OHSS (ovarian hyperstimulation syndrome)
A condition in which the ovaries become swollen and painful in response to fertility hormones, ranging from mild to severe.
In plain English
It's a reaction to stimulation medication where your ovaries swell up and can cause fluid to build up, ranging from mild discomfort to a serious medical condition.
Why it matters
It's why your clinic monitors you closely during stimulation and may adjust your trigger shot or freeze all embryos rather than doing a fresh transfer.
Related terms
Guides that cover this
Sources
- IVF: what is IVF and how does it work?, HFEA (UK fertility regulator). Link checked 17 September 2026.
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.