Ovarian Hyperstimulation Syndrome: Symptoms, Causes & Treatment
Tests & Procedures

Ovarian Hyperstimulation Syndrome: Symptoms, Causes & Treatment

Ovarian Hyperstimulation Syndrome (OHSS) is a medical condition that can occur in women undergoing fertility treatments, particularly those involving ovarian stimulation. While fertility treatments have helped many women achieve pregnancy, they can sometimes lead to complications like OHSS, which can range from mild to severe. Understanding the signs and symptoms, causes, and treatment options for OHSS is crucial for managing the condition effectively and ensuring the safety of women undergoing fertility treatments.

What is Ovarian Hyperstimulation Syndrome?

OHSS is a condition that occurs when the ovaries become swollen and painful due to an excessive response to fertility medications used to stimulate the ovaries. These medications are often used in assisted reproductive technologies (ART) such as in vitro fertilization (IVF) to induce the production of multiple eggs. OHSS can cause the ovaries to enlarge and leak fluid into the abdomen, leading to various symptoms and complications.

Signs and Symptoms of OHSS

The symptoms of OHSS can vary from mild to severe, and they usually develop within a week of taking fertility medications. In some cases, symptoms can appear later, especially if pregnancy occurs. OHSS is classified into three categories: mild, moderate, and severe.


  • Abdominal Discomfort: Mild pain or discomfort in the lower abdomen.
  • Bloating: Swelling and a feeling of fullness in the abdomen.
  • Nausea: Mild nausea without vomiting.

Moderate OHSS

  • Increased Abdominal Pain: More pronounced pain and discomfort in the lower abdomen.
  • Bloating: Increased abdominal swelling and a sensation of fullness.
  • Nausea and Vomiting: Nausea accompanied by occasional vomiting.
  • Diarrhea: Loose stools or diarrhea.
  • Ovarian Enlargement: Noticeable enlargement of the ovaries, which can be confirmed through ultrasound.

Severe OHSS

  • Severe Abdominal Pain: Intense and persistent pain in the abdomen.
  • Significant Bloating: Extreme abdominal swelling and distension.
  • Severe Nausea and Vomiting: Persistent and severe nausea and vomiting.
  • Rapid Weight Gain: Rapid weight gain due to fluid accumulation (more than 2 pounds or 1 kilogram in 24 hours).
  • Shortness of Breath: Difficulty breathing due to fluid accumulation in the chest.
  • Decreased Urine Output: Reduced urine production despite adequate fluid intake.
  • Leg Swelling: Swelling in the legs and ankles.
  • Dizziness and Fainting: Lightheadedness and fainting spells.

Causes of Ovarian Hyperstimulation Syndrome

OHSS is primarily caused by an excessive response to fertility medications that stimulate the ovaries. The exact mechanism is not entirely understood, but several factors contribute to the development of OHSS:

  1. Hormonal Stimulation: Fertility medications, particularly human chorionic gonadotropin (hCG) used to trigger ovulation, can cause the ovaries to produce an excessive number of follicles. This overstimulation leads to increased vascular permeability and fluid leakage into the abdominal cavity.
  2. High Estrogen Levels: Elevated estrogen levels during ovarian stimulation can increase the risk of OHSS. High estrogen levels are often a result of the development of multiple follicles.
  3. Individual Susceptibility: Some women are more susceptible to OHSS due to their genetic makeup, underlying health conditions, or a history of OHSS in previous treatment cycles.
  4. Polycystic Ovary Syndrome (PCOS): Women with PCOS are at a higher risk of developing OHSS because they often have a higher baseline number of follicles and may over-respond to fertility medications.
  5. Young Age: Younger women, particularly those under 35, are more likely to experience OHSS as their ovaries tend to be more responsive to stimulation.

Diagnosis of OHSS

Diagnosing OHSS involves a combination of clinical evaluation, medical history, and diagnostic tests:

  1. Medical History and Physical Examination: The healthcare provider will review the patient’s medical history, including previous fertility treatments and any symptoms. A physical examination will assess abdominal swelling, pain, and overall health.
  2. Ultrasound: An ultrasound is performed to evaluate the size and number of ovarian follicles, as well as the presence of fluid in the abdomen.
  3. Blood Tests: Blood tests may be conducted to measure hormone levels, assess kidney and liver function, and check for signs of dehydration and electrolyte imbalances.

Treatment of OHSS

The treatment of OHSS depends on the severity of the condition. Mild cases often resolve on their own with supportive care, while moderate to severe cases require more intensive management.


  • Rest and Hydration: Increasing fluid intake and resting can help alleviate symptoms. Oral hydration is encouraged to maintain electrolyte balance.
  • Pain Relief: Over-the-counter pain relievers such as acetaminophen can be used to manage mild pain and discomfort.
  • Monitoring: Regular monitoring of symptoms and follow-up appointments with the healthcare provider are essential to ensure the condition does not worsen.

Moderate OHSS

  • Intravenous Fluids: In cases of moderate OHSS, intravenous (IV) fluids are administered to maintain hydration and electrolyte balance.
  • Anti-nausea Medications: Medications to control nausea and vomiting are prescribed.
  • Monitoring: Frequent monitoring of symptoms, ultrasound exams, and blood tests to assess kidney function and electrolyte levels.

Severe OHSS

  • Hospitalization: Severe OHSS often requires hospitalization for close monitoring and intensive treatment.
  • IV Fluids and Electrolytes: IV fluids and electrolytes are administered to manage dehydration and electrolyte imbalances.
  • Paracentesis: In cases of significant fluid accumulation in the abdomen, a procedure called paracentesis is performed to drain excess fluid and relieve pressure.
  • Thromboprophylaxis: To prevent blood clots, anticoagulant medications are prescribed.
  • Supportive Care: Oxygen therapy and other supportive measures are needed to manage complications such as difficulty breathing.

Prevention of OHSS

Preventing OHSS involves careful monitoring and management of ovarian stimulation during fertility treatments. Strategies to reduce the risk of OHSS include:

  1. Individualized Treatment Plans: Tailoring fertility treatment protocols to the individual patient’s needs and risk factors can help minimize the risk of OHSS.
  2. Low-Dose Stimulation Protocols: Using lower doses of fertility medications to stimulate the ovaries can reduce the risk of excessive ovarian response.
  3. GnRH Agonist Trigger: Replacing hCG with a gonadotropin-releasing hormone (GnRH) agonist trigger for ovulation can reduce the risk of OHSS.
  4. Coasting: Temporarily withholding fertility medications when estrogen levels are high to allow them to decrease before triggering ovulation.
  5. Freeze-All Strategy: Freezing all embryos and delaying embryo transfer to a later cycle can help prevent OHSS in high-risk patients.

Ovarian Hyperstimulation Syndrome is a potential complication of fertility treatments that can range from mild discomfort to severe and life-threatening symptoms. By closely monitoring patients and implementing preventive strategies, healthcare providers can minimize the risk of OHSS and help women achieve successful and safe fertility treatment outcomes.