Siavashani 2018.

Study characteristics
Methods	Randomised double‐blinded, placebo‐controlled trial
Participants	Infertile women with PCOS, aged 18 – 40 years undergoing IVF (N = 40) Inclusion criteria: Candidate for IVF without previous history of IVF Exclusion criteria: Women with metabolic abnormalities including thyroid dysfunction, diabetes or impaired glucose tolerance were excluded from the study
Interventions	1. 200 μg/day chromium picolinate (Nature Made, California, USA) Mean age 33.8 ± 1.9 (N = 20) 2. Placebo (Barij Essence, Kashan, Iran) Mean age 33.3 ± 2.7 (N = 20) Treatment for 8 weeks
Outcomes	Serum high sensitivity C‐reactive protein (hs‐CRP) levels Metabolic profiles The following outcomes were reported in the Results section of the paper but not in Methods... Endometrial thickness Number of oocytes retrieved Number of oocytes fertilised Fertilisation rate Pregnancy rate Number of embryos
Notes	Location: Taleghani Hospital, Tehran, Iran Timeframe: Between February and May 2018 Trial registration number: IRCT20170513033941N Informed consent: Yes Ethical approval: approved by the research ethics committee of Shahid Beheshti Sample size power calculation: yes Funding: This study was supported by a grant from the Vice‐chancellor for Research, Shahid Beheshti University of Medical Sciences, and Tehran, Iran Conflict of interests: Unknown ITT: no Author email: Shahrzad Zadeh Modarres email sharzad.modarres@sbmu.ac.ir, Zatollah Asemi email asemi_r@yahoo.com Emailed authors 30 January 2020 asking whether Siavashani 2016 is part of this trial. Author answered saying that these were different trials Siavashani 2016 is excluded due to wrong population i.e. women with PCOS not intending to become pregnant Pregnancy data have been added to Table 4 as unknown whether it is clinical or biochemical
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “This randomized, double‐blinded, placebo‐controlled trial” Quote: “Randomization was done using computer‐generated random numbers.”
Allocation concealment (selection bias)	Low risk	Quote: "Randomization and allocation process were concealed from both the researchers and participants until the completion of final analyses. Another person, not involved in the trial and unaware of random sequences, assigned the subjects to the numbered bottles of tablets".
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "double‐blinded, placebo‐controlled trial” Quote: “Chromium supplements and placebos were matched in terms of shape, appearance, smell and packaging”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Three dropouts were reported in each intervention group, due to personal reasons". Comment: So, overall 34 participants [infertile women with PCOS candidate for IVF receiving chromium (N = 17) and placebo (N = 17)] completed the study (Figure 1). Using ITT approach, all 40 participants (20 in each group) were included in the final data analysis.
Selective reporting (reporting bias)	Low risk	Has a trial registration number and pregnancy is reported, although this is reported in the Results section (not in Methods); also no definitions of pregnancy, so uncertain whether biochemical or clinical
Other bias	Low risk	No other bias found