Anovulation

When a menstrual cycle does not release an egg. One of the three Rotterdam criteria for PMOS, and the most common reason fertility takes longer in this condition.

RN-reviewed

Anovulation is the absence of an egg release during a menstrual cycle. The cycle may still produce a bleed, sometimes regular-looking, sometimes irregular, but no follicle ruptures and no egg is released.

In PMOS, anovulation happens because the maturation of follicles inside the ovary stalls. Several small follicles develop partway and pause; none reaches full maturity. The hormonal signals that normally trigger ovulation do not assemble in the usual rhythm. Cycles become unpredictable.

Anovulation is one of the three Rotterdam criteria for PMOS diagnosis (the others are hyperandrogenism and polycystic ovary morphology on ultrasound). It is also the most common reason fertility takes longer in PMOS, since no egg released means no chance of conception that cycle.

The cycle pattern most associated with anovulation is fewer than nine periods a year, or cycles longer than 35 days. A clinician can confirm anovulation with a progesterone measurement about a week before the expected next period.

See also
GlossaryOligomenorrhoeaGlossaryRotterdam criteriaMechanismYour PMOS Cycle Isn’t 28 Days
Sources
  1. Teede HJ, Misso ML, Costello MF, et al. International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Monash University Centre for Research Excellence in PCOS. 2023.
  2. Teede HJ, Costello MF, Misso ML, et al. Polyendocrine metabolic ovarian syndrome, the new name for polycystic ovary syndrome: a multistep global consensus process. The Lancet. 2026.
Note

Reviewed by Mary Kristine Zabala, RN, EMHI before publication.

This is plain-language definition copy, not medical advice. For decisions about your care, talk to a clinician who knows your history.