Conditions · FAQ
Why does polycystic ovary syndrome (PCOS) cause irregular periods?
Short answer
PCOS can prevent regular ovulation, which can make periods late, unpredictable, or absent. Going a long time without a period may allow the uterine lining to become too thick. If you have gone about three months without a period, contact a physician and take a pregnancy test if pregnancy is possible.
During a typical cycle, hormone changes help an egg mature and leave the ovary. After ovulation, the body makes progesterone. This hormone helps control the uterine lining before it sheds during a period. With PCOS, ovulation may happen less often, so this pattern becomes irregular.
When periods are very far apart, the uterine lining may stay exposed to estrogen without enough progesterone. Over time, this can raise the risk of abnormal thickening of the lining. Missing periods should not be ignored, even if you are not trying to get pregnant.
A physician may suggest hormonal birth control or planned courses of a progestin to manage bleeding and protect the lining. Results vary. The right option depends on your medical history, pregnancy plans, and other symptoms. Do not start hormones or change their schedule without medical guidance.
If pregnancy is possible, take a pregnancy test when a period is late. PCOS does not prevent pregnancy. Seek urgent care for very heavy bleeding with dizziness, fainting, shortness of breath, or severe pelvic pain.
Sources
Written by the Verra clinical team · Medical review pending
General information, not medical advice. If you're in crisis, call or text 988.
Related guides
Related questions
- What is polycystic ovary syndrome (PCOS), and what symptoms can it cause?
- How is polycystic ovary syndrome (PCOS) diagnosed?
- How can birth control help with polycystic ovary syndrome (PCOS)?
- How does spironolactone treat acne and unwanted hair from polycystic ovary syndrome (PCOS)?
- When is metformin used for polycystic ovary syndrome (PCOS)?