Actually it isn't. <span class="spoiler">The female orgasm causes the muscles along the walls of the vagina to contract, theoretically delivering your sperm to the uterus in seconds rather than hours. Sperm has to survive long enough within the female reproductive system until the egg is released into the fallopian tube, and the female reproductive system by design is a harsh place. Millions of sperm die really, really fast so the more to reach the uterus and ultimately the fallopian tubes, the better. 