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Ovarian Hyperstimulation Syndrome (OHSS) is a potentially serious complication of fertility treatments that is often misunderstood, underestimated, and underreported. In today’s world of increasing reliance on assisted reproductive technologies (ART) such as in vitro fertilization (IVF), it’s essential for women and families to understand what OHSS is, how to prevent it, and what to expect if it occurs.

📈 Global data suggests that mild to moderate OHSS affects up to 20–30% of women undergoing IVF, while severe forms occur in less than 1–2% of cycles. In India, due to limited surveillance, the real numbers may be underrepresented, but with over 3.5 lakh IVF cycles per year, thousands of women are at potential risk.

Let’s explore this condition in depth.

What is Ovarian Hyperstimulation Syndrome (OHSS)?

OHSS is an iatrogenic where the female need to be treated with fertility medications to produce large number of eggs. While the goal is to improve the chances of pregnancy, in some women, this stimulation becomes excessive.

In OHSS, the ovaries will enlarge and start leaking the fluid into the abdomen and if it becomes serious, the liquid will leak on the chest cavity. This fluid shift results in bloating, pain, and serious complications like dehydration, blood clots, and organ dysfunction.

Why Does OHSS Happen?

The main culprit behind OHSS is human chorionic gonadotropin (hCG) – a hormone commonly used in IVF cycles to trigger the final maturation of eggs before retrieval.

When hCG is administered, it stimulates the ovaries to produce high levels of vascular endothelial growth factor (VEGF). VEGF increases blood vessel permeability, which causes fluid to leak into surrounding body cavities.

Women who get pregnant in the same IVF cycle are at higher risk because pregnancy itself causes a rise in natural hCG, prolonging OHSS symptoms.

How Common is OHSS?

According to the American Society for Reproductive Medicine (ASRM), over 10% of IVF cycles used to be complicated by OHSS before modern prevention strategies were adopted.

Risk Factors: Who is Most at Risk?

Some women are more prone to developing OHSS. These include:

• Women with Polycystic Ovary Syndrome (PCOS)
• Age below 30
• Low BMI
• High Anti-Müllerian Hormone (AMH) levels  which is greater than 3.5 ng/ml
• A high number of ovarian follicles (>15–20)
• Rapidly rising estradiol levels (>3500 pg/mL)
• Prior history of OHSS
• Pregnancy during same cycle (increases severity)

Studies show that up to 50% of women with PCOS undergoing IVF may experience some degree of OHSS if not properly monitored.

What are the Symptoms of OHSS?

Symptoms typically show up within 4–7 days after the ovulation trigger shot and may worsen if pregnancy occurs.

Mild to Moderate OHSS Symptoms

• Abdominal bloating
• Mild to moderate abdominal pain
• Nausea and vomiting
• Diarrhea
• Weight gain (1–2 kg in a few days)
• Ovarian tenderness

Severe OHSS Symptoms

• Sudden weight gain i.e., more than 2 kg in 24 hours
• Severe abdominal pain and swelling
• Reduced urination
• Dark-colored urine
• Shortness of breath
• Rapid heartbeat
• Blood clots (leg pain, swelling)
• Pleural effusion (fluid in chest cavity)

How is OHSS Diagnosed?

Your fertility team will usually diagnose OHSS based on:

• Medical history and fertility treatment plan
• Physical exam (abdominal size, tenderness)
• Ultrasound (shows enlarged ovaries, ascitic fluid)
• Blood tests: Helps to monitor estradiol levels, hematocrit, WBC count, and kidney function,etc.,
• Chest X-ray or CT scan

Treatment: How is OHSS Syndrome Managed?

Mild OHSS:

Usually managed at home with:

• Oral fluids (preferably electrolyte-rich like ORS)
• Rest (but not complete bedrest – to avoid clots)
• Daily weight tracking
• Pain relief (e.g. paracetamol)
• Monitoring for worsening symptoms

Moderate OHSS:

• May require outpatient visits or short hospital stays
• Intravenous fluids
• Blood tests
• Ultrasounds to monitor fluid buildup
• Anticoagulants (blood thinners like heparin)

Severe OHSS:

Hospitalization is mandatory, often in an ICU setting:

• Intravenous albumin
• Paracentesis (to drain abdominal fluid)
• Oxygen therapy
• Dialysis
• Monitoring for blood clots, pleural effusion

Can OHSS Be Prevented?

Absolutely. With careful cycle planning and newer protocols, the risk of OHSS can be drastically reduced.

Prevention Strategies

1. Low-dose Stimulation: Start with minimal effective doses of gonadotropins.
2. GnRH Antagonist Protocols: These newer regimens lower OHSS risk compared to older GnRH agonist protocols.
3. GnRH Agonist Trigger: Replacing hCG with a GnRH agonist for ovulation trigger significantly lowers OHSS risk.
4. Cabergoline (Dopamine Agonists): Lowers VEGF activity and vascular permeability.
5. Freeze-All Strategy: Freezing all embryos and deferring transfer reduces the chance of late-onset OHSS due to pregnancy.
6. Avoid hCG for Luteal Phase Support: Use progesterone instead.
7. Metformin for PCOS Patients: Particularly effective in women undergoing GnRH agonist cycles.
8. Frequent Ultrasounds + Blood Work: With close monitoring, we can detect early signs to prevent the syndrome.

💡 ASRM 2024 guidelines recommend a combination of individualized gonadotropin dosing, GnRH antagonist protocols, and freeze-all cycles in high-risk patients.

What Happens After Treatment?

Post-Treatment Guidelines

• Follow-up scans to confirm resolution
• Continue blood thinners if advised (especially in pregnancy)
• Avoid heavy activity or sexual intercourse until ovaries return to normal size
• Hydration is key: maintain 2–3 liters of oral fluid daily

Will OHSS Affect My Pregnancy?

Not typically. But, severe cause can increase the risk of:

• Pre-eclampsia
• Preterm birth
• Low birth weight

Will It Happen Again?

If you’ve had OHSS once, you’re more likely to experience it again. Inform your fertility team so they can customize future cycles to minimize risk.

Final Thoughts

Ovarian Hyperstimulation Syndrome may sound scary, but it’s both predictable and preventable. As ART becomes more common in India and globally, awareness about OHSS is crucial—not just for doctors, but for every woman embarking on her fertility journey.

By choosing a reputed fertility clinic, being informed about your risk factors, and following a personalized stimulation plan, you can greatly reduce your chances of experiencing OHSS.