Ovarian hyperstimulation syndrome

Clinical Features: Ovarian hyperstimulation syndrome (OHSS) is a potentially life-threatening complication of ovarian stimulation, particularly following assisted conception treatments. The clinical presentation varies by severity:

• Mild OHSS: abdominal bloating and mild abdominal pain.
• Moderate OHSS: nausea, vomiting, and increased abdominal discomfort.
• Severe OHSS: oliguria, generalized oedema, significant abdominal pain and/or distension due to enlarged ovaries and acute ascites, and occasionally hydrothorax.
• Critical OHSS: oligo/anuria, tense ascites or large hydrothorax, thromboembolism, and acute respiratory distress syndrome.

Other symptoms may overlap with complications such as ovarian cyst torsion, haemorrhage, pelvic infection, or ectopic pregnancy, which should be considered in differential diagnosis.

Diagnostic Methods: Diagnosis is primarily clinical, based on symptom severity and history of ovarian stimulation. Ultrasound imaging is essential to assess ovarian size, presence of ascites, and pleural effusions. Laboratory tests may include hematocrit (to detect hemoconcentration), renal function tests, electrolytes, and coagulation profile to evaluate severity and complications. Differential diagnoses such as ovarian cyst complications, pelvic infections, intra-abdominal hemorrhage, ectopic pregnancy, bowel perforation, or appendicitis must be excluded. Close monitoring is crucial as OHSS severity can worsen over time.

Management Strategies: Management depends on severity:

• Mild to moderate OHSS: outpatient management with symptomatic treatment including analgesia, antiemetics, and careful fluid balance monitoring.
• Severe to critical OHSS: hospital admission is required for close monitoring, intravenous fluid management to maintain circulatory volume, correction of electrolyte imbalances, thromboprophylaxis due to increased thromboembolism risk, and respiratory support if needed.
• Paracentesis may be necessary for tense ascites or large pleural effusions to relieve symptoms.
• Early recognition and referral to specialist units are essential for severe cases.
• Prevention strategies during ovarian stimulation include using the lowest effective dose of gonadotrophins, ultrasound monitoring of follicular development, and considering GnRH antagonist protocols to reduce risk.
• Use of GnRH agonist trigger instead of hCG in high-risk patients can reduce OHSS incidence.

Patients should be informed about the risks of OHSS before starting ovarian stimulation. The severity of OHSS can progress even if initial symptoms are mild, so ongoing vigilance is necessary.

This integrated approach aligns with UK NICE and RCOG guidelines and is supported by recent literature emphasizing the importance of early detection, risk stratification, and individualized management to reduce morbidity and mortality associated with OHSS.

References: ¹, (Gullo et al., 2024)