a variety of drugs on sperm and then watch for specific compounds that help the CatSper channels work better. After testing more than 3,400 drug compounds, they found two that improve sperm’s ability to swim.

Still, there’s much more research to conduct, and other compounds to test, before the dream of creating a medicine for male infertility can be realized. And when they finally reach the clinical trial phase, Martins da Silva and her team anticipate many promising drug contenders will be eliminated due to unmanageable side effects or because they’re deemed not effective enough.

The advantage of the method devised by Martins da Silva’s lab is that the team can screen so many compounds quickly. This is key in research on sperm, explains Allan Pacey, a professor at the University of Sheffield and an expert on andrology. Scientists working on male fertility face limited funding, so researchers must work fast, and efficiently. That’s why the high throughput drug discovery system that Martins da Silva helped engineer has generated buzz in the press and the research field. “The kind of science she is doing is quite cutting edge,” Pacey says. 

As she pushes ahead, Martins da Silva divides her time between the clinic and the lab. A typical day might include seeing patients in the morning, testing drug responses on donated sperm in the afternoon and data analysis in the evening. She also keeps her OB-GYN skills honed: When we spoke, the multitasking fertility specialist was coming off a tiring but rewarding night delivering babies

“Sarah is very focused on the end goal,” Pacey says, “and as a doctor, is motivated by the fact that at the end of the day it is her patients that matter.”

When she isn’t running her three sons to rugby practice or walking the family’s black Lab, Martins da Silva likes to get on her bike and rack up miles cycling through the Scottish hills. It gives her space to reflect on the questions that absorb her. 

If we could understand how sperm work, she says, “then I think it would be easy to work out why people have issues.” “I find it incredible that we can put men and women in a rocket and get them to the moon or to the space station, but we genuinely don’t understand the journey that sperm need to take to get to an egg.”