Eligible studies included a defined population of women who presented for emergency contraception and were provided with an intrauterine device. Studies had to measure the number of pregnancies and define loss to follow-up.
In the included studies, nearly all the intrauterine devices were copper bearing but some plastic devices were used in earlier studies. Most studies followed the standard protocol of inserting the device within five days of unprotected intercourse; in a few studies devices were inserted up to seven, 10 or more days after intercourse. Studies were published between 1979 and 2011 and were conducted in China, Egypt, Italy, Netherlands, USA and UK.
The authors did not state how many reviewers selected studies for the review.