Mastering Ovarian Hyperstimulation Syndrome Guidelines for SCE Obstetrics & Gynaecology Success

Introduction

Ovarian Hyperstimulation Syndrome (OHSS) remains one of the most serious iatrogenic complications of assisted reproductive technology (ART). For SCE Obstetrics & Gynaecology candidates, understanding the prevention, diagnosis, and management of OHSS is crucial for both exam success and clinical practice. This comprehensive guide covers the latest NICE-endorsed guidelines and essential management strategies.

What is Ovarian Hyperstimulation Syndrome?

OHSS is a potentially life-threatening condition characterized by massive ovarian enlargement and fluid shift from intravascular to third spaces, leading to ascites, pleural effusion, and haemoconcentration. It typically occurs following administration of gonadotropins for ovarian stimulation in IVF cycles.

Classification and Grading

Mild OHSS

• Abdominal distension

• Mild abdominal pain

• Ovarian size <8 cm

• Nausea and vomiting

Moderate OHSS

• Moderate abdominal pain

• Ovarian size 8-12 cm

• Ascites on ultrasound

• Haematocrit >45%

Severe OHSS

• Severe abdominal pain

• Ovarian size >12 cm

• tense ascites

• Haematocrit >55%

• Oliguria

• Creatinine >1.6 mg/dL

• Thromboembolism

Critical OHSS

• Critical ovarian enlargement

• Severe hydrothorax

• ARDS

• Renal failure

• Thromboembolic events

Prevention Strategies

Patient Risk Assessment

• Young age (<35 years)

• Polycystic ovary syndrome (PCOS)

• Previous OHSS history

• High anti-Müllerian hormone (AMH) levels

• Large number of follicles retrieved

Pharmacological Prevention

1. Coasting (Ovarian Suspension): Withhold gonadotropins when lead follicles reach 14-16 mm while continuing GnRH agonist/an antagonist

2. Metformin: Pre-treatment in PCOS patients

3. Dopamine Agonists: Cabergoline or quinagolide from the day of hCG administration

4. Aspirin: Low-dose aspirin for thromboprophylaxis

5. GnRH Antagonist Protocol: Preferred over agonist protocols

Cycle Cancellation

Consider cancelling the embryo transfer and freezing all embryos in high-risk patients.

Management Guidelines

Conservative Management (Mild-Moderate OHSS)

• Rest and limited physical activity

• Fluid balance monitoring

• Analgesia (paracetamol, avoiding NSAIDs)

• Anti-emetics

• Compression stockings

• Thromboprophylaxis (LMWH if immobile)

Moderate to Severe OHSS - Hospital Admission Criteria

• Severe abdominal pain

• Persistent nausea/vomiting

• Oliguria

• Dyspnoea

• Rapid weight gain (>1 kg/day)

• Haematocrit >50%

• Electrolyte imbalance

• Ovarian size >12 cm

In-Patient Management

Fluid Management:

• Crystalloids (normal saline) for intravascular volume expansion

• Avoid hypotonic fluids initially

• Monitor fluid balance hourly

• Aim for urine output >0.5 ml/kg/hour

Thromboprophylaxis:

• LMWH (enoxaparin 40 mg daily)

• Continue until symptoms resolve

• Consider therapeutic anticoagulation if thromboembolic complications

Paracentesis:

• Indicated for tense ascites causing pain or respiratory compromise

• Transvaginal ultrasound-guided drainage preferred

• Slow drainage to prevent hypotension

• Consider albumin replacement if large volume drainage

Ovine Discharge Criteria:

• Stable haematocrit

• Normal renal function

• No respiratory symptoms

• Able to maintain oral hydration

• No signs of infection

Key Points for SCE Examination

1. Prevention is Key: Identify high-risk patients early and implement preventive strategies

2. Monitor Strictly: Daily weight, abdominal girth, fluid balance, haematocrit

3. Early Intervention: Don't delay hospitalization in severe cases

4. Ovarian Size: >12 cm indicates severe OHSS

5. Haematocrit: >55% indicates severe disease

6. Thromboembolism: Leading cause of mortality - prioritize thromboprophylaxis

7. Frozen Embryo Transfer: Consider in high-risk patients to prevent pregnancy-associated worsening

Summary

OHSS remains a significant challenge in reproductive medicine. For SCE success, remember the triad of prevention, early identification, and appropriate supportive management. Always assess risk factors before stimulation and implement individualized strategies. The key to managing severe OHSS lies in aggressive fluid resuscitation, careful monitoring, and timely intervention with paracentesis when indicated.

This guide is aligned with NICE guidelines and current best practices for OHSS management. For more high-yield Obstetrics & Gynaecology topics, explore our SCE preparation resources.