Oral Contraception & Risk of Pregnancy

Overview

The advent of oral contraception, most commonly called the birth control pill, or just "the pill," has allowed women to take control of their reproductive choices without having to rely on their partners. Birth control pills contain estrogen and progestin; the hormone combination suppresses ovulation so that conception cannot be achieved. The birth control pill is highly effective for most women who use it, but as with other forms of contraception, there is a risk of pregnancy among users.

Correct Usage Statistics

Planned Parenthood estimates that oral contraception is 99 percent effective, with only a 1 percent risk of pregnancy when the pills are taken correctly. Correct usage means taking the pill every day, preferably at the same time.

Sporadic Usage Statistics

The risk of pregnancy rises to 8 percent when oral contraception is used sporadically. Sporadically may mean forgetting pills and doubling up the next day, or just forgetting one here and there.

Drug Interference

Using certain medications may cause the pill to be less effective than it normally would be. Antibiotics, including oral drugs to fight yeast infections, can increase the risk of pregnancy if a couple does not use a backup method of birth control, according to Planned Parenthood. Drugs used to treat HIV and seizure disorders may also pose a heightened pregnancy risk.

Dietary Supplement Use

The dietary supplement St. Johns Wort may interact negatively with birth control pills and make them less effective.

Illness

Women who suffer from an illness that causes vomiting or frequent diarrhea may have a higher risk of becoming pregnant when using oral contraception. Digestive ailments may interfere with the normal absorption of the hormones in the pill, creating a gap in protection.