MUNICH – Oral contraceptives do more than prevent unwanted pregnancy. They also make it hard to gauge a woman’s ovarian reserve, based on data from 833 women aged 19-46 years seen at a single Danish fertility clinic.
Study findings suggested that an accurate measure of a woman’s ovarian reserve can occur only after she has been off an estrogen-containing OC, probably for at least 3 months, Dr. Kathrine Birch Petersen reported at the annual meeting of the European Society of Human Reproduction and Embryology.
Mitchel L. Zoler/Frontline Medical News
Dr. Kathrine Birch Petersen
The impact of estrogen-containing OC use on reducing ovarian volume was especially pronounced in women under age 30, the reduction increased with longer durations of OC use, and the ability of OCs to mask a woman’s actual ovarian reserve was strong enough to potentially conceal a true case of premature ovarian insufficiency, said Dr. Birch Petersen, an ob.gyn. at the Fertility Assessment and Counseling Clinic at Rigshospitalet in Copenhagen.
"When we see a woman on an OC with impaired ovarian reserve, we would presume [based on these new findings] that her real ovarian reserve was about 30% higher than what we measure. We would advise her to be retested after she was off her OC for about 3 months," Dr. Birch Petersen said during a press conference before her presentation at the meeting.
The study included the first women seen at the clinic since it opened in 2011, excluding those who were pregnant or failed to supply adequate information. The cross-sectional cohort included 240 women on an estrogen-containing OC and 593 women with natural cycles.
The analysis focused on three parameters: blood level of anti-Müllerian hormone (AMH), antral follicle count (AFC), and ovarian volume. The multivariate, linear regression analysis adjusted for age, body mass index, smoking, age of maternal menopause, maternal smoking during pregnancy, preterm birth, and duration of OC use.
The analysis showed that compared with the women with natural cycles, those on an OC had a 19% relative reduction in their average blood level of AMH, a 16% relative reduction in average AFC, and a 47% relative reduction in average ovarian volume. The women on an OC also had smaller antral follicles. All three differences were statistically significant.
Seeing an effect from an estrogen-containing OC on all three measures makes sense because of their interrelatedness. The antral follicles produce AMH, and a reduction in antral follicle number as well as size would shrink the ovarian contents and result in reduced volume. These effects would not occur in women on a progestin-only OC, she said.
Dr. Birch Petersen had no disclosures.
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