Birth Control: Contraceptive Measures after Unprotected Sex

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Introduction to birth control

If a woman is sexually active and she is fertile and physically able to become pregnant, she needs to ask herself, "Do I want to become pregnant now?" If her answer is "No," she must use some method of birth control (contraception).

Terminology used to describe birth control methods includes:

Regardless of the terminology used, sexually active people can choose from a variety of methods to reduce the possibility of their becoming pregnant. No method of birth control available today offers perfect protection against sexually transmitted diseases or STDs, except abstinence.

In simple terms, all methods of birth control are based on either preventing a man's sperm from reaching and entering a woman's egg (fertilization) or preventing the fertilized egg from implanting in the woman's uterus (her womb) and starting to grow. New methods of birth control are being developed and tested all the time. What is appropriate for a couple at one point may change with time and circumstances.

Unfortunately, no birth control method, except abstinence, is considered to be 100% effective.

Emergency contraception definition

Emergency contraception is a medication or device that is used to prevent conception after unprotected intercourse has already occurred. It is not intended for use as a primary method of contraception and is most appropriate as a back-up method. Between 2006 and 2010, about 1 in 9 women of reproductive age in the US report having used emergency contraception. Emergency contraception can involve the administration of hormones or the insertion of an intrauterine device (IUD).

What is emergency hormonal contraception (morning after pill)?

Emergency hormonal contraception is sometimes called "the morning after pill" or "postcoital contraception," although these are not the preferred terms, and actually can be misleading. It is actually a short course of the hormones found in oral contraceptives taken at a high dose. The exact regimen (the number of pills and the number of days) depends on the type of oral contraceptive used.

How does the morning after pill work?

Depending upon the time during the menstrual cycle that the emergency contraceptives are taken, these may prevent pregnancy by blocking the implantation of the fertilized egg in the uterus, by inhibiting ovulation, or by interfering with fertilization of the egg.

  • To be considered a possible candidate for emergency contraceptive pills a woman should take the medication within 72 hours of unprotected intercourse, although there is some evidence that they may be effective in the 5 days following intercourse.
  • Because the pills may be taken up to 72 hours later, the term "morning-after pill" is misleading.
  • However, the pills are most effective when taken as soon as possible after unprotected intercourse.
  • The only known contraindication to emergency contraception is pregnancy, so a woman must not be pregnant when these methods are used.
  • Emergency hormonal contraception may be taken on any day of the menstrual cycle.
Medically Reviewed by a Doctor on 2/18/2015

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