PCOS is a hormonal imbalance affecting roughly one in ten women of reproductive age. The ovaries develop many small follicles (sacs that hold eggs) that don't mature and release an egg on schedule. So ovulation becomes irregular or stops, which is why periods become unpredictable and getting pregnant can take longer.
A note on names: In May 2026, an international group led by Monash University renamed PCOS to Polyendocrine Metabolic Ovarian Syndrome (PMOS). Only the name changed. The diagnosis, criteria, and care are the same. The new name better reflects that this is a hormonal and metabolic condition, not a disease of ovarian cysts. Major hospitals (Mayo Clinic, Cleveland Clinic, Johns Hopkins) have already updated their pages to PMOS. This site keeps "PCOS" in titles and body text because that's what most people still search for. Everything here applies under either name.
Common signs
Irregular or missed periods, acne or oily skin, excess facial or body hair, weight gain that's hard to shift (especially around the belly), and thinning scalp hair. Symptoms can appear years before diagnosis, and not everyone has all of them — PCOS looks different in different women.
PCOS and fertility
PCOS does not mean pregnancy is out of reach. Because the main issue is irregular ovulation, treatment focuses on restoring it: lifestyle and nutrition changes, medicines that induce ovulation, and IVF where needed. With the right treatment plan, most women with PCOS can conceive.