Gaitan 2009.

Study characteristics
Methods	Prospective 2‐armed randomised controlled trial.
Participants	264 women randomised. Inclusion criteria: Pregnant nulliparous women Aged between 20‐35 ≥ 37 weeks' gestation Normal placental function With a medical indication for induction of labour Exclusion criteria: Multiple birth pregnancies Breech position
Interventions	Intervention group: 133 women, X‐ray pelvimetry before their induction according to the Bedoya technique. Control/comparison group: 131 women, not given X‐ray pelvimetry before their induction.
Outcomes	1. Time taken from induction to expulsion or extraction of the fetus 2. Method of extraction (labour or caesarean) 3. Use of instruments during the birth (forceps etc.) 4. Any secondary/adverse effects 5. Perinatal mortality
Notes	Conducted at the unit of clinical management, University Hospital Virgen Macarena in Seville, Spain. Funding source: not stated. Dates study was conducted: unclear Declarations of interest of primary researchers: unclear
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	264 women were chosen in strict chronological order and were distributed into 2 groups according to a random number table.
Allocation concealment (selection bias)	Unclear risk	The random number table was only known by the head researcher in charge of recruitment, the doctor responsible for inductions and the only person who was authorised to take clinical decisions in relation to the use of the X‐ray pelvimetry, which was always evaluated before proceeding with the induction of labour.
Blinding of participants and personnel (performance bias) All outcomes	High risk	"All women who underwent X‐PM were informed of the process in detail and were only included in the study if they gave their consent." Following the induction, the medical staff working during the labour (obstetric surgeons and midwives) were not aware if the woman had undergone X‐ray pelvimetry. Although there was an attempt to blind some staff, women were aware of the pelvimetry. It is likely this blinding could have been broken.
Blinding of outcome assessment (detection bias) All outcomes	High risk	As blinding of staff is not convincing, some outcomes may have been affected by the lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Appears complete.
Selective reporting (reporting bias)	Unclear risk	Not all outcomes are mentioned‐ unclear if this is due to translation.
Other bias	Unclear risk	In text of study it says that 21 caesarean sections were done in each group but the table data shows different, higher numbers.