Table 1.

OHSS classification.

Symptoms Frequency	Always	Usually	Often	Rarely
Mild OHSS	Enlargement of bilateral ovaries with multiple follicular.	Corpus luteal cysts, measuring up to 8 cm.	Abdominal bloating and mild abdominal pain.
Moderate OHSS	Ovaries up to 12 cm.	Abdominal bloating due to an increase in ovarian size.	Gastrointestinal symptoms (nausea, vomiting and diarrhea).	Ultrasound evidence of ascites and rapid weight gain of over 2.5–3 kg.
Severe OHSS	Large ovarian cysts (>12 × 12 cm), clinical ascites with or without hydrothorax.	Hyperkalemia (potassium > 5 mmol/L), hyponatremia (sodium < 135 mmol/L).	Oliguria (<300 mL/d or <30 mL/h), creatinine 1.1–1.5 mg/dL, and hypovolemic shock. Hemoconcentration with hematocrit > 45%, white cell count > 15,000.	Liver dysfunction, increased blood viscosity, and thromboembolic.
Critical OHSS	Severe ascites or hydrothorax, hematocrit > 55%, white cell count > 25,000/mL.	Oliguria or anuria, creatinine ≥ 1.6 mg/dL, creatinine clearance < 50 mL/min.	Thromboembolism, or acute respiratory distress syndrome.