Efficacy of oral levonorgestrel emergency contraception with same day etonogestrel contraceptive implant: A prospective observational study

Abstract

Objective: To determine a 1-month pregnancy rate point estimate and 95% confidence interval for guideline-supported, same-day initiation of an etonogestrel implant plus oral levonorgestrel emergency contraception.

Study design: In this single-arm, prospective observational study, all emergency contraception clients who presented to four Planned Parenthood Association of Utah clinics from February 2021 to March 2023 received information about oral levonorgestrel with same-day etonogestrel implant insertion. Participants were ≤35 years and reported unprotected intercourse within 5 days with negative pregnancy testing. The primary outcome measure was a 1-month home pregnancy test. We calculated the efficacy using a test of proportions with Yates continuity correction.

Results: A total of 160 emergency contraception clients (7.6% of 2106 approached) enrolled and 153 had 1-month pregnancy outcomes. A positive pregnancy test occurred in 2 participants resulting in an overall pregnancy rate of 1.32% (95% confidence interval 0.23%-5.19%). Ultrasound gestational dating assigned conception of the first pregnancy to 8 days before enrollment. For the second pregnancy, ultrasound dating designated conception at 5 days prior to enrollment. Limiting the efficacy rate to the single pregnancy that occurred within 5 days of unprotected intercourse, we report a pregnancy rate of 0.66% (95% confidence interval 0.03%-4.19%).

Conclusions: In this observational study of emergency contraception clients selecting oral levonorgestrel with same-day etonogestrel implant, we identified a pregnancy rate within the established range of oral emergency contraception methods alone.

Implications: Clients presenting for emergency contraception may also desire ongoing highly-effective contraception, yet current clinical guidelines serve as a barrier to same-day method initiation for the etonogestrel implant and other hormonal methods. Improving access to contraceptive method initiation will reduce the ongoing risk of unwanted pregnancy for this population.

Clinical trial registration: Clinicaltrials.gov NCT04678817; registered 12/16/20.

Keywords: Emergency contraception; Etonogestrel subcutaneous implant; Oral levonorgestrel; Pregnancy.