For a man to be fertile, he must have healthy sperm. This depends on the quantity, quality and motility of sperm released in the man's semen. A healthy quantity is over 20 million sperm per milliliter of semen. Sperm of healthy quality has a normal shape, where the head of the sperm is an oval shape and the tail is long. Healthy motility means sperm can swim on their own. If you think you have unhealthy sperm, seek diagnosis from the nearest health facility.
Attribution: Straight Talk Foundation