Sperm attacked by woman's immune system | Inside the Human Body - BBC

Survival rate00:00:55

Out of an original 250 million sperm, only as few as 20 may survive to reach the safety of a fallopian tube.

Sperm as unwanted invaders00:00:03

Sperm are considered foreign to a woman's body and are treated as unwanted invaders, triggering her immune system.

Immune system ambush00:00:13

Once sperm enter the cervix, they face a labyrinth of dead ends, perfect for an ambush by white blood cells that attack from all directions.