Only two forms of “morning-after” contraception are approved by the Food and Drug Administration, both hormonal drugs taken orally as pills: levonorgestrel (Plan B One-Step and other brands, available over the counter) and ulipristal acetate (Ella, available by prescription). Observational studies strongly suggest that a nonhormonal copper intrauterine device (ParaGard) may also be effective.
Now researchers have found that another type of IUD, one containing the hormone levonorgestrel (Liletta and other brands) works as well as the copper IUD, and perhaps even better than the F.D.A.-approved oral pills for preventing pregnancy.
The study, in the New England Journal of Medicine, tested the copper IUD against intrauterine levonorgestrel in a randomized trial. Researchers recruited 638 women seeking emergency contraception at three Utah family planning clinics, randomly assigning them to one device or the other.
After one month, there were no pregnancies among women who used the copper IUD, and one among those who used the hormonal IUD. The researchers calculate that the incidence of pregnancy with intrauterine levonorgestrel is 0.3 percent, compared with 1.4 to 2.6 percent with oral contraceptives.
Neither of the intrauterine devices is now approved for emergency contraception, but the lead author of the study, Dr. David K. Turok, an associate professor of obstetrics and gynecology at the University of Utah, expects professional guidelines to include them soon.
“The main thing is that this is another option that may be highly attractive,” he said. “Now we have a well-designed and executed study that shows it can be used.”