How much sperm can cause you to become pregnant?
It only takes one sperm cell uniting with an egg
to cause pregnancy. A healthy male releases about 500,000,000 sperm
with each ejaculation. While only one is needed, the large number
increases the odds that at least one will reach the egg. It should
also be kept in mind that sperm can live over six days inside a woman's
body, so even if sex does not take place on the day your egg is released,
you still can become pregnant from leftover sperm.