Mild OHSS - Diagnosis and Treatment

Background / Pathophysiology

• Ovarian enlargement and fragility
• Extravascular fluid accumulation (third-spacing)
• Intravascular volume depletion

• Early OHSS: 3-7 days after hCG trigger; related to exogenous hCG
• Late-onset OHSS: 12-17 days after trigger; driven by endogenous hCG from early pregnancy; tends to be more severe, especially with multiple gestation

Severity Classification (Golan/Navot Criteria)

Diagnosis of Mild OHSS

• Abdominal bloating and distension (grade 1)
• Nausea, vomiting, or diarrhea (grade 2)
• Ovarian enlargement (grade 2: ≥5 cm diameter on ultrasound)
• No ascites visible on imaging

• Pelvic ultrasound - to measure ovarian size; no significant peritoneal/pleural fluid in mild disease
• Serial weight monitoring (weight gain >2 lb/day signals worsening)
• If uncertain about severity: CBC (hemoconcentration?), electrolytes (hyponatremia/hyperkalemia?), renal function, LFTs

Risk Factors

• Polycystic ovary syndrome (PCOS) or polycystic ovarian morphology
• Elevated AMH (>3.36 ng/mL)
• Previous OHSS episode
• Estradiol >3,500 pg/mL at time of hCG trigger

• 20 preovulatory follicles on monitoring

• ≥20-29 oocytes retrieved (severe OHSS risk rises sharply with ≥30 oocytes)

Treatment of Mild OHSS

1. Activity restriction - limit strenuous physical activity
2. Fluid intake - at least 1 L/day of mostly electrolyte-balanced fluids (sports drinks, oral rehydration solutions preferred over plain water)
3. Daily weight monitoring - patient self-weighs each morning
4. Fluid balance monitoring - patient tracks urine output
5. Daily telephone or clinic follow-up - reassess symptoms

• Inability to tolerate oral hydration
• Hemodynamic instability
• Respiratory compromise
• Tense ascites
• Hemoconcentration (hematocrit rising)
• Leukocytosis
• Hyponatremia or hyperkalemia
• Weight gain >2 lb/day

• Antiemetics for nausea/vomiting (e.g., ondansetron, metoclopramide)
• Analgesics for discomfort (paracetamol preferred; avoid NSAIDs which may worsen renal perfusion in at-risk patients)

• No IV fluids or albumin infusions needed (these are reserved for moderate-severe)
• No paracentesis needed
• No thromboprophylaxis routinely unless additional VTE risk factors exist

Natural Course

• Berek & Novak's Gynecology, pp. 2100-2101 (Severity Classification, Risk Factors, Management)
• Tintinalli's Emergency Medicine: A Comprehensive Study

Mild OHSS - Diagnosis and Treatment

Pathophysiology (Brief)

• VEGF (vascular endothelial growth factor) - upregulated in granulosa cells by hCG - is the primary driver
• Angiotensin, inflammatory cytokines, renin/prorenin from follicular fluid all contribute
• Result: ovarian enlargement + extravascular fluid accumulation + intravascular volume depletion

• Early OHSS: 3-7 days post-hCG trigger; driven by exogenous hCG
• Late-onset OHSS: 12-17 days post-trigger; driven by endogenous hCG from early pregnancy; more severe, especially with multiple gestation

Severity Classification (Golan/Navot Criteria)

Diagnosis of Mild OHSS

• Pelvic ultrasound - confirms ovarian enlargement; rules out ascites (which would upgrade to moderate)
• Daily weight - weight gain >2 lb/day signals progression
• Fluid balance - intake and urine output monitoring
• If severity is uncertain: CBC (hematocrit for hemoconcentration), electrolytes, renal function, LFTs

• Mild vs Moderate = presence of sonographic ascites (pocket >9 mm)
• Moderate vs Severe = ascites becomes clinically detectable + respiratory/hemodynamic symptoms

Risk Factors

• PCOS or polycystic ovarian morphology
• Elevated AMH (>3.36 ng/mL)
• Previous OHSS episode
• E2 >3,500 pg/mL at hCG trigger (1.5% risk of severe OHSS; rises to 38% if E2 >6,000 pg/mL)
• >20 preovulatory follicles (15% severe OHSS risk)
• ≥20-29 oocytes retrieved (1.4% severe risk; rises to 22.7% with ≥30 oocytes)

Treatment of Mild OHSS

Outpatient Management

1. Activity restriction - avoid strenuous exercise; gentle walking is acceptable
2. Oral hydration - at least 1 L/day of electrolyte-balanced fluids (oral rehydration salts, sports drinks preferred over plain water to avoid dilutional hyponatremia)
3. Daily self-monitoring:
   • Weigh every morning (same time, same clothing)
   • Track fluid intake and urine output
4. Daily follow-up - telephone check-in or clinic visit; reassess if symptoms worsen

Symptomatic Relief

• Nausea/vomiting: antiemetics (ondansetron, metoclopramide)
• Pain/discomfort: paracetamol/acetaminophen preferred
  • Avoid NSAIDs - can worsen renal perfusion, which matters if hemoconcentration develops
• Avoid pelvic/abdominal trauma (enlarged ovaries are fragile and at risk of torsion)

What is NOT Needed in Mild OHSS

• No IV fluids or albumin infusions (reserved for moderate-severe)
• No paracentesis
• No routine thromboprophylaxis (unless additional VTE risk factors exist)
• No cycle cancellation (in mild disease)

When to Escalate - Red Flags Requiring Hospitalization

Natural Course

• In non-pregnant cycles: resolves in 7-10 days as follicles regress and hCG levels fall
• If pregnancy occurs (especially multiple gestation): symptoms can persist or worsen into late-onset OHSS - continue close surveillance through early first trimester

• Berek & Novak's Gynecology, pp. 2100-2101 (Severity Classification, Risk Factors, Management)
• Tintinalli's Emergency Medicine: A Comprehensive Study (OHSS clinical overview)

Treatment of Mild OHSS

1. Activity Restriction

• Limit physical activity
• Avoid strenuous exercise and sexual intercourse (enlarged ovaries are fragile and prone to torsion or rupture)
• Bed rest is not required, gentle ambulation is fine

2. Oral Hydration

• Minimum 1 L/day of fluid
• Prefer electrolyte-balanced fluids (oral rehydration salts, sports drinks like Gatorade) over plain water
• Plain water in large amounts can worsen dilutional hyponatremia

3. Symptomatic Relief

4. Daily Monitoring (Patient Self-Monitoring)

• Daily weight - same time each morning
• Fluid intake - record how much is drunk
• Urine output - ensure adequate output
• Symptom diary - note any worsening bloating, breathlessness, or leg pain

5. Daily Medical Follow-Up

• Telephone check-in or clinic visit every day
• Reassess immediately if:
  • Weight gain >2 lb (approximately 1 kg) per day
  • Symptoms are worsening
  • Unable to keep fluids down
  • Breathlessness, chest pain, or leg swelling develops

What is NOT Used in Mild OHSS

Natural Course and Resolution

• Without pregnancy: resolves in 7-10 days as follicular cysts regress and hCG levels decline
• With pregnancy (especially multiple gestation): late-onset OHSS can develop 12-17 days post-trigger, driven by endogenous hCG - continue close follow-up through early first trimester

Red Flags - When to Escalate to Inpatient Care

• Unable to tolerate oral hydration
• Weight gain >2 lb/day
• Hemodynamic instability (hypotension, tachycardia)
• Respiratory distress or falling oxygen saturation
• Tense or clinically detectable ascites
• Rising hematocrit (hemoconcentration)
• Oliguria
• Hyponatremia or hyperkalemia
• Abnormal renal or liver function tests
• Leukocytosis