Poster Abstracts

Abstract

Objectives: Progestin-only pills (POPs) prevent pregnancy through a combination of mechanisms including ovarian suppression and cervical mucus changes. In this study, we sought to evaluate the potential contraceptive efficacy of a norgestrel 75 mcg POP based on cervical mucus and ovulatory effect changes during a 28 day cycle. Methods: We recruited persons ages 18-35 with normal cycles from two US academic medical centers. Participants took norgestrel 75 mcg daily for 28 days at the same time each day (within 3 hours of previous dosing), recorded through a text message based e-diary. We evaluated participants on the day of pill initiation and then at least every 3-4 days for cervical mucus scoring using a 4-category/12-point Insler scale [score ≥9 (favoring fertility), 5-8 (intermediate), and ≤4 (unfavorable to fertility)], ultrasound assessment of follicular activity, and serum hormone levels. Results: Of the 52 participants who enrolled, 49 contributed complete data for this analysis with an overall pill compliance of 97.5%. No participants had Insler mucus scores ≥9 and 32 (65%) had scores ≤4. Based on follicular assessments and serum progesterone, 14 (35%) participants ovulated; 3 (21%) had mucus scores between 5-8 and 11 (79%) had scores ≤4. Conclusions: Norgestrel 75 mcg demonstrated consistent cervical mucus changes throughout a 28-day cycle that represent non-ideal fertility. Although ovulation occurs in about one-third of norgestrel POP users, cervical mucus changes are likely to provide the desired contraceptive effect.