Sperm morphology (shape) is an important marker of fertility because sperm need to be a certain shape to penetrate and fertilize an egg. Having a higher number of abnormally shaped sperm is associated with infertility. However, even those with 0% normal morphology have conceived without medical assistance. The most important factor when assessing a person's chance of conceiving is their total motile sperm count (TMSC), the number of sperm in their sample that are moving or "swimming."