Emergency contraception, or post coital contraception, refers to birth control methods used after relations have already taken place. Emergency contraception is meant for emergencies – either when a routine method has failed (e.g., a diaphragm was found to have a hole in it), or in cases of sexual assault. Emergency contraception reduces the risk of pregnancy from about 8% to about 2%.
Most rabbis permit use of emergency contraception after a case of sexual assault. Questions about emergency contraception should be asked quickly, since this method is most effective when used within 72 hours of relations.
The most commonly used method is high doses of oral hormones ("the morning after pill"). There are two formulations, either progestin alone (levonorgestrel, "Plan B"), or combined estrogen and progestin. The progestin-only method is more effective and is less likely to cause nausea.
Hormonal treatment should be initiated as soon as possible – ideally within 72 hours, and no later than 120 hours, after relations. Progestin-only pills can be administered in one large dose, or in two doses 12–24 hours apart. Combined hormones are administered in two doses taken twelve hours apart.
The pills work by disrupting the menstrual cycle. Depending when in the cycle they are taken, they may prevent ovulation, fertilization, or implantation. These mechanisms have different halachic implications: preventing ovulation is the least problematic, preventing implantation of a fertilized embryo is the most problematic. In practice, emergency contraception is generally required in extenuating circumstances and will be permitted in most such cases.
Side effects of hormonal emergency contraception can include nausea and vomiting, abdominal pain and cramps, breast tenderness, headaches, dizziness or fatigue. A woman who vomits within two hours of taking either dose may need to repeat that dose; a physician should be consulted. Generally these symptoms will go away within a few days. Menses may not occur at the expected time and irregular bleeding or spotting may occur during the week or month after the treatment. Therefore, it is advisable to be especially careful about colored underwear during this month to prevent becoming niddah unnecessarily.
Depending on one's location, hormonal emergency contraception may or may not require a prescription. In many jurisdictions, it can be bought over-the-counter by those 18 years or older by asking the pharmacist.
For women who are unable or unwilling to take hormones, or who need a longer-acting form of birth control, the intrauterine device (IUD) can also be used for emergency contraception. The IUD must be inserted by a doctor. It works best if inserted within five days after relations. The IUD prevents the fertilized egg from implanting in the wall of the uterus. Some authorities consider this mechanism halachically problematic because it resembles abortion. However, many authorities permit it – especially in extenuating circumstances – as the fertilized egg is much less than 40 days old.
While emergency contraception can greatly reduce the risk of getting pregnant, there is still a chance that pregnancy could occur. Emergency contraception does not harm a pregnancy or the health of the baby. If menses do not begin within a week of when they are expected, one should do a pregnancy test. If the result is positive, especially with an IUD in place, a physician should be consulted. Lower abdominal pain or bleeding or spotting that lasts longer than a week are also reasons to see a doctor, as these can be signs of a miscarriage or ectopic pregnancy.
Emergency contraceptive pills will not prevent pregnancy from future episodes of relations. Therefore, an additional method of birth control such as spermicide should be used until the next period. A woman who was using hormonal contraceptives before should continue to take them.