Side Effects of Ovarian Hyperstimulation Syndrome (OHSS)
Ovarian hyperstimulation syndrome (OHSS) can cause serious and potentially life-threatening complications including venous thromboembolism, renal failure, and severe fluid shifts leading to significant morbidity and mortality. 1, 2
Classification and Clinical Manifestations
OHSS severity is typically categorized as:
Mild OHSS
- Abdominal bloating and discomfort
- Mild nausea
- Mild ovarian enlargement (5-12 cm)
- Weight gain (<5 kg)
Moderate OHSS
- Increased abdominal discomfort
- Nausea and vomiting
- Ultrasound evidence of ascites
- Moderate ovarian enlargement (8-12 cm)
- Weight gain (5-10 kg)
Severe OHSS
- Clinical ascites (sometimes with hydrothorax)
- Oliguria (<500 mL/day)
- Hemoconcentration (hematocrit >45%)
- Hypoproteinemia
- Significant ovarian enlargement (>12 cm)
- Electrolyte imbalances
- Severe abdominal pain
Critical OHSS
- Tense ascites or large hydrothorax
- Hematocrit >55%
- White blood cell count >25,000/mm³
- Oliguria or anuria
- Thromboembolism
- Acute respiratory distress syndrome
- Renal failure
Major Complications
1. Thromboembolism
- One of the most serious complications with potential for significant morbidity and mortality
- Risk of venous thrombosis up to 4.1% in severe OHSS 2
- Venous thrombosis more common than arterial events (predominantly in neck and upper extremity veins) 1
- Underlying thrombophilia increases risk of severe OHSS 1
2. Fluid and Electrolyte Imbalances
- Third-space fluid accumulation leading to:
- Ascites
- Pleural effusion
- Intravascular dehydration
- Hemoconcentration
- Electrolyte abnormalities (particularly hyponatremia)
3. Renal Complications
- Oliguria or anuria
- Acute kidney injury due to decreased renal perfusion
- Potential need for dialysis in severe cases
4. Respiratory Complications
- Pleural effusion
- Pulmonary edema
- Acute respiratory distress syndrome
- Dyspnea and tachypnea
5. Hepatic Dysfunction
- Elevated liver enzymes
- Impaired synthetic function
6. Adnexal Torsion
- Due to enlarged ovaries
- Presents with acute abdominal pain
- Surgical emergency
7. Neurological Manifestations
- Cerebral thrombosis (rare)
- Altered mental status due to electrolyte abnormalities
Risk Factors for OHSS
- Polycystic ovary syndrome
- Young age
- Low body weight
- High estradiol levels during ovarian stimulation
- Previous OHSS
- Multiple follicle development
- Pregnancy (especially multiple)
- Use of hCG for luteal support
Prevention and Management
Thromboprophylaxis
- LMWH prophylaxis (enoxaparin 40 mg daily) is recommended in severe OHSS 1, 2
- Start at beginning of ovarian stimulation, withhold 24-36 hours before oocyte retrieval, resume after retrieval 1
- Continue until estrogen levels return to near-physiologic levels if no pregnancy occurs 1
- For patients with antiphospholipid syndrome or history of thrombosis, therapeutic anticoagulation may be required 1, 2
Fluid Management
- Careful monitoring of fluid balance
- Intravenous crystalloids for intravascular volume replacement
- Albumin administration may be considered in severe cases
Paracentesis
- For severe ascites causing respiratory compromise or significant discomfort
- Can be performed transvaginally or transabdominally
- May prevent need for hospitalization in moderate-severe cases
Monitoring Parameters
- Daily weight
- Abdominal circumference
- Urine output
- Vital signs
- Complete blood count, electrolytes, liver and renal function tests
- Coagulation profile
Special Considerations
Patients with severe OHSS should be monitored closely for development of complications, particularly thromboembolism, which can occur up to 11 weeks after the initial presentation 1. The risk of complications is higher in patients who become pregnant following assisted reproductive technology.
Patients with underlying thrombophilia or history of thrombosis should receive special attention as they are at increased risk for thrombotic complications when OHSS develops 1.