PCOS (polycystic ovary syndrome)

Written by Zayn Miah & R KhanomLast updated 17 September 2026Not clinically reviewed

A hormonal condition affecting ovulation, associated with multiple small follicles on the ovaries and, often, irregular periods.

In plain English

It's a common hormonal condition that can make ovulation irregular or absent, and it can affect how your ovaries respond to stimulation drugs.

Why it matters

People with PCOS often respond strongly to stimulation medication, so they're monitored closely for a higher risk of OHSS.

Related terms

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Written by patients, not clinicians. This page has not yet been reviewed by a named fertility professional, so it explains published guidance and points you to the original source instead of giving medical advice. It is not medical advice. Decisions about your treatment belong with your own clinic. Read our editorial policy and corrections policy.