Researchers have discovered what gives human sperm the strength to succeed in the race to fertilize the egg. The findings could lead to better sperm-selection methods in IVF clinics, with the fittest sperm being identified under conditions that mimic nature more closely.
The researchers, from the universities of York and Oxford, in England, discovered that a reinforcing outer-layer which coats the tails of human sperm is what gives them the strength to make the powerful rhythmic strokes needed to break through the cervical mucus barrier.
Only around 15 out of the 55 million sperm that embark on the treacherous journey to fertilize the egg are able to make it through the reproductive tract where cervical mucus, which is one hundred times thicker than water, forms part of one of nature’s toughest selective challenges.
“We still don’t fully understand how, but a sperm’s ability to swim could be associated with genetic integrity. Cervical mucus forms part of the process in the female body of ensuring only the best swimmers make it to the egg,” says Dr. Hermes Gadelha, from the Department of Mathematics at the University of York. “Our study suggests that more clinical tests and research are needed to explore the impact of this element of the natural environment when selecting sperm for IVF treatments.”