Maternal Position During the First Stage of Labor: A Systematic Review

Abstract & Research

Background
Policy makers and health professionals are progressively using evidence-based rationale to guide their decisions. There has long been controversy regarding which maternal position is more appropriate during the first stage of labor. This problem has been examined often and repeatedly and the optimal recommendation remains unclear.

Methods
This is a systematic review of the effect of maternal position during the first stage of labor. The main question addressed here is: Does encouraging women to adopt an upright position or to ambulate during the first stage of labor reduce the duration of this stage? All randomized controlled trials carried out to assess this effect were taken into consideration in this review. The following electronic databases were accessed to identify studies: MEDLINE, Popline, the Scientific Electronic Library On-line and the Latin American and Caribbean Health Science Information. Citation eligibility was independently assessed by two reviewers. The methodological quality of each trial was also evaluated independently by two reviewers and a trial under consideration was included only when consensus had been attained. Allocation concealment and screening for the occurrence of attrition, performance and detection biases were considered when studies were appraised. The decision whether to perform data pooling was based on the clinical similarity of studies.

Results
The search strategy resulted in 260 citations, of which 18 were assessed in full-text. Nine eligible randomized controlled trials were included in the systematic review. Randomization methods were not fully described in eight studies. The allocation concealment was considered adequate in four studies and unclear in five. The investigators pooled the data from seven studies in which the length of the first stage of labor and results were in favor of the intervention, but the high level of heterogeneity (I2 = 88.4%) impaired the meaning of this finding. The intervention did not affect other outcomes studied (mode of delivery, use of analgesia, labor augmentation and condition of the child at birth).

Conclusion
Adoption of the upright position or ambulation during first stage of labor may be safe, but considering the available evidence and its consistency, it cannot be recommended as an effective intervention to reduce duration of the first stage of labor.

Background
Even before the development of modern obstetrics, controversy existed with respect to maternal position during labor. The horizontal position during the first stage of labor is believed to have been introduced by Mauriceau in the 18^th century to facilitate the care of women and the performance of obstetric maneuvers and procedures [1]. The horizontal position was thus incorporated into Western culture as the standard position during labor. Nevertheless, the standardization of this position for labor was never fully accepted, and more than two centuries ago there were those who advocated the value of not confining women in labor to bed [2]. In fact, in most cultures that have not been influenced by this Western custom, women in labor continue to opt for the upright position or to keep ambulating [1].

Throughout the scientific development of obstetrics, this controversy has been examined several times under different perspectives. From the physiological standpoint, the supine position has been observed to be associated with the compression of abdominal blood vessels and impairment of fetal nutrition and oxygenation [3]. It has also been argued that this position would negatively interfere with uterine contractions [4]. However, upright position during first stage of labor may improve maternal comfort and reduce the need for analgesia [5]. In this context, labor without bed confinement became part of a set of actions involved in promoting the empowerment of women and the humanization of labor. In accordance with these views, an argument was built in favor of the upright position during labor.

On the other hand, over the past twenty years, policy makers, health professionals and even the lay society are progressively using an evidence-based rationale to guide their decisions. A considerable amount of knowledge had already been accumulated on the subject more than twenty years ago, and the remaining facts available today have been acquired over that interval of time. In summary, the purpose of the adoption of an upright position has been the enhancement of uterine contractions and fetal condition, and the promotion of maternal comfort [3-5]. Nevertheless, although the issue has frequently been examined, the optimal alternative remains unclear. For this reason, it was decided to carry out a systematic review with the objective of assessing the effect of adopting the upright position or ambulating during the first stage of labor on selected obstetrical and perinatal outcomes.

Methods
This is a systematic review on the effect of maternal position during the first stage of labor. The main question addressed here is: Does encouraging women to adopt an upright position or to ambulate during the first stage of labor reduce the duration of this stage? All randomized controlled trials comparing upright position or ambulation with any other position were taken into consideration. We defined upright position as the adoption of a not supine position during labor, (i.e. walking, sitting, standing, kneeling, and squatting). The following endpoints were evaluated: need for labor augmentation, mode of delivery, use of analgesia, neonatal condition at birth and maternal comfort and satisfaction.

Studies were identified by performing a search of the following electronic databases: MEDLINE, Popline, the Scientific Electronic Library On-line (SciELO) and the Latin American and Caribbean Health Science Information (LILACS). These databases were searched using the following strategy and keywords: ("labor") AND ("first stage" OR "position" OR "mobility" OR "up right" OR "upright" OR "active phase" OR "latent phase" OR "maximum slope" OR "recumbent" OR "lateral" OR "sitting" OR "standing" OR "ambulation" OR "kneeling" OR "squatting"). This search was not restricted by date or language. In addition, the proceedings of several scientific meetings were hand-checked and reference lists of retrieved publications were screened.

Possible eligibility was assessed independently by two reviewers. Initially, the citations identified were evaluated on the basis of their titles and/or abstracts and full text was retrieved if found to be eligible. All citations considered to be clearly irrelevant were excluded. If the information provided by titles or abstracts was considered insufficient to decide on inclusion or exclusion of the publication, the full-text article was retrieved and evaluated. Studies were assessed independently by two reviewers and decision upon inclusion was based on consensus between the two. Methodological quality assessment took into account the adequacy of allocation concealment. The concealment of allocation was considered adequate (and scored as 'A') when the study under consideration adopted a process in which the person deciding about the inclusion of a participant into a randomized controlled trial did not know the comparison group into which that individual was being allocated. In case allocation concealment was unclear, the score was 'B' (Table 1). The occurrence of attrition, performance and detection bias was screened and the sampling method and the mode of presentation of results were also evaluated.

Data extraction and statistical analysis were performed according to the guidelines recommended in the Cochrane Handbook [6]. The decision whether to perform data pooling was based on the clinical similarity of studies. Whenever an alternative measure of variability was applied, an approximation or a direct algebraic relationship was used to obtain the standard deviation. After data pooling, statistical heterogeneity was identified and evaluated as moderate or high (i.e. more than 40% using the I² statistic) [7]. If heterogeneity was low, a fixed effects model was used for statistical analysis, and if heterogeneity was moderate or high the random effects model was applied. Depending on the heterogeneity level, the standardized mean difference (SMD, low heterogeneity) or the weighted mean difference (WMD, moderate to high heterogeneity) was used. Odds ratios (OR) with 95% confidence intervals (CI's) were calculated. Subgroup analyses according to parity and other characteristics of labor (maximum slope phase and protracted labor) were performed. Analysis was carried out using the Revman software package, version 4.2.8 (The Nordic Cochrane Centre, Rigshospitalet 2003).

Results
The search strategy yielded 260 citations, of which 18 were assessed in full-text. Of these, 9 randomized controlled trials were included in the systematic review, with a total of 2,220 women [2,8-15] (Figure 1). None of the studies excluded from the review were randomized controlled trials [1,16-22] and one referred only to the second stage of labor [23]. Main characteristics of studies included in the review are presented in Table 1. The earliest studies were published in 1978 [2,8] and only two were performed in the last ten years [14,15]. All studies were published in English language and two were carried out in developing countries (India [13] and Brazil [15]). Randomization methods were not fully described in eight studies [2,8-14]. The allocation concealment was considered adequate in four studies [8,10,11,15] and unclear in five others [2,9,12-14]. Only one study described sample size calculation [15]. We did not consider blinding to be feasible and, in fact, blinding was not reported in any study included in this review. After data pooling, the heterogeneity was high in three selected comparisons or outcomes. The results mentioned below and the heterogeneity levels are summarized in Table 2.

Duration of first stage of labor
We pooled the data from seven studies in which the duration of first stage of labor was recorded. A total of 2,166 patients were enrolled in those trials [2,10-15]. Two studies accounted for 78.2% (1,694 patients) of all patients enrolled [10,14]. The reviewers observed performance bias in one of these two studies (reporting on 627 randomized women) [10] because of delayed amniotomy in the study group. Another study included in this section randomized only patients with protracted labor [11]. Despite these observations, results favored intervention (WMD (random) -0.83 hours; 95%CI -1.60 to -0.06) (Figure 2).

Mode of delivery
Eight studies examined the mode of delivery [2,8-11,13-15]. The overall cesarean section rate was 5.5% for the intervention group and 5.6% for the control group. (OR (fixed) 0.98; 95% CI 0.67 to 1.43) (Figure 3).

Use of analgesia
The use of analgesia was assessed in six studies [2,8,10,11,14,15]. A statistically significant result in favor of the treatment group was found in only one study [2]. The overall use of analgesia was high (69.0%). (Pooled data: OR (random) 0.69; 95%CI 0.37 to 1.30) (Figure 4).

Maternal comfort
Three studies examined maternal comfort using different methods [11,12,15]. We judged that data pooling would be inappropriate in this case, as the conversion to a common scale was not feasible. In one study [12], a maternal comfort score developed by the authors themselves was used to evaluate maternal reactions to uterine contractions, including certain behavioral and physiological signs. The overall mean comfort score during the first stage of labor did not differ significantly between the two groups. Another study evaluated women's experiences and the results suggest more women rating their experiences positively in the study group compared to the control group [10]. The third study used a visual-analog scale to evaluate maternal satisfaction during labor [15], resulting in no statistically significant difference between the two groups.

Labor augmentation
Four studies examined the need for labor augmentation [2,8,10,14]. No statistically significant results were observed, but all of them reported what could be a protective effect. (Pooled data: OR (fixed) 0.81; 95%CI 0.65 to 1.01) (Figure 5).

Child condition after birth
Six studies reported 5-minutes' Apgar scores [2,8-11,15]. One study reported a statistically significant difference in favor of the intervention group [2]. (Pooled data: WMD (random) 0.11; 95% CI -0.07 to 0.28) (Figure 6).

Discussion
The main result of this systematic review suggests that encouraging women to adopt an upright position or to ambulate during the first stage of labor reduces its duration. However, the robustness of this finding is limited, since it is associated with a high level of heterogeneity (assessed by the I2). In fact, the consistency of a meta-analysis depends on the similarity of magnitude of the effects of the studies included, and the assessment of the consistency of effects across studies can be carried out by measuring heterogeneity (i.e, the degree of genuine differences between the studies and their results). Considering the 95% confidence interval, this positive effect of maternal position on the duration of labor may be merely marginal.

To critically appraise these results, the presence of any underlying potential sources of heterogeneity has to be examined. Typically, heterogeneity is associated with reporting bias, differences in: the intensity of interventions, the underlying risk, the effect size according to the study sample size and irregularities of data.

Analysis of Figures 2 to 6 may suggest the occurrence of a "small study effect". The small study effect is the trend for smaller studies in a meta-analysis to show larger treatment effects and it is also associated with reporting bias [25]. In this systematic review, two studies accounted for approximately 76% of the total reported sample (large studies) [10,14], two studies accounted for almost 14% of the sample (intermediate studies) [12,15], while five studies, each with fewer than 100 participants, accounted for approximately 10% of the total reported sample (small studies) [2,8,9,11,13]. Using the study performed by Flynn et al [2] as an example of the small study effect, this study accounts for approximately 3% of the total meta-analysis sample, but may have a much greater weight in the analysis (Figure 2). There is some controversy regarding how to deal with the small study effect. Simulation of exclusion of the Flynn study would change the conclusion of this meta-analysis (duration of first stage of labor, WMD (random) = -0.65; 95%CI -1.43-0.13).

Another possible source of heterogeneity in the present meta-analysis is the intensity of intervention in the studies included and the occurrence of several degrees of contamination (provision of the intervention to the control group) and co-intervention (provision of unintended additional care to either comparison group), as noted in Table 1. On the other hand, the occurrence of a performance bias in one of the larger studies was observed [10]. In this study, amniotomy was performed later in the study group. Considering that early amniotomy is associated with a reduction in the duration of first stage of labor [24], it is possible that the delay in performing amniotomy counterbalanced any possible effect of ambulation or standing in the upright position during the first stage of labor in that study.

The adoption of an upright position or walking during labor possible interferes on the performance of other interventions such as amniotomy, analgesia and monitoring during labor. The reverse way of this statement is also valid and this fact makes the isolation of possible effects of upright position or walking during labor a difficult task.

The evaluation of secondary outcomes suggests that the upright maternal position is a safe intervention. At the same time, while it produces no apparent benefit, neither does it appear to do any harm. The effect on maternal comfort is unclear, but freedom of movement may benefit patients individually.

Conclusion
Adoption of the upright position or ambulation during first stage of labor may be safe, but considering the available evidence and its consistency, it cannot be recommended as an effective intervention to reduce duration of the first stage of labor.

Additional well-designed studies are warranted to further clarify the effectiveness of maternal position on the duration of labor and other outcomes.

Competing interests
JPS declares that he has no competing interests. MAM, JGC, MYM are the authors of one of the studies included in the present systematic review.

Authors' contributions
JPS and JGC participated in all the steps of the project, including project development, data extraction, data analysis and writing the final report. JGC, MAM and MYM took the initiative to develop the protocol for this systematic review. JPS and MAM were responsible for implementing the search strategy, the citation eligibility assessment and data extraction. JPS and JGC were responsible for the critical appraisal. All authors provided suggestions for the manuscript, read it carefully, agreed on its content and approved the final version.

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