What the Menstrual Cycle Can Reveal About Fertility

Ashley Strengholt
Aug 30
3 min read

Your menstrual cycle offers surprising clues about your fertility—if you know where to look.

1. Cycle Length & Regularity

A "normal" menstrual cycle typically spans 21 to 35 days, with lengths in that range often signaling regular ovulation and hormonal balance (Southern California Center for Reproductive Medicine, 2024).

Short cycles (under 21–24 days) may indicate early or absent ovulation and can prevent sufficient uterine lining development for implantation (Parents, 2023).
Long cycles (over 35 days) frequently reflect delayed or irregular ovulation, common in conditions like PCOS or thyroid imbalances, complicating conception timing (Southern California Center for Reproductive Medicine, 2024).
Irregular or absent cycles can signal hormonal disruptions—such as PCOS, stress, significant weight fluctuations, or thyroid issues—that interfere with ovulation (Verywell Health, 2024).

2. Ovulation & the Fertile Window

Ovulation—the release of a mature egg—usually occurs mid-cycle, though timing can vary (Verywell Family, 2023).

The fertile window comprises the five days prior to ovulation plus the ovulation day itself, given sperm's 3–5 day viability and the egg's limited 12–24 hour lifespan (Positive Steps Fertility, 2023).

Trackable signs like clear, stretchy cervical mucus, LH surge detection, and slight basal body temperature rises can pinpoint ovulation (Verywell Family, 2023). However, anovulatory cycles—where the body bleeds despite no egg release—are more common than many realize. Anovulation is a leading cause of infertility and affects up to 30% of cases (Cleveland Clinic, 2023; Verywell Health, 2024).

3. Hormonal Patterns & the Luteal Phase

Following ovulation, the luteal phase—typically 10–14 days—is when progesterone supports the uterine lining for implantation (Verywell Health, 2023).

A short luteal phase (under ~10 days) can compromise the lining's readiness for embryo implantation (Parents, 2023).

Irregular flow patterns also offer clues:

Heavier bleeding may suggest fibroids, endometriosis, PCOS, or thyroid imbalances.
Lighter bleeding can reflect low estrogen levels or PCOS (Parents, 2023).

4. Physical & Secondary Signs of Ovulation

Some individuals experience mittelschmerz—a mild, one-sided abdominal pain around mid-cycle that corresponds with ovulation (StatPearls, 2023; MedlinePlus, 2023). This symptom is generally harmless (Cleveland Clinic, 2023) and may affect approximately 40% of ovulating individuals (PubMed, 2023; Verywell Health, 2006).

While it can reinforce other fertility-tracking methods, it should not be relied upon alone to predict your fertile window (AVA Women, 2016; The Bump, 2023; Women in Balance, 2025).

5. Ovarian Reserve & Age-Related Decline

Your cycle and ovulation patterns only reveal part of your fertility story. Ovarian reserve—the quantity and quality of remaining eggs—is equally vital. Egg quantity and viability decrease as women age, notably after age 35 (Progyny, 2023). Irregular cycles in the late 30s or 40s may indicate declining reserve, not just hormonal imbalance. Diagnostic tests such as AMH levels and antral follicle count provide clearer insight, though tracking cycle patterns offers valuable early cues (Progyny, 2023).

Putting It All Together

When your menstrual cycles are regular (21–35 days), with ovulation signs and a robust luteal phase, it’s a promising indicator of fertility.

In contrast, short or long cycles, irregular flow, or lack of ovulation signs may point to areas needing attention—be it lifestyle adjustments or medical evaluation. Tracking your cycle is not merely record-keeping; it’s a powerful tool for understanding your reproductive health.

Want to learn more about tracking your cycle and holistic fertility coaching? Contact me below and let's chat!

References

AVA Women. (2016, January). Is ovulation pain an accurate way to know when you ovulated? AVA.
Cleveland Clinic. (2023). Anovulation: Signs, symptoms, causes & treatment.
Cleveland Clinic. (2023). Ovulation pain (Mittelschmerz): Causes & treatment.
Parents. (2023). How your period affects your chances of getting pregnant.
Positive Steps Fertility. (2023). Menstrual cycle and fertility.
Progyny. (2023). Understanding the menstrual cycle.
PubMed (StatPearls). (2023). Mittelschmerz—ovulation pain overview.
Verywell Family. (2023). Ovulating and getting pregnant.
Verywell Health. (2023). Luteal phase of the menstrual cycle.
Verywell Health. (2006). What does mittelschmerz feel like?
Women in Balance Team. (2025, May 28). Ovulation pain and pregnancy success: What you should know.