Emergency Contraception After Rape

Judith A. Linden, MD; Jasmine C. Mathews, MD


April 29, 2014

In This Article

Efficacy of the Available EC Options

Estimates of the efficacy of EC are difficult, because the probability of pregnancy occurring without the treatment is difficult to calculate and is often lower than calculated.[12] Key points about each option are summarized in the Table .

The copper IUD is the most effective form of EC. It is 99% effective, and can also be used as an ongoing form of birth control.[9] An additional benefit is its efficacy in women who weigh more than 195 lb, unlike the available pill-based options. However, 2 main drawbacks prevent this from being the first choice in sexual assault survivors. First, and most obvious, the instrumentation involved (and pain or discomfort) would probably not be tolerated well in most sexual assault victims. Second, there are often limited resources for timely IUD implantation. Nevertheless, the copper IUD may be a reasonable option in sexual assault victims who are subjected to repeated assault as a form of intimate partner violence.

UPA should be considered the first drug of choice in most women who present after sexual assault. UPA is effective within 120 hours of vaginal assault in women who weigh up to 194 lb.[13] Studies showed that the pregnancy rate with UPA is 42% lower than that seen among those taking LNG when given 0-72 hours after assault, and 65% lower than those taking LNG when given in the first 24 hours after unprotected sex.[14,15] Note, however, that UPA is only more effective than LNG in women with a body mass index (BMI) greater than 25 kg/m2, or approximately 165 lb; in those weighing more than 195 lb, UPA is less effective, and the copper IUD should be considered.[16]

UPA has not been adequately studied in breastfeeding women, but is detected in breast milk after ingestion. Breastfeeding women should, therefore, be advised to "pump and dump" for 36 hours after taking UPA. The drug has also not been adequately studied in those who have become pregnant after taking it. HRA Pharma, the European manufacturer of ellaOne®, has established a registry to collect data on women who become pregnant after being exposed to UPA.

Finally, because UPA is a progesterone receptor modulator, it may decrease the efficacy of hormonal birth control. Women using UPA should be advised to use a barrier from of protection until their next menstrual period.

LNG is a reasonable choice in women who present within 72 hours of assault and who weigh less than 165 lb. Early studies reported that LNG prevented 95% of pregnancies if taken within 24 hours, 85% within 25-48 hours, and 58% within 49-71 hours.[17,18] In a more recent study, LNG decreased 50% of expected pregnancies when taken within 72 hours.[19] Of note, LNG was originally given as 2 doses of 0.75 mg each, 12 hours apart.[6] However, recent studies have shown that 1.5 mg LNG given in a single dose is as effective, and is generally well tolerated.[18,20] Unlike UPA, LNG has been deemed safe for use in breastfeeding women.[15]

LNG appears to be less effective in women with a BMI over 26 kg/m2 (approximately 165 lb), so it would not be the first drug of choice in this population.[17] Also, LNG has been shown to be less effective when given 72-120 hours after assault.[20]

Although not specifically approved for EC, oral contraceptives may be a good option for women who do not have access to or who cannot afford EC. Because there are so many different formulations of oral contraceptives, individuals must carefully follow instructions for each brand to ensure that the most effective dose is used. A complete discussion of this option, along with a chart outlining the doses for each brand of oral contraceptives that could be used as EC, is available from the Office of Population Research at Princeton University.


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