The volume of their semen, the sperm count, their ability to move and their shape (sperm motility and morphology) were placed under the microscope... literally! Men in their 30s, especially after 35, had fewer healthy sperm that were normally shaped and able to move successfully compared to men in their 20s. Sperm motility (the ability to move) started deteriorating once a man reached age 30 and dropped by around a percent a year after that. The study subject's sperm morphology, in other words the shape, also started changing at around the same age. For instance, the researchers found that men in their 50s had a 16 percent drop in normally-shaped sperm.
This was a Chinese study, but fertility experts from California confirmed that similar results were found in American men. It is probably safe to assume that a decline in the quality of sperm happens after 30 worldwide, although further study is certainly needed. This, I guess, puts an end to the ancient myth that men don't have a "fertility Golden Age", unlike women. The two sexes, it seems, are not all that different when it comes to fertility. Many experts say that biologically speaking, the best age to have children is before 30 for women. This study points to the idea that men are just the same! You may like to read our tips for men on how to get their partner pregnant as well!