Sperm quality appears to be declining around the world but is a little discussed cause of infertility. Now scientists are narrowing in on what might be behind the problem.

“We can sort you out. No problem. We can help you,” the doctor told Jennifer Hannington. Then he turned to her husband, Ciaran, and said: “But there’s not much we can do for you.”

The couple, who live in Yorkshire, England, had been trying for a baby for two years. They knew it could be difficult for them to conceive as Jennifer has polycystic ovarian syndrome, a condition that can affect fertility. What they had not expected was that there were problems on Ciaran’s side, too. Tests revealed issues including a low sperm count and low motility (movement) of sperm. Worse, these issues were thought to be harder to treat than Jennifer’s – perhaps even impossible.

Hannington still remembers his reaction: “Shock. Grief. I was in complete denial. I thought the doctors had got it wrong.” He had always known he wanted to be a dad. […]