Study	Reason for exclusion
Bender 1968	Two studies were reported, N = 12 in the first study and N = 30 in the second. Neither was an RCT. Both employed alternate allocation that was neither centrally controlled nor concealed. The researcher delivered the intervention and collected outcome data. In the first study the researcher also enrolled participants. No usable outcome data were reported
Bochain 2000	The intervention was not continuous labour support. It was a short nursing intervention (taking approximately 1 hour) administered in early labour for women undergoing Misoprostol induction
Brown 2007	The intervention was not continuous labour support. It was an educational intervention to promote childbirth companions in hospital deliveries. A cluster‐RCT was undertaken at 10 South African state maternity hospitals
Dalal 2006	Not an RCT. 100 randomly‐selected mothers who had a birth companion were compared with 50 randomly‐selected mothers who did not have one. Mothers were matched for age and socioeconomic status
Dong 2009	Intervention is the effects of air sac combined with nitrous oxide gas and doula care; Not a clean comparison with the control group who have no access to nitrous oxide gas
Gordon 1999	30% of those enrolled were excluded post‐randomisation, 73/232 in the doula group and 69/246 in the control group. A letter was sent to the first author, asking for data on the excluded participants that would permit an intent‐to‐treat analysis. If and when a response is received, we will evaluate the trial report again
Hemminki 1990c	Third study in the same report as Hemminki 1990a and Hemminki 1990b. This was a small pilot RCT of support by laywomen that was 'stopped for economic and other practical reasons'. 31 women were enrolled but 7 dropped out (all from the intervention group). Very little data were reported and it was not separated by treatment group and thus unusable
ISRCTN33728802	Intervention was midwifery education for either support in labour or evidence‐based care
Lindow 1998	Support was not continuous, and was quite brief in duration. 16 women in active labour were randomised to either 1 hour with a supportive companion or 1 hour without. The only outcome was maternal oxytocin level for 16 minutes post‐support or control period
Manning‐Orenstein 1998	Not a randomised trial. Women chose to either have a doula or have Lamaze preparation for childbirth
Orbach‐Zinger 2012	Intervention is the presence of a partner during epidural insertion, not during labour
Ran 2005	Not an RCT. Translated personal communication from the author stated "I randomly sampling allocated the patient, did not use any random tool"
Riley 2012	Published in abstract form ‐ authors contacted but unable to provide additional information
Scott 1999	Not a trial. A review of selected studies of intrapartum support
Senanayake 2013	Control group not randomised
Sosa 1980	Strong evidence of selection bias. "A woman was removed from the study if labour was false or prolonged; if fetal distress necessitated an intervention such as oxytocin, caesarean delivery, or forceps"; or if the infant was asphyxiated or ill at birth, etc. "If a woman was removed, her group assignment was inserted at random into the pool of unused assignments. Women were enrolled in the study until there were 20 in the control group and 20 in the experimental group." The total study sample of 127 mothers includes 95 in the control group and 32 in the experimental group. Thus assignment was not random
Trueba 2000	Direct contact with investigator revealed that randomisation was not used. On arrival at the hospital, women were asked if they wanted to have a doula. If they accepted, a doula was assigned to them. Also support was not continuous throughout active labour for most women, since admission to the labour ward (and assignment of a doula) did not usually occur until 8 cm
Tryon 1966	Not an RCT. "After a random start, the matched groups were alternately assigned to experimental and control groups." Women who developed severe complications in labour (number not specified), such as fetal distress, were dropped from the study
U1111‐1175‐8408	Intervention is an educational booklet for birth companions, not continuous support
Wan 2011	The study compared 2 types of nursing care: intervention is continuous primary nursing care, compared to task‐centred primary nursing care
Zhang 1996b	Not a trial of continuous 1‐to‐1 support. On admission to the labour ward, women received instruction about normal labour, non‐pharmacological methods to ease pain, and how to push in second stage, from a team of physicians and nurses. Support was continuous, depending on the women's needs, but not 1‐to‐1

EFM: electronic fetal monitoring
 RCT: randomised controlled trial