Teratozoospermia causes male infertility due to a sperm factor. In the first place, sperm that are out of proportion or strangely shaped cannot travel properly, making it more difficult for them to reach the egg in the woman’s fallopian tube.
On the other hand, once they have reached the egg, at least one sperm must be able to penetrate it for fertilization to take place. Abnormalities in the head of sperm can make this action difficult.
Finally, sperm with teratozoospermia may be capable of giving rise to a pregnancy, but then the woman will suffer repeated miscarriages due to genetic alterations that are associated with some abnormal sperm.