Assessment of GRADE
We examined the certainty (quality) of evidence for outcomes using GRADE
approach.15 The certainty of evidence was classified
as four levels: high, moderate, low, and very low. Two reviewers
considered comprehensively five factors (risk of bias, inconsistency,
indirectness, imprecision, and publication bias) to assess the certainty
of evidence for the following outcomes: perineal trauma, episiotomy,
first- and second-degree perineal laceration, severe perineal
laceration, duration of second-stage labor. The evidence could be
downgraded from ’high’ by one level for serious (or by two levels for
very serious) limitations.