Emergency Contraception

Within 72 hours of unprotected intercourse, birth control pills can be taken in such a way as to reduce the likelihood of pregnancy occurring.

Two Ovral (not Lo-Ovral) are taken, followed 12 hours later by two more Ovral pills. No additional pills are taken. Should Ovral not be available, good alternatives include:

• Lo-Ovral (four pills initially, followed by four more, 12 hours later)
• Nordette (four pills initially, followed by four more, 12 hours later)
• Levlen (four pills initially, followed by four more, 12 hours later)
• Triphasil (four pills initially, followed by four more, 12 hours later)
• Trilevelen (four pills initially, followed by four more, 12 hours later)

If none of these pills are available, it is likely that any standard low-dose BCP (four pills initially, followed by four more, 12 hours later) will have similar effects. These other preparations have not been studied in as much depth, however, so it is certainly preferable to use one of the listed BCPs.

With the use of emergency contraception, the risk of a pregnancy occurring is reduced by about 75%. If 100 women have a single episode of unprotected intercourse during the middle two weeks of their menstrual cycle, normally about 8 of them will conceive. If they all use emergency contraception, only about 2 of them will conceive, a 75% reduction in risk of pregnancy.

The greatest experience with emergency contraception has been within the 72-hour window. Some studies find emergency contraception is most effective the sooner it is initiated within that 72 hours. Other studies find no difference in pregnancy rates. A few studies have looked at the use of emergency contraception for up to 120 hours after unprotected intercourse and find that it can still be effective in some cases, even after 72 hours.

The menstrual cycle is usually unaffected by the use of emergency contraception. Breast tenderness is variable. Significant nausea occurs in about half of women and vomiting affects in about one in 6 women. These symptoms generally disappear within a day or two and can be moderated by using any standard anti-emetic or anti-nausea drug starting an hour before the BCPs are taken. If started after the onset of symptoms, these medications are not likely to be effective.

The mechanisms by which this contraceptive effect occurs have not been established, but should a pregnancy occur despite the use of these BCPs, there is no evidence of harm to the fetus from having been exposed.

Contraindications to use of emergency contraception are essentially the same as those for use of the birth control pill in general. Previous stroke, undiagnosed uterine bleeding, heart attack, deep vein thrombophlebitis and cancer of the breast or uterus are all contraindications to sustained pill use. The extent to which they represent risks in the context of emergency contraception is not known, but should be weighed in evaluating a patient for emergency contraceptive use.