The number and timing of unprotected intercourse sessions in the previous 14 days were used to estimate pregnancy risk following IUD insertion. This was a secondary analysis of a randomised study that compared emergency contraception with the copper T380A IUD with the levonorgestrel 52-mg intrauterine device. Participants had a negative urine pregnancy test result at the time of enrolment. Researchers looked at pregnancies one month following IUD insertion and compared pregnancy risk based on single or many unprotected intercourse events, as well as timing. One pregnancy occurred among the 655 participants, in a patient who reported intercourse once 48 hours before IUD implantation. 286 individuals reported several unprotected intercourse sessions, and 95 participants reported at least one unprotected intercourse episode 6 or more days before IUD implantation. There were no pregnancies among those who had many unprotected intercourse sessions or any unprotected intercourse episode 6–14 days prior to IUD insertion. The pregnancy risk difference did not differ substantially by single versus many unprotected intercourse sessions, nor by unprotected intercourse 5 or less days before IUD installation versus 6 or more days before IUD placement.

With a negative urine pregnancy test result at IUD insertion, the chance of pregnancy at one month remains low, regardless of the frequency or timing of unprotected intercourse in the previous 14 days.