Watch how difficult it is to make a baby. As sperm travel inside a woman’s body, not only is it difficult enough to find their way through a labyrinth of dead ends, they are constantly being attacked by white blood cells. After the long journey, there may only be 20 survivors out of the original 250 million.
Sperm are foreign to a woman’s body and her body’s immune system triggers white blood cells to attack and kill them. White blood cells attack sperm from all directions and make it very difficult for the sperm to reach the woman’s egg.