Ovarian Hyperstimulation Syndrome: What It Is and How It Is Treated

Written by Medicover Team and Medically Reviewed by Dr Sharayu Mirji , Gynecologists

Ovarian Hyperstimulation Syndrome (OHSS) is a complication that can occur during fertility treatment, especially after medicines used to stimulate the ovaries to produce multiple eggs. Mild OHSS is relatively common and usually improves with monitoring and supportive care, while severe cases can cause significant fluid buildup, dehydration, blood clots, and kidney problems. Early recognition and appropriate medical care can help prevent serious complications.

What Are the Symptoms of Ovarian Hyperstimulation Syndrome?

Ovarian Hyperstimulation Syndrome symptoms vary depending on the severity of the condition and may develop within days after ovarian stimulation or egg retrieval. Symptoms can range from mild abdominal discomfort to serious complications requiring hospital care.

Mild OHSS Symptoms

• Abdominal bloating and mild pain
• Nausea and occasional vomiting
• Diarrhea
• Slight weight gain

Moderate OHSS Symptoms

• Noticeable abdominal swelling
• Persistent nausea and vomiting
• Rapid weight gain
• Reduced urine output

Severe OHSS Symptoms

• Severe abdominal pain or swelling
• Significant and rapid weight gain
• Shortness of breath due to fluid accumulation around the lungs
• Dehydration
• Very low urine output
• Blood clots, which are uncommon but potentially serious

What Are the Causes of Ovarian Hyperstimulation Syndrome (OHSS)?

OHSS occurs when the ovaries respond too strongly to fertility medicines, particularly injectable gonadotropins. The stimulated ovaries release substances that increase blood vessel permeability, allowing fluid to move into the abdomen and, in severe cases, the chest.

Common Causes

• Strong ovarian response to fertility medicines: Some women develop a greater-than-expected response to ovarian stimulation.
• hCG exposure: Human chorionic gonadotropin (hCG), used to trigger ovulation in some fertility treatment cycles, can contribute to the development or worsening of OHSS.
• Development of multiple follicles: Producing a large number of follicles can increase ovarian enlargement and the risk of OHSS.
• High estrogen levels: High estradiol levels during ovarian stimulation are associated with an increased risk of OHSS.
• Pregnancy after treatment: If pregnancy occurs, naturally produced hCG can cause OHSS to persist or become more severe.

When to See a Doctor for Ovarian Hyperstimulation Syndrome?

Contact your fertility specialist or gynecologist if you develop abdominal swelling, pain, nausea, vomiting, or rapid weight gain after fertility treatment. Early assessment helps determine the severity of OHSS and reduces the risk of complications.

Get immediate medical help if:

A fertility specialist or reproductive medicine specialist usually evaluates and treats OHSS. A gynecologist may also manage the condition, while an obstetrician may be involved when OHSS occurs during early pregnancy. Severe cases may require care from emergency, critical care, nephrology, or other specialists depending on the complications.

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How Is Ovarian Hyperstimulation Syndrome Diagnosed?

OHSS is diagnosed using symptoms, medical history, physical examination, and tests that assess ovarian enlargement, fluid accumulation, blood concentration, and organ function. The severity of the condition determines how closely a patient needs to be monitored.

Methods Used to Diagnose OHSS

• Physical Examination: Doctors assess abdominal swelling, tenderness, pain, blood pressure, heart rate, and breathing.
• Ultrasound: Pelvic ultrasound can show enlarged ovaries, multiple follicles, and fluid accumulation in the abdomen.
• Blood Tests: Blood tests can assess blood concentration, electrolyte levels, kidney function, and other changes associated with severe OHSS. Hormone levels may also be monitored during fertility treatment.
• Chest Imaging: A chest X-ray or other imaging may be used when breathing problems suggest fluid accumulation around the lungs.
• Weight and Urine Monitoring: Daily weight and urine output can help identify worsening fluid shifts and dehydration.

What Are the Treatment Options for Ovarian Hyperstimulation Syndrome?

Ovarian Hyperstimulation Syndrome treatment depends on its severity. Mild cases usually improve with monitoring and supportive care, while moderate or severe OHSS may require close medical observation or hospitalization. Treatment aims to maintain fluid balance, control symptoms, and prevent complications such as blood clots and kidney problems.

Mild OHSS Treatment

• Rest and adequate fluid intake according to medical advice
• Avoiding strenuous exercise and activities that may increase the risk of ovarian injury
• Pain relief with medicines recommended by the doctor
• Monitoring body weight, symptoms, and urine output
• Regular follow-up to ensure symptoms are not worsening

Moderate OHSS Treatment

• Closer medical monitoring of symptoms, weight, urine output, and blood tests
• Fluid and electrolyte management based on individual needs
• Adjustment or stopping of fertility medicines when appropriate
• Monitoring for complications such as dehydration, kidney problems, or blood clots

Severe OHSS Treatment

Severe OHSS may require hospitalization for close monitoring and treatment of complications.

• Intravenous fluids when needed to maintain hydration and circulation
• Medication to reduce the risk of blood clots when clinically indicated
• Paracentesis to remove abdominal fluid when severe fluid accumulation causes significant discomfort or breathing problems
• Oxygen support if breathing is affected
• Monitoring and treatment of kidney function and electrolyte abnormalities
• Careful monitoring for blood clots and other serious complications

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What Diet Is Recommended for Ovarian Hyperstimulation Syndrome?

There is no specific diet that cures OHSS. During recovery, nutrition and fluid intake should be individualized according to the severity of symptoms and your doctor's advice. Patients with moderate or severe OHSS may need careful monitoring of fluid and electrolyte balance.

• Drink fluids according to your doctor's recommendations.
• Eat small, frequent meals if abdominal swelling or nausea makes large meals uncomfortable.
• Include adequate protein and a balanced variety of foods to support nutritional needs.
• Choose fiber-rich foods if constipation occurs, unless your doctor advises otherwise.
• Avoid excessive alcohol and foods that worsen nausea or abdominal discomfort.

How Can Ovarian Hyperstimulation Syndrome Be Prevented?

OHSS prevention focuses on identifying women at higher risk and carefully controlling ovarian stimulation. Fertility specialists can adjust medicines and treatment protocols based on the ovarian response.

• Use individualized doses of fertility medicines.
• Monitor ovarian response with ultrasound and blood tests during stimulation.
• Use an appropriate ovulation-triggering medicine based on the patient's risk of OHSS.
• Consider a freeze-all embryo strategy in selected high-risk patients to reduce the risk of late-onset OHSS.
• Use preventive medicines or other treatment adjustments when clinically appropriate.
• Follow the fertility team's instructions for monitoring symptoms after egg retrieval or embryo transfer.
• Report rapid weight gain, increasing abdominal swelling, reduced urine output, or breathing problems promptly.

What Are the Risk Factors for Ovarian Hyperstimulation Syndrome?

Certain factors can increase the likelihood of developing OHSS during fertility treatment. Identifying these factors allows fertility specialists to adjust treatment and provide closer monitoring.

• Previous history of OHSS
• Polycystic ovary syndrome (PCOS)
• Young age, particularly under 35 years
• High ovarian reserve or a large number of developing follicles
• High estradiol levels during ovarian stimulation
• Previous strong response to fertility medicines
• Use of certain hCG-based ovulation triggers
• Pregnancy following ovarian stimulation, which can contribute to late-onset OHSS

What Are the Complications of Ovarian Hyperstimulation Syndrome?

Most cases of OHSS are mild, but severe OHSS can cause serious complications and requires prompt medical care.

• Severe dehydration and electrolyte imbalance
• Fluid accumulation in the abdomen or around the lungs
• Kidney dysfunction
• Blood clots
• Breathing difficulties
• Ovarian torsion, which can occur when enlarged ovaries twist
• Rarely, severe organ complications that require intensive medical care