Review question
This protocol for a Systematic Review and Meta-Analysis was developed with support from the PRISMA-P. The report of the review will be held in line with the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [11,12, 13].
The research question for conducting the review was structured according to the mnemonic PEOS (P — Populations: Women aged between 10 and 49 years, in labor; E — Exposure (s): risk factors for hemorrhage in the third stage of labor; O — Outcome: women with hemorrhage during birth and postpartum; S — Study design: observational studies (case-control; cohort). Therefore, studies classified as follows will be included in this review: a) regarding the type of participants, those that address women in labor and birth; b) regarding the exposure, those that address risk factors for postpartum hemorrhage/third period of labor; c) regarding the outcome of interest, women who had hemorrhage during labor; postpartum/third period of labor, survivors or who died from this cause; d) regarding the type of studies, observational studies will be selected, including prospective and retrospective cohort studies, as well as case control [14,15, 16]. Accordingly, the question was defined: What are the risk factors for hemorrhage in the third stage of labor described in the literature from 2000 to 2020?
Search strategy
Databases
As for the planning of electronic searches, the following databases were consulted: Searches Embase, BIREME (Latin American and Caribbean Center for Health Sciences Information), SciELO Brazil (Scientific Electronic Library Online Brazil), PubMed (National Library of Medicine) / MEDLINE (Medical Literature Analysis and Retrieval System Online), Scopus, Web of Science and CINAHL (Cumulative Index of Nursing and Allied Health Literature) will be searched for relevant literature. Due to the characteristics of each database, search strategies were chosen by respecting the specificity of each database.
Controlled descriptors in English, Portuguese and Spanish were used, in the plural and singular possibilities for each descriptor, in addition to recovering their synonyms. To this end, terms indexed in the Medical Subject Headings (MeSH) were retrieved as “MeSH terms” and “All Fields”, also in the Descritores em Ciências da Saúde (DeCS) as descriptors and synonyms. Therefore, the following Search Strategy Medline (Table 01) was established. In addition, the Boolean operators AND and OR were adopted in the search strategies.
Table 1 Search strategy - Medline
Domain
|
Terms
|
(P)
Population
|
- pospartum period
- puerperal
- labor stage, third
- third labor stage
- third labor stages
- 1 OR 2 OR 3 OR 4 OR 5
|
(E)
Exposure
|
- risk factor.mp. or exp risk factors/
- population at risk.mp. or exp risk factors/
- 7 OR 8
|
O
(Outcome)
|
- postpartum hemorrhage
- hemorrhage
- hemorrhages
- hemorrhagic
- bleeding
- 10 OR 11 OR 12 OR 13 OR 14
|
|
6 AND 9 AND 15
|
Eligibility criteria
Full texts of primary studies, written in Portuguese, English or Spanish will be identified and retrieved by screening titles and abstracts.
In addition, two independent researchers will select the articles, reading each of these articles by title, by summary and by the full text, according to the following inclusion criteria: primary scientific articles, published between 2000 and 2020, in English, Portuguese or Spanish that address the Risk Factors for Hemorrhage in the Third Period of Labor in observational analytical studies: cohort studies, case control, available in the selected databases. The following exclusion criteria will be considered: theses, dissertations, editorials, integrative and systematic reviews and qualitative studies.
Process and tool for obtaining data
The collected data will be exported to a reference manager, EndNote. The search results in the databases will be exported to Rayyan®, an electronic tool that allows independent evaluation of studies by reviewers. Through it, studies indexed in more than one database will also be identified, and then duplicate publications will be removed [17]. The titles and abstracts of articles will be analyzed by two reviewers, independently, according to the eligibility criteria.
In order to assess the level of agreement between the reviewers, the Kappa coefficient will be calculated to obtain the proportion of agreement between the researchers, removing those given by chance [18]. The following classification will be adopted: <0.00, poor agreement; 0.00-0.20, slight agreement; 0.21-0.40, reasonable agreement; 0.41-0.60, moderate agreement; 0.61-0.80, substantial agreement; and 0.81-1.00, almost perfect [19].
Articles that do not reach consensus between the two reviewers will be assessed by a third reviewer for inclusion or disposal. The selected articles will be integrated into this SR for full reading and extracting data.
Grading of evidence
The level of evidence identified in the analyzed articles will be classified according to the GRADE [20, 21], a system considered sensitive for grading the quality of evidence. In this system, the quality of evidence is describe in four levels: high, moderate, low and very low. Evidence from randomized clinical trials starts with a high level and evidence from observational studies with a low level.
Data extraction
Only published data will be extracted: article characterization, method design, intervention, outcome, results, statistic test and conclusions. Moreover, a peer-analysis of the extracted data will then be performed. The extracted data will be systematized by creating tables.
Risk of bias assessment
The GRADE criteria will be applied for the risk of bias assessments and will be carried out individually by two independent researchers by using the online tool GRADEpro GDT. The evidence will be classify as high, moderate, low and very low. The main conclusions drawn from the synthesis of the included studies will be given based on the criteria that lower the level of evidence, those being: risk of bias, inconsistency, indirect evidence, inaccuracy and publication bias, a large magnitude of effect, the dose-response gradient and residual confounders. In addition, it will be used, independently, assessed risk of bias by using the Newcastle–Ottawa Scale for evaluating the quality of nonrandomized studies [21,22]. Three factors will be considered to score the quality of included studies: (1) selection, including representativeness of the exposed, selection of the non-exposed, ascertainment of exposure and demonstration that at the start of the study the outcome of interest was not present; (2) comparability, assessed on the basis of study design and analysis, and whether any confounding variables were adjusted for; and (3) outcomes. We will rate the quality of the studies in three levels (good, fair and poor) by awarding stars in each domain following the guidelines.
In this review, based on the adopted classification to assess the quality of the evidence, the risk of bias in observational studies - cohort studies and case control studies will be considered in relation to the limitations identified in the description of the method referring to the design or execution of individual studies. Evidence from observational studies can be elevated by allocation confidentiality, blinding, complete segment, outcome reporting and sufficient information to assess whether there is a risk of bias. For each of these domains, the risk of bias will be assessed and classified as high risk, uncertain and low risk.
In the third stage, after reading the full texts, the data will be systematized for all studies included in the analysis by reconciling the results between the independent researchers.
In order to compile and synthesize the results of the different studies included in the review, tables, charts and figures will be designed to compose the presentation of the results.
Strategy for data synthesis
Narrative synthesis will be made with meta-analysis and will be carried out by using a framework that consists of: 1. Developing a preliminary synthesis of findings of included studies 2. Exploring relationships within and between studies 3. Assessing the robustness of the synthesis. If possible, a statistical meta-analysis will be carried out by using Review Manager software (Revman The Cochrane Collaboration, Oxford, UK). In addition, a random-effect meta-analysis will be used for combining data where appropriate, at certain time points and by the outcome[23].