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Table 3 Assessment of the outcome emergency cesarean delivery using adaptation of Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework for assessing the quality of the evidence across studies

From: Abnormal placental cord insertion and adverse pregnancy outcomes: a systematic review and meta-analysis

Profile of individual studies Comments
 Number of studies 4 • References: [6, 14, 18, 19]
 Number of participants 637, 438 • 632, 978 participants are from Ebbing et al. [6]
  Total number of VCI 9566  
  Total number of Abnormal PCI 49,141
  Total number of Normal PCI 578, 731
 Univariable results
  Number of significant effect estimates > 1 3  
  Number of non-significant effect estimates 0  
  Number of significant effect estimates < 1 1 • Reference: [19]
  Not reported 0  
 Multivariable results
  Number of significant effect estimates > 1 2 • Reference: [6, 18]
  Number of non-significant effect estimates 0  
  Number of significant effect estimates < 1 0  
  Not reported 2  
 Risk of diagnostic ascertainment bias
  Very high 0  
  High 0  
  Medium 0  
  Low 4  
Statistical heterogeneity across studies: I 2 = 44% (for abnormal PCI) and I 2 = 74% (for VCI)
 GRADE assessment a Comments
  Phase of investigation Phase 2 (high) • A ‘high’ rating was assigned before applying other GRADE criteria. All studies used cohort designs and sought to confirm the independent association between abnormal PCI with emergency CD.
   GRADE criteria (based on meta-analysis)  
   Study limitations:
    • Downgrade by −1 if most evidence is from studies with moderate or unclear risk of bias for most bias domains (serious limitations).
    • Downgrade by −2 if most evidence is from studies with high risk of bias for almost all bias domains (very serious limitations).
  • All four studies had low risk of diagnostic ascertainment bias.
• No change.
   Inconsistency: unexplained heterogeneity or variability in results across studies
    • Downgrade by −1 when estimates of the risk factor association with the outcome vary in direction (for example, some effects appear protective whereas others show risk) and the confidence intervals show no, or minimal overlap.
  • See Forest plot. There is some heterogeneity in results across studies, (I2 = 44% for abnormal PCI and 74% for VCI).
• The confidence intervals of the four studies overlap with no change in direction noted (the CI of one study included 1 [19]).
• No change.
   Indirectness: the study sample, the prognostic factor, and/or the outcome in the primary studies do not accurately reflect the review question
    • Downgrade by −1 when: (1) the final sample only represents a subset of the population of interest; (2) when the complete breadth of the prognostic factor that is being considered in the review question is not well represented in the available studies; or (3) when the outcome that is being considered in the review question is not broadly represented.
  • No change.
    • Downgrade by −1 if the evidence is generated by a few studies involving a small number of participants and most of the studies provide imprecise results.
  • No change.
   Publication bias:
    • Downgrade by −1 unless the value of the risk/protective factor in predicting the outcome has been repetitively investigated, ideally by phase 2 and 3 studies.
  • No change.
   Moderate/large effect size:
    • Upgrade by +1 if moderate or large similar effect is reported by most studies.
  • Three out of four studies had few events resulting in wide confidence intervals for effect size.
• No change.
   (+, very low; ++, low; +++, moderate; ++++, high)
  1. CD cesarean delivery, PCI placental cord insertion, VCI velamentous cord insertion
  2. aBased on adaptation13 of GRADE evaluation framework