Hormonal, nonhormonal IUDs equally effective at preventing pregnancies

For emergency contraception, both the levonorgestrel 52 mg and copper T380A intrauterine devices (IUDs) help prevent a high proportion of expected pregnancies, according to a study.

Researchers conducted a secondary analysis involving 631 participants who sought emergency contraception, of which 312 were randomly assigned to levonorgestrel 52 mg IUD and 318 to copper T380A IUD. These participants had at least one episode of unprotected intercourse in the 5 days before study enrolment.

We report the proportion of pregnancies prevented of those expected at 1 month following IUD insertion using an established approach that assigns pregnancy risk by menstrual cycle day of intercourse. We calculated proportion of pregnancies prevented using both the day of most recent UPI and all reported UPIs within 5 days of presentation.

The number of pregnancies that should have occurred in the first month after an IUD was inserted was estimated based on the timing of unprotected sex. The result was then compared to the number of actual pregnancies that happened to determine the IUD’s effectiveness. This analysis was conducted twice, once using a single event of unprotected sex and once using all reported instances of unprotected sex.

Among levonorgestrel 52 mg IUD users, 137 (43.9 percent) reported multiple episodes of unprotected sex, and one pregnancy occurred. Among copper IUD users, 142 (44.6 percent) reported multiple episodes, and no pregnancies occurred.

In the levonorgestrel group, 14.8 pregnancies were expected using the most recent episode of unprotected sex, and 22 pregnancies were expected using all episodes within 5 days of presentation. The respective numbers of expected pregnancies in the copper group were 15 and 23.1. Levonorgestrel 52 mg IUDs prevented between 93.2 percent and 95.7 percent of expected pregnancies, while copper IUDs prevented 100 percent of expected pregnancies.