Study	Mild	Moderate	Severe
Rabau et al (1967)	Grade 1: oestrogen > 150 µg and pregnanediol > 10 mg/24 h Grade 2: + enlarged ovaries and possibly palpable cysts Grades 1 and 2 were not included under the title of mild OHSS	Grade 3: grade 2 + confirmed palpable cysts and distended abdomen Grade 4: grade 3 + vomiting and possibly diarrhoea	Grade 5: grade 4 + ascites and possibly hydrothorax	Grade 6: grade 5 + changes in blood volume, viscosity and coagulation, time
Schenker and Weinstein (1978)	Grade 1: oestrogen > 150 µg/24 h and pregnanediol > 10 mg/24 h Grade 2: grade 1+ enlarged ovaries, sometimes small cysts	Grade 3: grade 2 + abdominal distension Grade 4: grade 3 + nausea, vomiting and/or diarrhoea	Grade 5: grade 4 + large ovarian cysts, ascites and/or hydrothorax	Grade 6: marked haemoconcentration + increased blood viscosity and possibly coagulation abnormalities
Golan et al (1989)	Grade 1: abdominal distension and discomfort Grade 2: grade 1 + nausea, vomiting and/or diarrhoea, enlarged ovaries 5‐12 cm	Grade 3: grade 2 + ultrasound evidence of ascites	Grade 4: grade 3 + clinical evidence of ascites and/or hydrothorax and breathing difficulties	Grade 5: grade 4 + haemoconcentration, increased blood viscosity, coagulation abnormality and diminished renal perfusion
Navot et al (1992)			Severe OHSS: variable enlarged ovary; massive ascites ± hydrothorax; Hct > 45%; WBC > 15 000; oliguria; creatinine 1.0‐1.5; creatinine clearance ≥ 50 mL/min; liver dysfunction; anasarca	Critical OHSS: variable enlarged ovary; tense ascites ± hydrothorax; Hct > 55%; WBC > 25 000; oliguria; creatinine > 1.6; creatinine clearance < 50 mL/min; renal failure; thromboembolic phenomena; ARDS
Rizk and Aboulghar (1999)		Discomfort, pain, nausea, distension, ultrasonic evidence of ascites and enlarged ovaries, normal haematological and biological profiles	Grade A: dyspnoea, oliguria, nausea, vomiting, diarrhoea, abdominal pain, clinical evidence of ascites, marked distension of abdomen or hydrothorax, US showing large ovaries and marked ascites, normal biochemical profile Grade B: grade A plus massive tension ascites, markedly enlarged ovaries, severe dyspnoea and marked oliguria, increased hematocrit, elevated serum creatinine and liver dysfunction	Grade C: complications such as respiratory distress syndrome, renal shut‐down or venous thrombosis