In an anovulatory cycle the ovary does not release an egg. The lining of the uterus still builds up under estrogen and later sheds, so you still bleed. What's missing is the rise in progesterone that normally follows ovulation. The bleeding can be regular or irregular, light or heavy, and often passes for a normal period.
Why it matters
Without egg release, pregnancy cannot occur in that cycle. Missing ovulation now and then is common and normal. Missing it often is one of the most common treatable reasons for difficulty getting pregnant. It is easy to overlook, because regular bleeding makes everything look fine.
Common causes
PCOS is the most common cause in women of reproductive age. Thyroid disorders, high prolactin, significant stress, rapid weight change, and excessive exercise can also interrupt ovulation. It is also frequent in the first years after periods begin and in the years approaching menopause.
How it is diagnosed
Three checks help confirm whether ovulation is happening:
- a progesterone blood test about a week before the expected period (a "mid-luteal" test)
- ultrasound scans that track the growing follicle
- home ovulation kits — if they never show a clear surge, you may not be ovulating
Treatment depends on the cause, and medicine to bring on ovulation is available when needed.