40w LaterGuide

Ovarian hyperstimulation syndrome (OHSS) is a potential complication of ovarian stimulation used in IVF and other fertility treatments. Most cases are mild, but in rare cases OHSS can become severe and require medical treatment.

Why does OHSS happen?

During IVF, medications are used to stimulate the ovaries so that multiple follicles can develop at the same time. Some people respond more strongly than expected and develop a large number of follicles.

OHSS is associated with substances such as vascular endothelial growth factor (VEGF), which increase the permeability of blood vessels. This can cause fluid to move out of the bloodstream and collect elsewhere in the body, particularly in the abdomen.

In more severe cases, fluid can also collect around the lungs, while the amount of fluid circulating in the bloodstream decreases. This can affect kidney function and increase the risk of blood clots and other serious complications.

Who has a higher risk?

The risk is higher in people who have a strong response to ovarian stimulation. Factors associated with increased risk include:

• Polycystic ovary syndrome (PCOS)
• A high ovarian reserve, such as a high AMH level or antral follicle count
• Development of a large number of follicles during stimulation
• A high number of eggs retrieved
• A previous history of OHSS

Your fertility team monitors your response during treatment and may adjust the treatment plan if your risk appears to be increasing.

When can OHSS occur?

Symptoms often develop within several days after the medication used to trigger final egg maturation. This is sometimes called early-onset OHSS.

OHSS can also develop or become worse later, particularly if pregnancy occurs, because the pregnancy hormone hCG can continue to stimulate the processes involved in OHSS. This is known as late-onset OHSS and symptoms may last longer.

What symptoms should you watch for?

Symptoms can include:

• Abdominal bloating or discomfort
• Abdominal pain
• Nausea or vomiting
• Rapid increase in abdominal size or body weight
• Reduced urination
• Shortness of breath

Contact your fertility clinic if symptoms are worsening. Seek urgent medical attention for severe or rapidly worsening abdominal pain, significant shortness of breath, very little or no urine, fainting, chest pain, or other severe symptoms.

Can OHSS be prevented?

The risk cannot always be eliminated completely, but modern IVF protocols can substantially reduce it.

Depending on your individual risk and response to stimulation, your fertility specialist may adjust the dose or type of stimulation medication, use a GnRH antagonist protocol, choose a GnRH agonist rather than hCG for final oocyte maturation in appropriate cycles, prescribe medication such as cabergoline, or freeze all suitable embryos and postpone embryo transfer.

A freeze-all strategy can help prevent pregnancy-related hCG from worsening OHSS. A frozen embryo transfer can then be planned after your ovaries and body have recovered.

How is OHSS treated?

Treatment depends on how severe the condition is. Mild cases can often be monitored at home with instructions from the fertility clinic. Your healthcare team may ask you to monitor symptoms, weight, fluid intake and urine output.

More significant OHSS may require blood tests, ultrasound, intravenous fluids or other medical treatment. Severe cases may require hospital care. If a large amount of fluid has accumulated in the abdomen and is causing significant discomfort or breathing problems, drainage of the fluid may be considered. Measures to prevent or treat blood clots may also be necessary for some patients.

Do not start aspirin, anticoagulants, or other medications, or follow a fixed fluid-drinking regimen, on your own to treat OHSS. Management should be based on your symptoms and medical assessment.

OHSS usually improves with time, but severe OHSS can be serious. If you are undergoing ovarian stimulation, follow the monitoring schedule and contact your fertility clinic promptly if you develop concerning symptoms.