Lateral episiotomy or no episiotomy in vacuum assisted delivery in nulliparous women (EVA): multicentre, open label, randomised controlled trial.
Bergendahl S, Jonsson M, Hesselman S, Ankarcrona V, Leijonhufvud Å, Wihlbäck AC, Wallström T, Rydström E, Friberg H, Kopp Kallner H, Brismar Wendel S
- DOI
- 10.1136/bmj-2023-079014
- Record issued
- 2026-08-16
- Engine
- 7.39.0
- Exported
- 2026-09-20
Prepared by Alpha1. This document is confidential: it is intended for the recipient it was shared with and must not be redistributed. The live record at alpha1science.com/verify/164e6ba5-30e5-4e83-995a-c41762b6d664 is authoritative.
How this rating was calculated
- IntegrityIntegrity concern−0.5★
- ClaimsEfficacy rests on an unvalidated surrogate endpoint−0.5★
- ReportingData & code availability partially met−0.25★
- No data or code availability links were detected to verify.
- 01Efficacy rests on an unvalidated surrogate endpoint
The primary outcome is obstetric anal sphincter injury (OASI), a clinical diagnosis of a third or fourth degree perineal tear. While OASI is a clinically meaningful outcome, it is a surrogate for long-term functional outcomes such as anal incontinence and quality of life. The paper does not provide evidence linking OASI to these patient-important outcomes, nor does it demonstrate target engagement for the intervention (episiotomy) beyond the procedure itself. The efficacy claim is based on a surrogate outcome without a validated link to the clinical outcome of interest.
“The primary outcome was obstetric anal sphincter injury, defined as a third or fourth degree perineal injury involving the external or internal anal sphincter muscles, or both, as defined by the diagnoses O702 and O703, requiring surgical repair, in the…”
This Kaimen Rigor review uses Kaimen Rigor reviewers trained on a curated corpus of high-fidelity and retracted papers, with expert supervision and curation. It can still make mistakes; verify each finding against the source before relying on it.
This is a well-conducted and transparently reported randomised controlled trial with a clear scientific premise, rigorous design, and appropriate statistical analysis. The main weakness is the vague data availability statement, which lacks a concrete access mechanism for the data. Minor copyedit issues (e.g., a typo in a BMI range and an incomplete sentence) do not affect the scientific integrity.
Both reviewers independently scored all eight dimensions and agreed on every status; no divergence required reconciliation. The study is an interventional RCT; animal-related and cell-line criteria were not applicable. The statistics verification recomputed only 1 test (the primary chi-square) and found it consistent; other reported statistics were not machine-verified and should not be assumed correct. Citation check found no retracted or unresolved references.
Numerical inconsistencies
1 finding · worst lowValues that contradict each other or are impossible for the stated sample: recomputed p-values and test statistics, GRIM/GRIMMER checks on summary numbers, percentages against their own counts, totals against their parts, and estimates against their own confidence intervals.
- Internal contradictions in the reported numbersAssessed
Recomputed 1 test: 1 consistent, 0 inconsistent; 1 via agent-written checks.
- CONSISTENTreported p = .002 · recomputed p = .002Reviewers 1, 2Primary outcome chi-square test for OASI by group
“In the intervention group, 21 (6%) of 344 women sustained obstetric anal sphincter injury, compared with 47 (13%) of 358 women in the comparison group (P=0.002).”
Taken as given: The numbers 21 and 47 are the event counts in the lateral episiotomy and no episiotomy groups, respectively.; The denominators are 344 and 358, respectively.; The test is a two-sided chi-square test without continuity correction.Method: Pearson's chi-square test for 2x2 table using cell counts (21, 323, 47, 311).How we recomputed it: pChi2x2(21, 323, 47, 311)
- lowinternal contradictionTable 1 BMI category '30.0-4.9' appears to be a typo for '30.0-34.9'.
30.0-4.9
Table 1reviewer’s wording
Overstated conclusions
1 finding · worst highConclusions that reach past what the paper's own results support — including a significance claim that no longer holds when the statistic is recomputed, and efficacy resting on an unvalidated surrogate endpoint.
- Efficacy rests on an unvalidated surrogate endpointAssessed
3 major claims checked against the paper's own evidence: all adequately supported.
- supportedReviewers 1, 2Lateral episiotomy reduces the risk of obstetric anal sphincter injury in nulliparous women requiring vacuum extraction.The primary outcome shows a statistically significant reduction with a risk ratio of 0.46 (96% CI 0.28 to 0.78), supporting the claim.Evidence: Primary outcome: 21/344 (6%) vs 47/358 (13%), P=0.002, risk difference -7.0% (96% CI -11.7% to -2.5%).
“Lateral episiotomy can be recommended for nulliparous women requiring vacuum extraction to significantly reduce the risk of obstetric anal sphincter injury.”
AbstractFind in source - supportedReviewers 1, 2No significant differences were noted in postpartum pain, blood loss, neonatal outcomes, or total adverse events.The paper reports no statistically significant differences for these outcomes, consistent with the claim.Evidence: Table 3 and Table 4 show non-significant p-values for these outcomes.
“No significant differences were noted between groups in postpartum pain, blood loss, neonatal outcomes, or total adverse events”
AbstractFind in source - supportedReviewers 1, 2The intervention group had more wound infections and dehiscence.The paper reports significantly higher rates of wound infection and dehiscence in the intervention group.Evidence: Table 4: wound infection 32 (9%) vs 17 (5%), P=0.02; wound dehiscence 32 (9%) vs 12 (3%), P=0.001.
“but the intervention group had more wound infections and dehiscence.”
AbstractFind in source
Premise concern: surrogate not validated for clinical benefit.
- INADEQUATESurrogate endpointThe primary outcome is obstetric anal sphincter injury (OASI), a clinical diagnosis of a third or fourth degree perineal tear. While OASI is a clinically meaningful outcome, it is a surrogate for long-term functional outcomes such as anal incontinence and quality of life. The paper does not provide evidence linking OASI to these patient-important outcomes, nor does it demonstrate target engagement for the intervention (episiotomy) beyond the procedure itself. The efficacy claim is based on a surrogate outcome without a validated link to the clinical outcome of interest.
“The primary outcome was obstetric anal sphincter injury, defined as a third or fourth degree perineal injury involving the external or internal anal sphincter muscles, or both, as defined by the diagnoses O702 and O703, requiring surgical repair, in the Swedish version of the International Classification of Diseases 10th edition. Obstetric anal sphincter injury was the primary outcome in the published meta-analyses, and carries well known risks of both short and long term pelvic floor sequelae.”
- ADEQUATEEffect sizeThe effect size is reported as a risk ratio of 0.46 (96% CI 0.28 to 0.78) for OASI, corresponding to a risk difference of -7.0% (96% CI -11.7% to -2.5%). This represents a more than 50% relative reduction in OASI, which is clinically meaningful given the serious consequences of OASI. The number needed to treat is 14.3, indicating that about 14 women need to receive episiotomy to prevent one OASI. The effect is statistically significant and anchored to a clinically important outcome.
“Obstetric anal sphincter injury occurred in 21 (6%) of the women allocated to lateral episiotomy and in 47 (13%) of the women allocated to no episiotomy (P=0.002), with a risk difference of −7.0% (96% CI −11.7% to −2.5%) and risk ratio of 0.46 (96% CI 0.28 to 0.78).”
Data authenticity concerns
None foundAn adversarial read for patterns associated with data that may not be genuine: results that look too clean, implausibly large effects, duplicated data or images, and methods that do not match the results reported.
Checked — nothing surfaced.
Reporting gaps
1 finding · worst mediumRequired detail the manuscript never states — study design, biological variables, ethics approval and consent, key resources, statistical reporting, data and code availability, and overall transparency.
- Data/code availability incompleteAssessed
The introduction cites a Cochrane review, a 2022 meta-analysis, and observational studies, acknowledging conflicting results and the lack of adequately sized RCTs. The rationale links the uncertainty to the need for a trial, and the hypothesis follows logically. Limitations of prior observational studies (lack of standardisation, confounding) are explicitly discussed.
“A Cochrane review of randomised controlled trials has concluded that routine episiotomy may increase the risk of obstetric anal sphincter injury in non-instrumental birth, while lateral or mediolateral episiotomy might prevent obstetric anal sphincter injury in vacuum extraction in nulliparous women, based on results from pooled observational studies.”
“To date, no adequately sized randomised controlled trial on the protective effect of episiotomy on obstetric anal sphincter injury in vacuum extraction has been published.”
“Observational studies come with limitations. For instance, the differences in effect can be due to lack of standardisation regarding the type of episiotomy, where the angle and incision point have been deemed the most important traits.”
“A Cochrane review of randomised controlled trials has concluded that routine episiotomy may increase the risk of obstetric anal sphincter injury in non-instrumental birth, while lateral or mediolateral episiotomy might prevent obstetric anal sphincter injury in vacuum extraction in nulliparous women, based on results from pooled observational studies.”
“To date, no adequately sized randomised controlled trial on the protective effect of episiotomy on obstetric anal sphincter injury in vacuum extraction has been published.”
“Observational studies come with limitations. For instance, the differences in effect can be due to lack of standardisation regarding the type of episiotomy, where the angle and incision point have been deemed the most important traits.”
Randomization used computer-generated permuted blocks stratified by site, with allocation concealment via sealed opaque envelopes. Blinding was not possible (open-label) but this is stated with rationale. A priori power analysis is reported, though the sample size was revised during the trial. Inclusion/exclusion criteria are pre-specified. The modified intention-to-treat population is defined and justified. Outlier handling is addressed through the definition of analysis populations and missing data handling.
“The randomisation sequence was produced by Karolinska Trial Alliance using computer-based random permuted blocks of two to eight stratified by site.”
“No masking was possible.”
“We used mean rate of obstetric anal sphincter injury in vacuum extraction in Sweden in 2015, according to the Swedish medical birth register, to hypothesise that a 50% reduction of obstetric anal sphincter injury from 12.4% to 6.2% could be detected with 80% power and a P<0.05 with 344 women in each group using a two sided χ 2 test.”
“The randomisation sequence was produced by Karolinska Trial Alliance using computer-based random permuted blocks of two to eight stratified by site. The allocation was done at a 1:1 ratio using consecutive opaque sealed envelopes to facilitate inclusion in medically urgent situations.”
“We used mean rate of obstetric anal sphincter injury in vacuum extraction in Sweden in 2015, according to the Swedish medical birth register, to hypothesise that a 50% reduction of obstetric anal sphincter injury from 12.4% to 6.2% could be detected with 80% power and a P<0.05 with 344 women in each group using a two sided χ 2 test.”
“No masking was possible.”
The paper reports maternal age, BMI, height, country of birth, education, and pregnancy complications in Table 1. Sex is inherently female (nulliparous women), and the paper notes 'Women here refers to people of female sex.' Age and health status are reported. Demographics are comprehensive.
“Women here refers to people of female sex.”
“Age (years), median (range) | 31 (19-43) | 31 (21-47)”
“Age (years), median (range) | 31 (19-43) | 31 (21-47)”
“Inclusion criteria were nulliparous women with a singleton, live, cephalic presenting fetus at 34 gestational weeks or more, requiring vacuum extraction.”
The trial was approved by the Regional Ethical Review Board of Stockholm with a protocol number and amendments. Informed written and oral consent was obtained. Regulatory compliance is implied through adherence to ethical standards, though not explicitly named as a framework.
“The trial was approved by the regional ethical review board of Stockholm before the start (2015/1238-31/2)”
“Informed written and oral consent was obtained by attending midwives or physicians after gestational week 18”
“The trial was approved by the regional ethical review board of Stockholm before the start (2015/1238-31/2) with amendments to approve additional participating hospitals (2017/1005-32, 2018/775-32, 2018/2291-32, 2019-02758, 2019-02758, and 2019-04427)”
“Informed written and oral consent was obtained by attending midwives or physicians after gestational week 18, including during labour if the woman had adequate pain relief and time to reflect, based on the healthcare provider’s judgement.”
The intervention is a standardized lateral episiotomy with precise specifications (angle, length, starting point). No drugs or biological reagents are used. Statistical software SAS 9.4 is identified. The trial is scored on the investigational product and software.
“The trial intervention was a standardised lateral episiotomy, beginning 1-3 cm from the posterior fourchette, at a 60° (45-80°) angle from the midline, and 4 cm (3-5 cm) long”
“Analyses were performed by independent, endpoint masked statisticians using SAS 9.4 (SAS Institute Inc, Cary, NC, USA).”
“Analyses were performed by independent, endpoint masked statisticians using SAS 9.4 (SAS Institute Inc, Cary, NC, USA).”
The primary analysis used a two-sided chi-square test, with adjustment for site via mixed-effects Poisson regression. Exact p-values are reported (e.g., P=0.002). Effect sizes with confidence intervals are provided. Statistical software is identified. Data presentation includes per-group n and appropriate measures. Mathematical plausibility checks were not possible for all values, but no inconsistencies were found.
“In the intervention group, 21 (6%) of 344 women sustained obstetric anal sphincter injury, compared with 47 (13%) of 358 women in the comparison group (P=0.002).”
“The risk difference was −7.0% (96% CI −11.7% to −2.5%).”
“Obstetric anal sphincter injury occurred in 21 (6%) of the women allocated to lateral episiotomy and in 47 (13%) of the women allocated to no episiotomy (P=0.002)”
“with a risk difference of −7.0% (96% CI −11.7% to −2.5%) and risk ratio of 0.46 (96% CI 0.28 to 0.78).”
“Analyses were performed by independent, endpoint masked statisticians using SAS 9.4 (SAS Institute Inc, Cary, NC, USA).”
The data availability statement says 'The study protocol and the statistical analysis plan is available with publication as' but does not specify where data can be accessed. It mentions a DOI for the protocol but not for the data. No repository deposit or accession numbers are provided. Code sharing is not applicable as no custom code is mentioned.
“The study protocol and the statistical analysis plan is available with publication as”
“The study protocol and the statistical analysis plan is available with publication as”
Trial registration number is provided. The paper states results are reported according to CONSORT 2010 and TIDieR. Limitations are discussed in detail, including detection bias and non-adherence. Conclusions are proportional, acknowledging the need for long-term outcome data. Funding sources and competing interests are declared.
“Trial registration ClinicalTrials.gov NCT02643108 .”
“Results are reported according to CONSORT 2010 guidelines and TIDieR checklist.”
“A limitation of this trial is that the obstetric anal sphincter injury diagnosis was not masked for the allocation because this was deemed impossible as an episiotomy would be apparent.”
“Trial registration ClinicalTrials.gov NCT02643108 .”
“Results are reported according to CONSORT 2010 guidelines and TIDieR checklist.”
“A limitation of this trial is that the obstetric anal sphincter injury diagnosis was not masked for the allocation because this was deemed impossible as an episiotomy would be apparent.”
Registered (1 ID: ClinicalTrials.gov). Reporting guideline cited: CONSORT.
Broken references and links
None found · partly checkedReferences checked against Crossref, OpenAlex and Retraction Watch for retractions and resolvability, plus declared data and code links probed for whether they resolve to content matching the paper.
Nothing surfaced — but not everything feeding this category ran (missing: data/code link verification), so read this as a partial clean bill.
Checked 39 references by DOI: 34 verified — 5 no DOI (shown, not verified).
- NO DOIAnal sphincter injuries: a systematic review and assessment of medical, social and ethical aspectsNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIPelvic floor educationNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIGreen-top Guideline No. 29. Third- and Fourth-degree Perineal Tears, ManagementNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIPrioritised research areas within the fields of prevention, diagnosis, and treatment of maternal birth injuriesNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
- NO DOIStatistik om graviditeter, förlossningar och nyföddaNo DOI in the reference — shown for manual review; not independently verifiable (not a fabrication signal).
Copyediting
5 minorWording, consistency and formatting errors that need correcting before submission.
No major wording or formatting errors. 5 minor suggestions below.
5 copyedit issues flagged: mostly consistency, clarity, typo.
- MINORtypoAbstract, Results“P=0.002”→ Ensure consistent use of P vs p.Minor inconsistency in capitalization of p-value.
- MINORconsistencyTable 3, footnote“OASI adjusted†”→ Clarify that the adjusted analysis is for site only.The footnote says 'Adjusted for study site' but the table header could be clearer.
- MINORclarityData availability statement“The study protocol and the statistical analysis plan is available with publication as”→ Complete the sentence with the actual location or DOI.The sentence is incomplete.
- MINORconsistencyTable 1, BMI category“30.0-4.9”→ Correct to 30.0-34.9.Likely typo in BMI range.
- MINORclarityData availability statement“The study protocol and the statistical analysis plan is available with publication as”→ Complete the sentence with a link or repository name.Incomplete sentence.
The published work is robust and methodologically sound; an informed reader should weigh the minor data-availability gap and the small copyedit issues, none of which undermine the conclusions. No erratum is warranted for scientific content, but completing the data availability statement and correcting the BMI typo would improve transparency.
- 1.HIGHdata codeComplete the data availability statement in the Data availability section by specifying where de-identified participant data can be accessed (e.g., a repository like Zenodo or a managed access process with conditions) and provide a persistent identifier or contact for data requests.The current statement is incomplete and vague, which undermines transparency and reproducibility for a data-driven clinical trial.
- 2.HIGHdata codeDeposit the statistical analysis plan and full protocol in a public repository with a DOI, and state the DOI in the data availability statement.The protocol and SAP are only mentioned as available 'with publication' without a concrete location, limiting verification of pre-specified analyses.
- 3.MEDIUMcopyeditCorrect the BMI category typo in Table 1 from '30.0-4.9' to '30.0-34.9'.The current range is impossible and could confuse readers or be seen as a data error.
- 4.MEDIUMcopyeditStandardize the capitalization of p-values (e.g., use 'p' consistently) throughout the manuscript, including the Abstract and Results.Inconsistent p-value notation is a minor but avoidable copyedit issue.
- 5.MEDIUMcopyeditClarify the Table 3 footnote for the adjusted OASI analysis to explicitly state that adjustment was for study site only.The current footnote is ambiguous and could be misinterpreted as adjusting for multiple covariates.
- 6.LOWdata codeIf any custom analysis code was used for the mixed-effects Poisson regression, share it in a public repository with version control and link it in the data availability statement.Sharing analysis code enhances reproducibility, though it is not strictly required for this trial.
The star rating is the report’s one-glance summary. Every paper starts at 5★ and loses stars for the concrete problems the review finds — so a rating is never a vague average, it’s a running total you can read line by line under “How this rating was calculated.”
- Reporting — 8 dimensionseach dimension that fully fails−½★
- each dimension partially met−¼★
- Statistics · Integrity · Claimseach serious problem−1★
- each medium problem−½★
- Citationseach retracted or unverifiable reference−¼★
- Copyeditonly when the manuscript needs a full edit−½★
The rating never drops below 1★, and a demonstrable critical failure (an impossible statistic, a proven ethics violation) caps it at 1★ on its own — so the stars can never look healthy when the verdict is CRITICAL.
The rating draws on a panel of agents. Three independent Kaimen Rigor reviewers grade the eight dimensions below across several independent passes (the shown verdict is their majority vote — steadier than any single run), isolate the paper’s major claims and check its own evidence backs them, and flag integrity concerns. Alongside them, a citation agent resolves every reference against Crossref, OpenAlex, and Retraction Watch; a statistics agent recomputes reported tests; and rule-based checks verify that declared data/code links actually resolve. Full text is required — an abstract-only submission is not analyzed.
Graded against NIH, MDAR, ARRIVE 2.0, CONSORT, EQUATOR, and RRID guidelines. A dimension that doesn’t apply to the study type is skipped, never penalized.
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