Combined Oral Contraceptives (The Pill)

January 08, 2005

Average Failure Rate: 3 - 8%

The process of ovulation is directed by hormones. Estrogen and progesterone are two hormones which direct many of the processes surrounding the menstrual cycle. Artificial analogues of these have proven an efficient form of birth control. To prevent pregnancy a woman takes a pill daily which contains both of these hormones. This is the combination pill, or simply "the pill."

"After reading [about post-fertilization effects], I realized I could no longer justify prescribing the Pill. I think most women feel life begins at fertilization. When they find out about the post-fertilization effect, they're surprised and some even rethink their decision."
-Cynthia Jones-Nosacek, MD, Family Physician, Milwaukee, WI

The estrogen works by preventing an egg from being released from the ovaries most of the time. Both the estrogen and progesterone make the uterus a hostile environment for an embryo by causing a thinning of the uterine lining. As modern combination pills contain less estrogen than their predecessors, an egg will be released by the ovaries 2-10% of the time. If fertilization takes the embryo will be unable to implant in the uterus, resulting in the death of the embryo. Although some consider this risk minimal, the most reliable sources cite the interceptive effect as a major mechanism of action; in fact, large doses of this drug are used as a 'morning after pill'.

Oral contraceptives also have some uncommon but serious health risks associated with their use, especially among smokers; these include abnormal blood clotting and heart attacks, cancer, and gallbladder disease. Side effects include loss of sex drive (libido), headaches, acne, weight gain, vaginal infections, and depression.