Using a Mirror in the Second Stage of Labor: Effects on Duration and Birth Experience: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Using a Mirror in the Second Stage of Labor: Effects on Duration and Birth Experience (NCT06648161), a randomized na study. The primary outcome is Childbirth Experience Questionnaire (CEQ) Total Score.

2. Clinical Question

3. Trial Design

This is a randomized, parallel-group trial with no masking. The registry lists an enrollment of 122 and identifies Kocaeli University as the sponsor. The study status is completed; its listed start date is 2023-02-01 and its primary completion date is 2024-06-30. The registry lists the phase as not applicable.

Participants were assigned to a labor-mirror group or a control group. In the experimental arm, a mirror was used during the second stage so the woman could see her own perineum while pushing. The control arm received routine midwifery care with no intervention. The record does not report further details about sequence generation, allocation concealment, or how assignment was implemented.

The primary outcome was the Childbirth Experience Questionnaire (CEQ) total score, assessed within 24 hours postpartum. The secondary outcome was duration of the second stage of labor, measured in minutes during the birth process. The record also describes an opinion form about mirror use, but posted outcome results for that form are not reported in the registry record.

The posted outcome summaries contain 61 participants in each arm for the CEQ and 61 in each arm for the duration outcome. The primary outcome description says that withdrawals and incomplete questionnaires were excluded; the registry record does not give the number of such exclusions or explain whether the posted analyses follow an intention-to-treat approach. No masking was used, which is relevant when interpreting a self-reported experience measure. The record does not provide further procedural or analytic detail beyond the posted descriptions.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Analysis population for the primary outcome, as defined in the registry: The analysis included women who completed the Childbirth Experience Questionnaire within 24 hours after delivery. Participants who withdrew or had incomplete data were excluded.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Childbirth Experience Questionnaire (CEQ) Total Score, measured over Within 24 hours postpartum.

The primary endpoint is the total score on the Childbirth Experience Questionnaire (CEQ), measured within 24 hours after delivery. The CEQ is described in the registry as a validated measure of women's birth experiences. It includes 22 items across 4 subscales. Item scores are summed and converted to a 1-4 scale, producing a total-score range of 22-88. Higher scores indicate a more positive childbirth experience.

A total score provides a summary measure across multiple aspects of experience rather than focusing on one item alone. It allows the two randomized groups to be compared using a continuous outcome. The posted summaries report a mean and standard deviation for each arm, and the comparison is expressed as a mean difference. In general, a mean describes the group average, while a standard deviation describes the spread of individual scores around that average.

The timing matters to interpretation: the questionnaire was completed within 24 hours postpartum, so the endpoint represents participants' reported experience at that time. The registry describes the analyzed population as women who completed the CEQ; those who withdrew or had incomplete data were excluded. Counts and reasons for missing or incomplete questionnaires are not reported in the registry record. The endpoint therefore describes the posted questionnaire results, rather than necessarily representing every randomized participant's experience.

7. Results Posted in the Registry

• Experiment: mean 73.85 versus 70.22 on control; difference 3.63 (95% CI 0.19 to 7.07), standardized effect d = 0.37; z-test p = 0.038.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Duration of the Second Stage of Labor

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Experiment: mean 12.52 versus 19.48 on control; difference -6.96 (95% CI -8.76 to -5.16), standardized effect d = -1.37; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Experiment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcome concerns duration of the second stage of labor. Its posted group summaries and unadjusted comparison point in the direction of a shorter average duration in the mirror arm. The primary CEQ comparison points toward a higher average childbirth-experience score in that arm. Taken together, the directions are compatible with a pattern in which the mirror arm had a more positive average reported experience and a shorter average second stage. This is a description of the outcomes, not evidence that one result caused the other.

The outcomes capture different constructs. Duration is measured in minutes, whereas CEQ is a participant-reported summary of birth experience. A shorter recorded duration does not necessarily explain a higher experience score, and a higher score does not establish why the average duration differed. The registry record does not report an analysis linking the two measures, or an analysis of whether duration explains any part of the CEQ result.

Secondary results generally carry less weight than a prespecified primary result because they may be less central to the main research question and because examining multiple outcomes can increase the chance of apparently notable results arising by chance. General statistical explanation: when several hypotheses are tested, a collection of unadjusted p-values does not control the overall chance of a false-positive finding. Whether multiplicity adjustments were planned or used is not reported in the registry record. The secondary result should therefore be considered alongside the primary outcome and the missing detail about the analysis plan, rather than treated as independent confirmation of the primary finding.

The registry lists one secondary outcome and no posted analysis records. It does not report whether other exploratory measures were analyzed, whether the secondary outcome was prespecified in the same form, or whether the investigators adjusted for multiple comparisons. The overall pattern is informative as a description of the posted outcomes, but the available record does not establish how much inferential weight the investigators intended to place on the secondary result.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Duration of the Second Stage of Labor

9. Statistical Interpretation

10. Statistical Methods Explained

The outcome measures are continuous: the CEQ total score and duration of the second stage of labor. The registry reports each arm's mean and standard deviation, then gives an unadjusted mean-difference comparison. For an independent parallel-group design, the mean difference summarizes how far apart the two group averages are on the original outcome scale. For CEQ, the difference is expressed in score units; for duration, it is expressed in minutes.

What does the mean difference represent?

The primary comparison uses the control mean as the reference and subtracts it from the experimental-arm mean. A positive CEQ difference therefore indicates a higher average score in the mirror arm, while a negative duration difference indicates a lower average number of minutes in that arm. These signs describe direction, not benefit or harm on their own. Interpretation depends on what the measure represents and the way its scale is oriented. The CEQ description says that higher scores indicate a more positive experience.

A difference in means is a group-level summary. It does not indicate that the same difference occurred for every participant, and it does not show how much the individual score distributions overlap. The standard deviation describes spread among individual observations. It is not the uncertainty around the estimated mean difference. The standard error, in contrast, describes the sampling uncertainty of an estimate and is used when constructing a confidence interval and test statistic.

How should the p-value be read?

The posted p-values are unadjusted. In general, a p-value is calculated under a null model in which there is no group difference and measures how incompatible the observed data are with that model, given the test assumptions. It is not the probability that the null model is true, the probability that results are due to chance, or a measure of the size or importance of an effect. The primary unadjusted p-value is 0.038. The duration comparison has p < 0.001. These values should be interpreted with the estimates and confidence intervals, not in isolation.

The registry record does not report the investigators' complete statistical analysis plan, the exact test used by the sponsor, or any adjustment for covariates. The comparison estimates are recalculated, unadjusted comparisons from the posted summary statistics. No sponsor-reported analysis records are posted. The registry discrepancy flag is false, so the posted recalculations can be described without a reported discrepancy; they should still not be mistaken for a documented adjusted analysis.

Why does variation matter?

General statistical explanation: greater variation among individual observations can make a group mean less precise, all else being equal. Standard deviations describe this variation in the posted groups. They do not indicate whether the outcome is normally distributed, whether there are outliers, or whether the assumptions of a particular test were checked. Individual-level data and diagnostic information are not reported in the registry record.

Over-dispersion is a concern when observed variation exceeds what a chosen statistical model assumes. General explanation: if a model underestimates variation, standard errors can be too small and confidence intervals can be too narrow. The registry record does not report a count model or evidence of over-dispersion, and the posted outcomes are analyzed as continuous measures. There is consequently no basis in the record to claim that over-dispersion was assessed or was a problem in this trial.

What do the confidence intervals add?

General statistical explanation: a confidence interval expresses uncertainty around an estimate and indicates which values are reasonably compatible with the data under the interval's assumptions. A wide interval indicates less precision than a narrow interval. It is not a range that contains a fixed proportion of individual participants' scores, and it is not a guarantee that the true effect lies within its limits. Here, the interval for the CEQ comparison is an unadjusted recalculation from posted summaries. The record does not report the sponsor's own inferential analysis or a model-based adjustment.

Random assignment is intended to support comparisons between groups, but the registry record does not provide enough detail to assess the assignment procedure or adherence to it. The record also does not report masking; it explicitly lists none. Because the CEQ is completed by participants, awareness of group assignment could be relevant to responses. That is a general consideration, not evidence that responses were biased in this trial. The registry record does not report whether investigators evaluated this possibility.

11. Confidence Intervals and Precision

The recalculated unadjusted CEQ mean difference is 3.63 points, with a 95% confidence interval of approximately 0.195 to 7.065 points. The interval is above zero but extends across a range of possible positive differences. This supports describing the posted estimate as favoring a higher average CEQ score in the mirror arm, while also recognizing uncertainty about the size of that difference. The registry does not provide a threshold for a clinically important CEQ difference, so the interval cannot establish whether the observed difference is important to participants.

In general, a confidence interval combines the estimated effect with its sampling uncertainty. Its width is a measure of precision: narrower intervals indicate more precise estimates, while wider intervals leave greater uncertainty about the effect's magnitude. The interval does not describe the range of individual CEQ scores, and it should not be read as a probability statement about the fixed underlying effect. The posted group standard deviations describe the spread of individual scores; the confidence interval instead describes uncertainty in the estimated between-group difference.

The CEQ interval is an unadjusted recalculation from the posted summary statistics, not a sponsor-reported adjusted interval. The registry record lists no sponsor-reported analysis records. Its exact statistical plan, including whether any additional interval estimates were calculated by the investigators, is not reported in the registry record. The displayed precision should therefore be understood in the context of the posted group summaries and the unadjusted comparison, rather than as evidence that all sources of uncertainty have been addressed.

The interval's lower bound is close to zero, and the estimate is not so precise that it identifies one exact magnitude. Precision and statistical significance are related but not identical concepts: a result can have an interval that excludes zero while still allowing uncertainty about the size and importance of an effect. The posted CEQ result should accordingly be interpreted with both its point estimate and interval, alongside the outcome's meaning and the trial's reporting limitations.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed effect, not a report of the trial's original design calculation. For these continuous outcomes, the figures are participants per arm, not total events. The planning assumptions listed in the registry are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. The trial's original sample-size assumptions are not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm needed for an 80% chance of detecting the chosen effect under those assumptions, if that effect is the true one. The 90% power column gives the corresponding planning number for a 90% chance. Power is a design property under specified assumptions; it is not a measure of the probability that a particular result is true. These figures are not observed power.

The planning display considers 100%, 75%, and 50% of the observed effect. For the primary CEQ outcome, planning for 100% of the observed effect gives 112 participants per arm for 80% power and 150 for 90% power. Planning for 75% gives 199 participants per arm for 80% power and 266 for 90% power. Planning for 50% gives 447 participants per arm for 80% power and 598 for 90% power. The pattern illustrates a general design principle: smaller effects are harder to distinguish from random variation, so detecting them requires more participants, all else equal.

Because the illustration uses the observed effect as its starting point, its figures should not be treated as confirmation that the observed effect is the true effect or as evidence that the trial was adequately planned. Observed effects can be uncertain, especially when estimates are imprecise. The registry record does not report the investigators' original target, their design assumptions, or any original power calculation. The displayed planning numbers answer a conditional question about future planning under the listed assumptions, rather than describing what the completed trial was designed to achieve.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 3.630; pooled standard deviation σ = 9.680.
2. n = 2 × (1.96 + 0.842)² × 9.680² / 3.630² = 111.6, rounded up to 112 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 3.63                      # observed difference in means
sigma <- 9.68033057286785                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(6648161)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 112 (80% power), 150 (90% power)
 75% of observed effect: n per arm = 199 (80% power), 266 (90% power)
 50% of observed effect: n per arm = 447 (80% power), 598 (90% power)
power.t.test: 112.6 
Simulated power at n = 112 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists the CEQ total score as the primary outcome and duration of the second stage of labor as a secondary outcome. It also lists two outcome measures. The record does not report a multiplicity strategy, such as a hierarchy of hypotheses or an adjustment to account for testing more than one outcome. It is therefore not possible to determine from the registry record whether the reported unadjusted p-values were part of a broader prespecified testing plan.

General statistical explanation: testing multiple outcomes can increase the chance that at least one result appears unusual under a collection of null hypotheses. This does not mean that a secondary finding is necessarily false; it means that interpretation depends partly on how many analyses were planned and how the results were selected and interpreted. Without a reported multiplicity plan, the secondary result is appropriately read more cautiously than a clearly prespecified primary comparison. The registry record does not report whether any adjustment was conducted outside the posted results.

The primary outcome population is described as women who completed the CEQ within 24 hours postpartum, with participants who withdrew or had incomplete data excluded. The number excluded, the reasons for incomplete data, and the amount of missingness by arm are not reported in the registry record. The record does not describe imputation, sensitivity analyses for missing data, or whether the posted analysis followed intention-to-treat, per-protocol, or another analysis population. The corresponding information for the duration outcome is also not reported in the registry record.

Missingness can affect interpretation if the people with unavailable outcomes differ systematically from those with recorded outcomes. General explanation: excluding incomplete records may yield a biased comparison when the chance of having an outcome recorded is related to the outcome or to group assignment. The available record does not show whether that occurred here, so no direction or magnitude of any potential bias can be inferred.

The registry reports no analysis records. It does not provide the full statistical analysis plan, a description of interim analyses, or details of covariate adjustment. Those features should not be inferred from the randomized design or from the posted summary statistics. As a result, the outcome estimates can be described as unadjusted recalculations, but the broader analysis decisions and their relationship to the original plan remain unclear.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry's serious adverse event figures report zero affected participants in the experimental arm and zero in the control arm. The figures also report zero participants affected by other adverse events in each arm, and zero deaths in each arm. These are the posted counts; they do not establish that no adverse events of any kind occurred outside the events captured or reported in the registry.

In general, an adverse-event count depends on how events are defined, collected, monitored, and submitted. A zero count in a posted summary is not proof that an intervention has no risks. It describes the recorded events in the registry and should be read in light of the available follow-up and reporting details. The registry record does not report further information about event definitions, surveillance procedures, timing of safety collection, or the handling of events not classified as serious.

The record identifies 61 participants at risk for serious events and 61 at risk for other events in each arm. No serious adverse event terms are listed. Safety interpretation should remain limited to these reported counts; the record does not provide detail with which to assess the completeness of ascertainment or to compare particular types of events.

16. What the Result Does, and Does Not, Mean

The posted results describe group averages in a randomized comparison of labor-mirror use with routine midwifery care. The CEQ estimate is in the direction of a higher average reported childbirth-experience score in the mirror arm, and the duration result is in the direction of a shorter average second stage. The CEQ confidence interval and unadjusted p-value quantify statistical uncertainty under the recalculation assumptions, but do not determine whether a difference is important to participants.

These results do not establish that every woman using a mirror would report a more positive experience, or that an individual birth would have a shorter second stage. The means summarize groups; individual experiences and durations can vary. Nor do the two outcomes show that any difference in duration accounts for the CEQ comparison. The registry record does not report a mediation analysis or a direct analysis connecting the outcomes.

The study's randomized allocation is relevant to comparing groups, but the record gives limited detail about the conduct of randomization and no masking. The primary outcome is self-reported, and knowledge of group assignment may be relevant when interpreting reported experience. That is a general consideration rather than evidence that the reported scores were biased. The posted primary outcome population excludes withdrawals and incomplete questionnaires, while details about missingness are not reported.

Statistical evidence is not the same as clinical importance. The registry record does not give a threshold for a meaningful CEQ difference, a target duration difference, or an interpretation of the results by the investigators. The estimates should therefore be read as descriptions of the posted data, with uncertainty, rather than as definitive judgments about the value of mirror use. They also do not establish how results would generalize to settings or populations not represented in the record.

The safety summary reports no serious adverse events, other adverse events, or deaths in either group. Those zero counts should be interpreted as registry-reported counts, not as proof of no possible risk. The record's limited safety detail means that the counts alone cannot answer broader questions about event monitoring or the completeness of reporting.

17. Why This Trial Matters Statistically

This trial is statistically useful because it places two different kinds of outcome side by side: a participant-reported measure of childbirth experience and a measure of time during the birth process. Looking at both can describe more than one aspect of the question, while also making clear that the outcomes are not interchangeable. A change in one does not automatically explain a change in the other.

The primary CEQ comparison illustrates why an effect estimate, confidence interval, and p-value should be read together. The mean difference describes the direction and scale of the group-average contrast, the interval conveys uncertainty about its magnitude, and the p-value summarizes compatibility with a null comparison under the test assumptions. None of these alone tells whether the difference matters to participants. The registry record does not report a threshold for a clinically important score difference, so the statistical result cannot by itself answer that question.

The trial also provides a concrete setting for interpreting unadjusted results. The record lists a primary and a secondary outcome, but does not report a multiplicity strategy or the full statistical analysis plan. That makes it important to distinguish the primary result from secondary evidence and to avoid treating multiple outcomes as independent confirmation without knowing how testing was planned.

Finally, the planning illustration demonstrates how assumptions about the effect to be detected influence the required sample size. Smaller target effects require more participants under the same planning framework. These figures are not evidence about the original design or observed power; the registry does not report the investigators' original sample-size assumptions. This distinction matters when readers assess what a completed trial can say about effects smaller than the observed estimate.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several trial-specific limits affect interpretation. The study was unmasked, and the primary endpoint was a participant-reported questionnaire completed within 24 hours postpartum. In general, a participant's awareness of an intervention can influence responses to a self-reported measure. The registry record does not show whether this occurred or describe any procedure intended to address it.

The primary analysis population excludes participants who withdrew or had incomplete questionnaire data, but the number excluded and reasons are not reported in the registry record. Missing-data methods and sensitivity analyses are also not reported. This limits assessment of whether the posted CEQ comparison represents all randomized participants or whether incomplete data could have affected the group estimates.

The registry provides group summaries and unadjusted recalculated comparisons but no sponsor-reported analysis records. The full statistical analysis plan, any adjustment for baseline characteristics, the exact testing procedure, and a multiplicity approach are not reported in the registry record. The posted comparisons should not be assumed to be adjusted or to reflect every analysis undertaken by the investigators.

The primary outcome is a composite total across 22 items and 4 subscales, but the registry does not post subscale results or item-level information. The record also does not provide a clinically important difference threshold for the CEQ. As a result, the average score contrast cannot be translated from the registry information alone into a judgment about practical importance or which aspects of experience may account for the total-score pattern.

The record identifies Kocaeli University as sponsor and lists a completed study, but does not report further details about recruitment setting, participant characteristics, adherence to mirror use, or protocol deviations. It also does not report results for the opinion form described in the brief summary. These gaps restrict evaluation of generalizability, intervention implementation, and the completeness of the outcome picture.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Using a Mirror in the Second Stage of Labor: Effects on Duration and Birth Experience — NCT06648161.
• Registry record last updated 2025-09-09; status last verified 2025-08.
• Results first posted 2025-08-19.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

The registry record for NCT06648161 describes a completed, randomized, parallel-group trial sponsored by Kocaeli University. It compares use of a labor mirror during the second stage of labor with routine midwifery care and no intervention. The listed enrollment is 122, and masking is listed as none. The study start date is 2023-02-01 and the primary completion date is 2024-06-30.

The primary outcome is the CEQ total score within 24 hours postpartum; the secondary outcome is duration of the second stage of labor. Posted results include group means and standard deviations and unadjusted comparisons. No sponsor-reported analysis records are posted. The primary outcome description excludes withdrawals and incomplete questionnaires, but the number and handling of missing outcomes are not reported in the registry record.

The registry's safety summary reports zero serious adverse events, zero other adverse events, and zero deaths in each arm. The record does not report the original sample-size assumptions, a multiplicity strategy, or a full statistical analysis plan. Its posted outcome estimates should therefore be read as descriptive unadjusted comparisons with the stated uncertainty and reporting limitations.