Shapiro 2016.

Study characteristics
Methods	Post hoc analysis of the results of 2 single‐centre RCTs (Shapiro 2011a and Shapiro 2011b) Conducted: USA Enrolment: July 2007‐July 2010 Power calculation: stated (referred to Shapiro 2011a). However, study was terminated because of differing embryo quality between the 2 groups. Randomisation: performed by random drawing among identical, opaque, unmarked, sealed envelopes Timing of randomisation: after oocyte retrieval Nature of intervention: slow freezing Follow‐up: live birth, birth weight
Participants	The 2 combined RCTs included 259 women (130 freeze‐all, 129 control) Inclusion criteria: First cycle Cycle day 3 FSH < 10 IU/L > 15 antral follicles observed on baseline ultrasound examination Exclusion criteria: genetic testing of embryos was excluded.
Interventions	Intervention: 2pn oocytes were frozen, and entire cohorts of frozen 2pn oocytes were thawed and subsequently cultured to the blastocyst stage. The morphologically best 1 or 2 blastocysts were transferred on the first day on which at least 1 good expanded blastocyst appeared. Supernumerary expanded blastocysts of high quality were cryopreserved. Control: fresh blastocysts transfer
Outcomes	Birth weight
Notes	Funding was not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Drawing randomly among identical, opaque, unmarked, sealed envelopes.
Allocation concealment (selection bias)	Low risk	Drawing randomly among identical, opaque, unmarked, sealed envelopes.
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	Unclear risk	Data were not reported for all women randomised, but per transfer. Dropouts and loss to follow‐up were not accounted for in the analysis. No ITT analysis was performed. Sufficient data available for analysis per woman in meta‐analysis. Ongoing pregnancy was determined at 10 weeks' gestation instead of 12 weeks' gestation.
Selective reporting (reporting bias)	Low risk	All registered outcomes reported. Both studies used for this follow‐up study were registered in a prospective trials register with the trial numbers NCT00963625 and NCT00963079.
Other bias	Unclear risk	Trial was pre‐terminated after interim analysis. Interim analysis was preplanned, but calculated per transfer (unit of analysis error) with a P value of 0.03, overestimating possible effects. Stopping rules for interim analysis (embryo quality) were unclear. (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 FET group vs results after first 2 transfers in fresh group).