Abstract: We included a total of 27 trials, and 26 trials involving 15,858 women provided usable outcome data for analysis. These trials were conducted in 17 different countries: 13 trials were conducted in high-income settings; 13 trials in middle-income settings; and no studies in low-income settings. Women allocated to continuous support were more likely to have a spontaneous vaginal birth (average RR 1.08, 95% confidence interval (CI) 1.04 to 1.12; 21 trials, 14,369 women; low-quality evidence) and less likely to report negative ratings of or feelings about their childbirth experience (average RR 0.69, 95% CI 0.59 to 0.79; 11 trials, 11,133 women; low-quality evidence) and to use any intrapartum analgesia (average RR 0.90, 95% CI 0.84 to 0.96; 15 trials, 12,433 women). In addition, their labours were shorter (MD -0.69 hours, 95% CI -1.04 to -0.34; 13 trials, 5429 women; low-quality evidence), they were less likely to have a caesarean birth (average RR 0.75, 95% CI 0.64 to 0.88; 24 trials, 15,347 women; low-quality evidence) or instrumental vaginal birth (RR 0.90, 95% CI 0.85 to 0.96; 19 trials, 14,118 women), regional analgesia (average RR 0.93, 95% CI 0.88 to 0.99; 9 trials, 11,444 women), or a baby with a low five-minute Apgar score (RR 0.62, 95% CI 0.46 to 0.85; 14 trials, 12,615 women). Data from two trials for postpartum depression were not combined due to differences in women, hospitals and care providers included; both trials found fewer women developed depressive symptomatology if they had been supported in birth, although this may have been a chance result in one of the studies (low-quality evidence). There was no apparent impact on other intrapartum interventions, maternal or neonatal complications, such as admission to special care nursery (average RR 0.97, 95% CI 0.76 to 1.25; 7 trials, 8897 women; low-quality evidence), and exclusive or any breastfeeding at any time point (average RR 1.05, 95% CI 0.96 to 1.16; 4 trials, 5584 women; low-quality evidence). Subgroup analyses suggested that continuous support was most effective at reducing caesarean birth, when the provider was present in a doula role, and in settings in which epidural analgesia was not routinely available. Continuous labour support in settings where women were not permitted to have companions of their choosing with them in labour, was associated with greater likelihood of spontaneous vaginal birth and lower likelihood of a caesarean birth. Subgroup analysis of trials conducted in high-income compared with trials in middle-income countries suggests that continuous labour support offers similar benefits to women and babies for most outcomes, with the exception of caesarean birth, where studies from middle-income countries showed a larger reduction in caesarean birth. No conclusions could be drawn about low-income settings, electronic fetal monitoring, the timing of onset of continuous support or model of support. Risk of bias varied in included studies: no study clearly blinded women and personnel; only one study sufficiently blinded outcome assessors. All other domains were of varying degrees of risk of bias. The quality of evidence was downgraded for lack of blinding in studies and other limitations in study designs, inconsistency, or imprecision of effect estimates. Continuous support during labour may improve outcomes for women and infants, including increased spontaneous vaginal birth, shorter duration of labour, and decreased caesarean birth, instrumental vaginal birth, use of any analgesia, use of regional analgesia, low five-minute Apgar score and negative feelings about childbirth experiences. We found no evidence of harms of continuous labour support. Subgroup analyses should be interpreted with caution, and considered as exploratory and hypothesis-generating, but evidence suggests continuous support with certain provider characteristics, in settings where epidural analgesia was not routinely available, in settings where women were not permitted to have companions of their choosing in labour, and in middle-income country settings, may have a favourable impact on outcomes such as caesarean birth. Future research on continuous support during labour could focus on longer-term outcomes (breastfeeding, mother-infant interactions, postpartum depression, self-esteem, difficulty mothering) and include more woman-centred outcomes in low-income settings.

Plain-language summary: We found 26 studies that provided data from 17 countries, involving more than 15,000 women in a wide range of settings and circumstances. The continuous support was provided either by hospital staff (such as nurses or midwives), or women who were not hospital employees and had no personal relationship to the labouring woman (such as doulas or women who were provided with a modest amount of guidance on providing support). In other cases, the support came from companions of the woman's choice from her own network (such as her partner, mother, or friend). Women who received continuous labour support may be more likely to give birth 'spontaneously', i.e. give birth vaginally with neither ventouse nor forceps nor caesarean. In addition, women may be less likely to use pain medications or to have a caesarean birth, and may be more likely to be satisfied and have shorter labours. Postpartum depression could be lower in women who were supported in labour, but we cannot be sure of this due to the studies being difficult to compare (they were in different settings, with different people giving support). The babies of women who received continuous support may be less likely to have low five-minute Apgar scores (the score used when babies’ health and well-being are assessed at birth and shortly afterwards). We did not find any difference in the numbers of babies admitted to special care, and there was no difference found in whether the babies were breastfed at age eight weeks. No adverse effects of support were identified. Overall, the quality of the evidence was all low due to limitations in study design and differences between studies. Continuous support in labour may improve a number of outcomes for both mother and baby, and no adverse outcomes have been identified. Continuous support from a person who is present solely to provide support, is not a member of the woman's own network, is experienced in providing labour support, and has at least a modest amount of training (such as a doula), appears beneficial. In comparison with having no companion during labour, support from a chosen family member or friend appears to increase women's satisfaction with their experience. Future research should explore how continuous support can be best provided in different contexts.