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Index to this page

Birth Control

Mechanical and/or Chemical Barriers

Male Condom

Female Condom


Cervical Cap


Hormonal Contraception

Oral Contraceptives; the "Pill"

Skin ("Transdermal") Patch

Vaginal Ring

Injectable Contraceptive

Contraceptive Implant

"Morning After" Pill

The most popular formulation in the U.S., called Plan B One-Step®, contains a high dose of a progestin. If taken within 72 hours after unprotected intercourse, the drug interferes with ovulation and, if ovulation has occurred, with fertilization.

If so many days have elapsed that implantation has occurred, RU-486 may be used.

RU-486 is a synthetic steroid related to progesterone. Unlike the progestins discussed above, that mimic the action of progesterone, RU-486 blocks the action of progesterone. (Synthetic molecules that mimic the action of a natural molecule are called agonists; those that oppose it are antagonists.)

RU-486 (also known as mifepristone) is a progesterone antagonist. It binds to the progesterone receptor, and in so doing prevents progesterone itself from occupying its receptor. Thus the gene transcription normally turned on by progesterone is blocked, and the proteins necessary to begin and maintain pregnancy are not synthesized. [More]

Because RU-486 is used after implantation, it is causing an early abortion and thus has been subjected to controversy.

Intrauterine Devices (IUD)

Natural Family Planning - Rhythm Methods


All methods of birth control have been the subject of controversy (except for natural family planning).


Roughly one-third of U.S. couples still in their reproductive years have chosen for one or the other to be sterilized.

Tubal Ligation


Quinacrine Sterilization (QS)


Popularity (% using the method) and relative effectiveness of several methods of birth control among U. S. women using contraceptives. The pregnancy rate is the number of pregnancies per 100 women in the first year of using the method.
Method Popularity Pregnancy Rate
Natural family planning (rhythm) 1% 25
Male condom 16% 17
Oral contraceptives ("the pill") 28% 0.3–8.7*
Intrauterine devices (IUD) 8.5% 0.1–1.0*
Implants, e.g., Implanon® ~1% 0.05–1.0*
DMPA injections ~3.5% 6.7
Male + Female Sterilization 37% <<1%
None   85
* The lower value is found under ideal conditions; i.e., among highly-motivated women receiving good medical care.

The bottom line: The failure rate of the pill, patch, and vaginal ring, as they are commonly used, is 20 times that in women using an IUD, or implant.

Future Prospects

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3 April 2015