Withdrawal (or "pulling out") is typically used as birth control measure. It is when a guy pulls his penis out of his partner's vagina before he ejaculates, or cums, so that no semen enters her body.

This can be tough though because it means a guy has to have complete control over his body so that he pulls out completely before any semen enters her vagina or gets near the vaginal opening. Sometimes orgasm happens so quickly that a guy doesn't realize he is ejaculating until it is too late.

If he is able to pull out without releasing any semen on or near the opening of the vagina, then withdrawal is pretty effective. When used perfectly, withdrawal prevents pregnancy about 96 percent of the time. But that drops to a risky 73 percent with typical or "real world" use, because many guys don't have enough control to pull out in time, especially when they're so close to the pleasure of orgasm and ejaculation. It's better than doing nothing, but there are many methods of birth control that are much more effective.

You also need to know that pre-cum sometimes contains sperm, the reproductive cells that start a pregnancy. You can learn more about why here.

A major side effect of pulling out is the risk of spreading sexually transmitted disases. Pre-ejaculatory fluid (pre-cum), the stuff that leaks from the penis before a guy comes, can carry infections and skin-to-skin contact can transmit infections such as herpes, and HPV (genital warts). Another problem is that pulling out can make sex less pleasurable for the guy and his partner. He might be worried about controlling himself and can't relax and enjoy the experience.

Guys who have sex with guys also practice withdrawal during anal sex, but the risk of spreading sexually transmitted infections is still very high for the reasons listed above. Condoms are a much safer and wiser choice to avoid STDs and pregnancy.

For more information, click on "withdrawal."