Methods	Randomisation schedule provided by National Perinatal Epidemiology Unit, Oxford. A person unconnected to study prepared by consecutively numbered, computer-generated random allocation in sealed opaque envelopes. Methodological qualities: selection bias: low risk; adequate concealment at time of randomisation; performance bias: high risk of bias could have been introduced because researcher cannot be blind to group allocation after randomisation; exclusion bias: moderate risk as, although expected and 2:1 randomisation undertaken, 16 of 40 women in water arm and 2 of 20 in control arm did not receive their allocated treatment. Analysed according to intention to treat. 1 woman withdrew; bias conclusion: moderate risk of bias. Where 1 or more criteria are not met may cause plausible bias that seriously weakens confidence in the results
Participants	2 groups in RCT part of study. Water n = 40. Land n = 20 (2:1 ratio as about local experience was 50% of women choose not to use water) Women recruited through community midwife, posters in clinics, and media promotions and interested women contacted researcher or gave permission to own midwife to pass on information Aged 18-50. Low risk.
Interventions	Women could use pool in first and second stages of labour - results do not distinguish which of the women allocated to pool, did not use pool (16 of 40 women), used pool for first stage only (13 of 40 women), used pool in second stage but not for birth (1 woman), or gave birth in the pool (10 women) (no subgroup analysis) Data entered into both ‘immersion in water versus no immersion during first stage of labour’ AND ‘immersion in water versus no immersion during second stage of labour’ DATA and ANALYSIS section Waterbirth pool - dimensions/volume not described, temperature described as recorded but data not provided No mention of 1-to-1 second care or not.
Outcomes	Intention-to-treat analysis done. Maternal: age, social history, pulse, temperature, maternal satisfaction on scale of 0-6 immediately post birth and in 6 week postal questionnaire Labour: length of first, second stages; analgesia used; augmentation; mode of birth Fetus/neonate: cord arterial and venous gases, Apgar score at 1, 5 and 10 mins, time to first respiration, rectal temperature at birth, ear swabs, method of feeding, date and time of first feed, admission to neonatal unit (plus any interventions needed) infection, any mortality/morbidity Water; duration in water, water temperature, microbiological analysis at end of labour/use
Notes	Non-randomised, preference arm data not included although additional 20 participants in this part of study 16 (40%) of water women did not use water. UK study.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer generated independent of study.
Allocation concealment (selection bias)	Low risk	Consecutively numbered in sealed opaque envelopes.
Blinding (performance bias and detection bias) All outcomes	High risk	High risk of bias could have been introduced because women, carers and researcher cannot be blind to group allocation after randomisation due to the nature of the intervention
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants are accounted for throughout study with no withdrawals
Selective reporting (reporting bias)	Low risk	All outcomes mentioned in method are reported, and seem appropriate for the study and topic
Other bias	Unclear risk	40% or water group did not use water, which is consistent with choice and other papers on this topic

^*prespecified outcomes

CS: caesarean section

FHR: fetal heart rate

KH: Karlskrona Hospital

LH: Lund hospital

NICU: neonatal intensive care unit

OH: Osterund Hospital

OP: occipito posterior

VBAC: vaginal birth after caesarean section