PROJECT SUMMARY This renewal application builds on our successful RAPID EC (RCT Assessing Pregnancy with Intrauterine Devices for Emergency Contraception) trial, which demonstrated that the levonorgestrel (LNG) 52 mg IUD is effective for emergency contraception (EC) and noninferior to the copper T380A for EC. In the RAPID EC trial there was 1 pregnancy among 317 LNG IUD EC users, (pregnancy risk of 0.3%, 95% CI 0-1.7%). We published the study results in the New England Journal of Medicine, and within months Planned Parenthood Federation of America’s (PPFA) National Medical Committee used our data to adopt new contraceptive care guidelines. Today, over 600+ PPFA health centers in the U.S. offer the LNG 52 mg IUD to individuals with a negative pregnancy test for 2 new situations: a) EC: within 5 days of unprotected intercourse and b) non-EC same-day start at any point in the menstrual cycle regardless of recent unprotected intercourse. However, the LNG 52 mg IUD prescribing information and CDC, WHO, and ACOG clinical guidelines, which guide clinical care outside of PPFA, currently do not recommend placement in either of these 2 new situations. The current guidelines recommend that those not within the first 7 days of the menstrual cycle and report any unprotected intercourse (UPI) in the cycle must delay LNG IUD placement and return after the next menses starts. This creates an access barrier and increases the risk of undesired pregnancy. Our goal is to assess reproducibility of RAPID EC’s findings by determining the effectiveness of the LNG 52 mg IUD to prevent pregnancy for EC and same-day start in real-world settings where users select their treatment (and are not randomized to it as in the RAPID EC trial). With guidance from a Reproductive Justice expert, we will test reproducibility and generalizability in a larger, more diverse population, to assess whether practice guidelines and standards of care should be revised. To accomplish this we will enroll 1,404 participants at 8 PPFA affiliates with one of three situations where current guidelines limit access but data support low pregnancy risk. The three groups are: 1) EC regular-cycle group - LNG IUD EC users who have had UPI within 5 days and have a known last menstrual period and regular menstrual cycles (inclusion criteria from the RAPID EC trial), 2) Same-day start (not EC) group - people choosing the LNG IUD for contraception > 7 days after onset of menses without reported UPI within 5 days, 3) EC unknown- or irregular- cycle group - individuals choosing the LNG IUD for EC without a known last menstrual period or regular menstrual cycle. All groups will undergo noninferiority comparisons. Group 1 will be compared to the historical data from the LNG IUD participants in the RAPID EC trial. Group 2 and 3 will be compared to group 1. For all groups we expect one-month pregnancy rates <1%. Rigorous, reproducible, and generalizable data on LNG 52 mg IUD use for EC or same-day start from more het...