Worn properly, condoms prevent sperm from entering the uterus.

It penetrates the egg, forms a lump on its surface, the cell wall now thickens to prevent other sperm from entering.

Fertilization changes the potential to prevent other sperm from joining the fertilized egg.

This form of immunocontraception prevents sperm from accessing an ovum.

They also thicken cervical mucus to prevent sperm from reaching the egg.

When fertilization happens, changes occur on the surface of the egg to prevent other sperm from penetrating it.

There is a problem with a woman's cervix, as from prior surgery, that prevents sperm from traveling through it.

He has shown that if he simply adds the isolated protein to eggs, it prevents sperm from binding.