Bloom 2006.

Methods	RCT.
Participants	Nulliparous women from 36 weeks' gestation with a singleton pregnancy and cephalic presentation, in early labour (2‐5 cm cervical dilatation) with ruptured amniotic membranes who gave informed consent.
Interventions	'Open' group: FPO sensor placed and FPO values displayed. 'Masked' group: FPO sensor placed and FPO values not displayed (FPO values recorded on computer). Both groups: standard fetal heart rate monitoring; labour management at the clinician's discretion.
Outcomes	Primary: caesarean section (any indication). Secondary: caesarean section for nonreassuring fetal status or dystocia; "fetal vulnerability index" (stillbirth, neonatal death, 5‐min Apgar score less than 3, umbilical pH less than or equal to 7, seizures, admission to NICU for greater than or equal to 24 hours); other neonatal morbidity.
Notes	Fetal oximetry system used: Nellcor OxiFirst.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	After the fetal oximetry sensor was placed, randomisation was performed by a research nurse using an encrypted computer program.
Allocation concealment (selection bias)	Low risk	After the fetal oximetry sensor was placed, randomisation was performed by a research nurse using an encrypted computer program.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding of intervention: women and clinicians were blinded to FPO values in the 'masked' group: however, they were not actually blinded to intervention. It would not have been feasible to fully blind the clinician or participant, given that FSpO2 values were used for clinical judgement.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Research nurses obtained data from the maternal and infant charts. Adverse maternal outcomes (placental abruption or prolonged fetal heart rate deceleration at the time of sensor placement) and the composite neonatal outcome were further verified by investigators. "Chart reviewers had no knowledge of the randomization assignment" (p2198).
Incomplete outcome data (attrition bias) All outcomes	Low risk	The published protocol noted the aim of recruiting 10,000 women. When 5017 women had been recruited and their outcomes examined at the third interim analysis. the Data Safety and Moniritoring Committee advised that sufficient recruitment had been undertaken to detect the 15% difference in the primary outcome of caesarean section rate with 90% power (as the higher than expected caesarean section rate once the trial was underway). Recruitment ceased once this decision was agreed upon, with a total of 5341 women randomised and their outcomes analysed.
Selective reporting (reporting bias)	Low risk	No evidence of selective reporting.
Other bias	Low risk	No evidence of other bias. The report aligns with the limited details available in the protocol published when the RCT was in progress (see attrition bias).