Konig 1998.

Methods	Randomised, placebo‐controlled, double blind
Participants	104 infertile women at risk of severe OHSS (53 HES/51 control) E2 the basic risk factor of OHSS) was > 1500 pg/mL and more than 10 follicles on the day of hCG injection Age (HES 32.6 versus placebo 30.7 years) Duration of infertility (not mentioned) No. of hMG ampoules (not mentioned, similar in both groups ) No. of oocytes (not mentioned, similar in both groups) No. of embryos (not mentioned)
Interventions	Study group: 1000 mL of 6% HES solution shortly after embryo transfer (48 hr after the oocyte retrieval) originally 104 pt randomised: HES 53 control 51; data presented only for 51 and 50 patients respectively. dropout 2.9% (3 women; 2 missing data, 1 allergic reaction) Duration of infusion: over 2 hours Control group: 1000 mL NaCl 0.9% solution
Outcomes	Method of diagnosing severe OHSS: criteria of WHO, 1973 Severe OHSS 0/53 versus 1/51 Pregnancy: not stated but similar between both group Method of diagnosing pregnancy: not stated (clinical pregnancy) Tolerability: yes Safety: one case of urticaria Cost‐benefit: not stated
Notes	Commercially funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number table
Allocation concealment (selection bias)	Unclear risk	Methods not reported
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Double blinded; both patients and physicians blinded, but outcome assessors not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	101/104 (97%) randomised women were included in analysis
Selective reporting (reporting bias)	Unclear risk	Unclear whether data on adverse events were collected prospectively as it was not a prespecified outcome, though mentioned in the results section
Other bias	Unclear risk	No other potential bias identified