Science Update: Hormonal IUD as effective as a copper IUD at emergency contraception and with less discomfort, NICHD-funded study suggests

Device may also be more effective than morning after pill at emergency contraception

Graphic representation of an intrauterine device (IUD).
Credit: Stock Image

A hormone-releasing intrauterine device (IUD) appears to be as effective at emergency contraception as a copper IUD, suggests a study funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). The hormone-releasing IUD contains levonorgestrel, a synthetic form of the reproductive hormone progesterone. Compared to the copper IUD, the levonorgestrel IUD has been shown to reduce heavy bleeding and menstrual discomfort.

In addition, study participants using the levonorgestrel IUD had a 0.3% pregnancy rate, compared to the 1.4 to 2.6% pregnancy rate for oral emergency contraceptives reported by other studies. Currently, only pill formulations have been approved as emergency contraception by the U.S. Food and Drug Administration (FDA).

The study was led by David K. Turok, M.D., of the University of Utah. It appears in the New England Journal of Medicine.


Two forms of emergency contraception have been approved by the FDA, pills containing the synthetic progesterone compound levonorgestrel and pills containing ulipristal acetate, a blocking agent that prevents progesterone from entering cells. The copper IUD has not been approved for use as an emergency contraceptive and has not been compared directly to emergency contraceptive pills for pregnancy prevention. However, previous studies have shown the copper IUD to be roughly 10 times more effective at preventing pregnancy than currently approved formulations of emergency contraceptive pills.

Previous research also has indicated that, for long-term contraception, more people select the levonorgestrel IUD than the copper IUD because of the significant reduction in bleeding and menstrual discomfort reported by levonorgestrel IUD users. A preliminary study by the current study’s authors showed that among those seeking emergency contraception and willing to accept an IUD, women using the levonorgestrel IUD and levonorgestrel emergency contraceptive pills had no pregnancies resulting from emergency contraceptive failure. The emergency contraception pregnancy rate for this group was lower than what could be expected for women using levonorgestrel pills alone.


Among the 638 women who completed the current study, 317 were assigned at random to the levonorgestrel IUD group and 321 to the copper IUD group. On average, participants reported an average of 2.1 episodes of unprotected sex in the 5 days before IUD placement. The levonorgestrel IUD group had one pregnancy and the copper IUD group did not have any pregnancies. Adverse events—such as bleeding, cramping, pain, infection, nausea, and headache—occurred in 5.2% of the levonorgestrel group and 4.9% of the copper IUD group.


Based on the study results, the authors concluded that for emergency contraception, the levonorgestrel IUD appears to be as effective as the copper IUD. The study did not compare the emergency contraceptive effectiveness of IUDs to that of emergency contraceptive pills. However, the pregnancy rate of 0.3% in their study was lower than the 1.4 to 2.6% pregnancy rate reported by studies of emergency contraceptive pills, the authors noted. They added that most studies of emergency contraceptive pills were limited to participants with only 1 episode of unprotected sex within 3-5 days of undergoing emergency contraception. However, many of the current study participants were at higher pregnancy risk, having reported multiple episodes of unprotected sex in the 5 days before IUD placement. They also noted that, unlike emergency contraception with oral ulipristal acetate, which requires a waiting period before a woman can begin contraception, IUD placement provides immediate ongoing contraception.


Turok, D.K., et al. Levonorgestrel vs. copper intrauterine devices for emergency contraception. The New England Journal of Medicine. 2021.

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