Objective: To evaluate the prevalence of enlarged ovarian follicles among users of a 20 micrograms/d levonorgestrel-releasing intrauterine system (Mirena, Leiras Oy, Turku, Finland), of subdermal contraceptive implants releasing Nestorone (Population Council, New York, New York) and of the TCu 380A intrauterine device.
Study design: A cohort study was conducted at the Universidade Estadual de Campinas, Brazil. Three hundred women were enrolled, with 100 participants in each group. Bimanual pelvic examination and vaginal ultrasound were performed during routine gynecologic examinations in women without complaints. In women with enlarged ovarian follicles (> or = 25 mm), estradiol and progesterone levels were assessed weekly until disappearance or reduction of the ovarian image.
Results: Enlarged ovarian follicles were detected in 19%, 10% and 5% of users of the levonorgestrel system, implants and intrauterine device, respectively. Most of the enlarged ovarian images disappeared after 2 weeks of follow-up. Progesterone levels showed that the intrauterine system and TCu 380A IUD (FEI, North Tonawanda, New York) users had presumably ovulated before the first ultrasound examination in contrast to the implant users.
Conclusion: Physicians and users should be aware that findings of enlarged ovarian follicles during the use of progestin-only contraceptives are transient and that no medical interventions are necessary.