Withdrawal - Failure rate: 20-30%.
Withdrawal, also known as coitus interruptus, is when a male
withdraws his penis from the female's vagina before he ejaculates.
This is the most common form of birth control used by younger
people who are ignorant about how the human body works. One reason
why this form of contraception is not very effective is because
several thousands of sperm are often present in precum, the thin
clear liquid which oozes out of a penis during high arousal and
especially during the friction of intercourse. Another reason is
because often the man won't pull out before some ejaculate is left
in the vagina. Pulling out before ejaculation is not only
ineffective in preventing pregnancy, but it can be very frustrating
for both partners, especially the male. Ladies, never let a guy
convince you to have unprotected intercourse because he says he
will "pull out." First of all, it's not very effective, and second,
he may not pull out in time or not at all anyway.
www.sex-project.com