IVF guide
Ovarian hyperstimulation syndrome (OHSS)
Ovarian hyperstimulation syndrome (OHSS) is an exaggerated response of the ovaries to stimulation medication. Most cases are mild, but severe cases need medical care.
What happens in OHSS
In OHSS, the ovaries become enlarged and fluid moves from the blood vessels into the abdomen. This can cause bloating and discomfort. In severe cases, fluid may also collect around the lungs and the blood can become more concentrated.2
Symptoms to watch for
- Bloating and abdominal discomfort
- Nausea or vomiting
- Rapid weight gain, for example more than 1 kg in a day
- Passing much less urine than usual
- Shortness of breath
If symptoms are severe or getting worse, the treating team should be contacted without delay.2 In an emergency in Turkey, call 112.
Who is at higher risk
- Women with polycystic ovary syndrome
- A high AMH or antral follicle count
- Many follicles or a high estradiol level during stimulation
- OHSS in a previous cycle1
How the risk is reduced
The physician may use a lower medication dose, an antagonist protocol, a different trigger injection or freeze all embryos and postpone the transfer.1 Close ultrasound and blood test monitoring helps adjust the plan.3
At home after egg collection
The team may advise drinking enough fluids, weighing yourself daily, noting how much urine you pass and avoiding strenuous activity.2 Follow the instructions of the treating team, as advice depends on the individual situation.
At a glance
- Symptoms usually start after egg collection.
- Mild bloating is common and often settles by itself.
- Severe symptoms need urgent medical assessment.
- The treatment plan is adjusted to reduce the risk.
Frequently asked questions
Usually in the days after egg collection. It can also start or worsen if pregnancy occurs.2
Mild symptoms are fairly common. Severe OHSS is less common.
OHSS does not harm frozen embryos. The transfer may be postponed to a later cycle.
References
- Practice Committee of the American Society for Reproductive Medicine. Prevention of moderate and severe ovarian hyperstimulation syndrome: a guideline. Fertility and Sterility. 2024;121(2):230–245.
- Royal College of Obstetricians and Gynaecologists. The Management of Ovarian Hyperstimulation Syndrome. Green-top Guideline No. 5. 2016.
- ESHRE Guideline Group on Ovarian Stimulation, Ata B, et al. ESHRE guideline: ovarian stimulation for IVF/ICSI: an update in 2025. Human Reproduction. 2026;41(4):498–514.
Related topics
This page gives general information only. It does not replace an examination, and the treatment plan is decided by the physician for each person individually.