Aghahosseini 2017.

Study characteristics
Methods	Multicentre RCT Conducted: in 2 fertility clinics in Teheran, Iran Enrolment: January 2016‐April 2016 Power calculation: stated Randomisation: computer‐generated random numbers in wrapped, unlabeled envelope each holding a unique number Timing randomisation: at day of oocyte retrieval, after retrieval Nature of intervention: blastocyst (day 5) cryopreservation by means of vitrification Follow‐up: LBR after the first ET
Participants	72 women (36 freeze‐all, 36 control) Inclusion criteria: Infertile women (information from manuscript) Women undergoing IVF with their own eggs (information from trials register) women with normal HSG and ultrasound of the uterine cavity (information from trials register) Exclusion criteria were: uterine anomaly or previous uterine surgery, oocyte donation, azoospermia, severe endometriosis, previous chemotherapy or radiotherapy, conditions affecting the reproductive status.
Interventions	In the conventional IVF strategy group, a total of 1 or 2 blastocysts (grade A) were transferred at 5th day. Luteal phase support was carried out for all participants. In the freeze‐all strategy, all embryos were cryopreserved by vitrification and after 2 menstrual cycles, artificial endometrial preparation was performed. A total of 1 or 2 grade A thawed blastocysts were transferred.
Outcomes	Primary outcome was clinical pregnancy, defined as a gestational sac with a live fetus on ultrasound 5 weeks after transfer. Secondary outcomes were not specified in the manuscript.
Notes	Funding was not reported. We requested additional information regarding cumulative data from the authors by email but we did not receive a response.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Authors state that women were randomly allocated using random allocation software, no further information provided.
Allocation concealment (selection bias)	Unclear risk	Authors state that women were randomly allocated using random allocation software, no further information provided.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding of doctors and participants was not possible due to the nature of the intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome assessor blinding was not reported, however primary outcome is not likely to be influenced by lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data were analysed for all randomised women.
Selective reporting (reporting bias)	Unclear risk	Study was registered in a prospective trials register with the trial number: IRCT2016122131508N1. However, the study was registered while recruiting as it is stated in the trials register.
Other bias	Unclear risk	(Cumulative) data per subsequent menstrual or cryo‐transfer cycle not reported (relevant for time‐to‐pregnancy comparison and the related comparison of results after first transfer in frozen group vs results after first 2 transfers in fresh group).