Males with specific genetic defects affecting sperm morphology may be incapable of natural conception but can potentially achieve fertilization through in-vitro fertilization.

“if it's not oval enough and it's too rounded, that could be a genetic defect under which conditions there is zero probability of the male ever naturally conceiving, regardless of who the female partner is. Believe it or not, males can have a ton of sperm, but if they carry a certain genetic defect, those sperm will be incapable of depositing those 23 chromosomes into the egg. However, there are ways in which that sperm can be coaxed or forced to fertilize the egg and deposit its genetic contents by in-vitro fertilization and then implantation into the female.”