Does PCOS increase miscarriage risk?

Note on the name: in May 2026, polycystic ovary syndrome (PCOS) was formally renamed polyendocrine metabolic ovarian syndrome (PMOS), following a global consensus process. The old name was inaccurate — the condition affects multiple hormone and metabolic systems, not just the ovaries, and "polycystic" wrongly implies ovarian cysts. Nothing about the condition, its diagnosis or its treatment has changed. Both names will be used side by side for the next few years, and we use PCOS below since that is the term most people know.

PCOS has been associated with a somewhat higher miscarriage rate than the general population, though the size of that increase varies between studies and much of it may be explained by associated factors rather than PCOS itself — particularly raised BMI and insulin resistance. What is worth doing before conceiving: optimising weight if you are overweight, checking and correcting thyroid function and vitamin D, and ensuring blood sugar is well controlled. These are worthwhile for pregnancy generally, not only for miscarriage risk. On metformin specifically: it is sometimes continued into early pregnancy in PCOS with the aim of reducing miscarriage. The evidence for this particular use is not strong, and practice varies considerably between clinicians. If it is suggested to you, ask what the expected benefit is in your specific case. Do not start, stop or continue it in pregnancy without your doctor's direction. Most importantly: if you have PCOS and have had a miscarriage, it was not caused by anything you did or failed to do. And having PCOS does not mean you should expect to miscarry — most women with PCOS who conceive go on to have a healthy pregnancy.