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This study evaluates the relationship between menstrual cycle length and ovarian reserve biomarkers and stimulation responses during fertility treatments.

March 13, 2026Open Access

Association between menstrual cycle length and ovarian reserve markers and stimulation response: a retrospective cohort study

Key Points

This study evaluates the relationship between menstrual cycle length and ovarian reserve biomarkers and stimulation responses during fertility treatments.
Reviewed medical records of women undergoing infertility evaluations from January 2022 to April 2025.
Included 440 normo-ovulatory women grouped by menstrual cycle length (21–28 and 29–35 days).
Recorded demographic characteristics and ovarian reserve markers such as AMH and antral follicle count (AFC).
Documented controlled ovarian stimulation (COS) outcomes like retrieved oocytes and fertilization methods.
AMH and AFC levels were significantly lower in women with menstrual cycle lengths of 21–28 days than those with 29–35 days (p < 0.001 for both).
Fewer oocytes were developed and fewer metaphase II oocytes were retrieved in shorter menstrual cycle lengths (p < 0.001 for both).
Clinical pregnancy rates were significantly lower in the 21–28 days group compared to the 29–35 days group (p = 0.017).
Longer cycles correlated with higher AMH and AFC levels and greater oocyte yields after stimulation.

Abstract

To evaluate the relationship between menstrual cycle length (MCL) categories and ovarian reserve biomarkers and controlled ovarian stimulation (COS) response levels. Medical records of women undergoing infertility evaluations between January 2022 and April 2025 were reviewed. A total of 550 women undergoing fresh IVF/ICSI cycles were screened for eligibility, and 440 normo-ovulatory women who met all inclusion criteria were included. Patients were grouped according to MCL (21–28 and 29–35 days). Demographic characteristics (age, body mass index), baseline hormonal parameters (anti-Müllerian hormone (AMH), cycle day-3 follicle-stimulating hormone, luteinizing hormone, and estradiol), and antral follicle count (AFC) were recorded. COS outcomes including the number of retrieved and metaphase II (MII) oocytes, follicular output index (FOI), and follicle-to-oocyte index (FORT) were documented. Fertilization was achieved via IVF or ICSI, and embryo transfer was performed on days 2–5. AMH levels were significantly lower in the MCL (21–28 days) group than in the MCL (29–35 days) group (p < 0.001). AFC levels were significantly lower in the MCL (21–28 days) group than in the MCL (29–35 days) group (p = 0.003). The number of oocytes developed after stimulation was significantly lower in the MCL (21–28 days) group than in the MCL (29–35 days) group (p < 0.001). The number of MII oocytes was significantly lower in the MCL (21–28 days) group than in the MCL (29–35 days) group (p < 0.001). The clinical pregnancy rate was significantly lower in the MCL (21–28 days) group than in the MCL (29–35 days) group (p = 0.017). Within the normal range of MCLs, longer cycles are associated with higher AMH and AFC levels and greater oocyte yields after controlled ovarian stimulation. Although women with longer cycles showed higher crude clinical pregnancy rates, MCL was not an independent predictor of clinical pregnancy once ovarian reserve markers were accounted for. These findings suggest that MCL is a simple, history-based indicator of underlying ovarian reserve and ovarian response.

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