Family Planning Plus

One drop. There are hundreds of millions of sperm in a single ejaculation of an average male. It only takes one sperm to fertilize an egg.

However, pregnancy risk is also dependent on many other factors. Some of these include the number of times one has sexual intercourse (of course, the more times you have unprotected sex, the greater the chance of pregnancy) and the timing of the sex in relationship to the menstrual cycle. A woman is less likely to become pregnant if the intercourse occurred just before, during, or just after her menstrual period, and more likely to become pregnant if it occurred mid-cycle. 

In order for pregnancy to occur, a sperm must unite with an egg or ovum (fertilization), and then the fertilized egg must imbed itself into the uterine wall. Each month, a woman ovulates (releases an egg from one of her ovaries into the fallopian tube). Usually, ovulation occurs mid-cycle (about two weeks before the menstrual period). The egg only lives 12-24 hours after it leaves the ovary so there is really only a brief period of time each month when pregnancy is possible. However, it is possible for pregnancy to occur several days after sex. This is because sperm can live inside a woman’s body 3-5 days. If the woman ovulates a few days after sex and there is still live sperm inside her body, pregnancy is possible.