The Comparative Effectiveness of Liberal Versus Restricted Maternal Administration of Oxygen During Labor: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Comparative Effectiveness of Liberal Versus Restricted Maternal Administration of Oxygen During Labor (NCT02752490), a non-randomized na study. The primary outcome is Number of Participants Who Delivered by Cesarean.

2. Clinical Question

The study objective also described fetal acidemia at birth as an outcome of interest. Secondary outcomes listed in the record include umbilical artery pH < 7.10, cesarean delivery for non-reassuring fetal status, a low Apgar score at 5 minutes, neonatal intensive care unit admission, duration of maternal oxygen use, other intrauterine resuscitation, and clinical chorioamnionitis. These outcomes cover delivery, newborn status, and care during labor, but their results are not reported in the registry record.

The question is comparative, but the design was not randomized. The arms therefore should not be read as if participants had been assigned by chance to otherwise interchangeable groups. The record supports describing the strategies and the intended question; it does not establish that any difference in outcomes was caused by oxygen policy.

3. Trial Design

The registry describes a controlled before-and-after study with nonrandomized allocation and a parallel model. The study status is completed, and the recorded enrollment is 844. The primary completion date is 2016-07-31, and the recorded study start is 2016-04. The sponsor is The University of Texas Health Science Center, Houston. Phase is recorded as NA, and masking is listed as none.

The two strategies were liberal use and indicated use of maternal oxygen during labor. For liberal use, oxygen could be given when any category 2 tracing was present, at the discretion of the primary nurse or physician. For indicated use, oxygen was reserved for selected category 2 tracing circumstances, including recurrent late fetal heart rate decelerations, prolonged fetal deceleration, and fetal tachycardia. The registry’s description of that arm is incomplete, so its full criteria cannot be reconstructed from the record.

Because allocation was nonrandomized, the comparison may reflect differences between the groups beyond the oxygen strategy. In a before-and-after design, changes over time in care or patient mix can also complicate interpretation. The record does not report the timing of the comparison periods, how participants entered each arm, or whether other aspects of care changed between periods. Those details matter for judging how comparable the groups were.

The record identifies the primary outcome as the number of participants who delivered by cesarean, measured at birth. It also lists secondary outcomes and adverse-event information. Although the study is marked completed, the primary and secondary outcome results are not reported in the registry record. Completion status alone does not indicate what the results were or whether the intended comparison was conclusive.

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

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 Number of Participants Who Delivered by Cesarean, measured over at time of birth.

The primary endpoint is the number of participants who delivered by cesarean, assessed at the time of birth. It is a count of participants experiencing the delivery outcome, not a measure of the duration or severity of labor. The study objective frames this endpoint as a way to compare the two oxygen-use strategies.

Cesarean delivery is clinically and operationally relevant to a labor-management study because it captures a major delivery outcome. However, the endpoint alone does not identify why a cesarean occurred. The registry separately lists cesarean delivery for non-reassuring fetal status as a secondary outcome, distinguishing that stated reason from the broader primary count.

To interpret a comparison, readers would need outcome counts for each arm and an analysis that accounts for the study design. Those results and an effect estimate are not reported in the registry record. Therefore, the endpoint definition clarifies what was intended to be measured, but it does not establish whether the outcome differed between strategies or how precisely any difference was estimated.

In general, a confidence interval around an effect estimate communicates the range of values compatible with the data under the analysis assumptions. It helps distinguish a precise estimate from one with substantial uncertainty. No confidence interval for this primary endpoint is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Interpreting this study requires separating the registered design, the outcome definitions, and any statistical results. The record supplies design details and an endpoint definition, but does not report primary outcome results or analyses. The following statistical concepts are general explanations; they do not imply that a particular analysis was performed in this study.

What does nonrandomized allocation mean?

In a randomized trial, assignment by chance is intended to balance measured and unmeasured characteristics between groups, on average. That protection is not available in the same way when allocation is nonrandomized. The registry lists allocation as nonrandomized and describes the study as controlled before-and-after. As a result, the groups may differ in characteristics related to cesarean delivery, and such differences can complicate an unadjusted comparison.

General statistical approaches for nonrandomized comparisons may adjust for measured characteristics, but adjustment cannot automatically remove confounding from unmeasured factors or poorly measured variables. A valid interpretation also depends on how participants were selected, how the periods were defined, and whether other care practices changed. These details and any adjustment strategy are not reported in the registry record.

What would the primary outcome analysis require?

The primary outcome is a participant count for cesarean delivery at birth. An analysis could compare the groups using outcome counts and an appropriate effect measure, but the choice of measure and model should reflect the design and data structure. For an interpretable result, readers would ordinarily look for the outcome count in each group, the denominator used for each group, the estimated contrast, its uncertainty, and the analysis method. These are not reported for the primary endpoint in the registry record.

In general, a confidence interval expresses uncertainty around an estimated effect under the assumptions of the chosen analysis. A narrow interval indicates greater precision than a wide interval, but precision does not resolve bias from nonrandomized allocation. A statistical test addresses compatibility with a null model under its assumptions; a test result alone does not describe clinical importance or eliminate confounding. No primary-outcome confidence interval or test result is reported.

How should planning illustrations be read?

The statistical planning assumptions describe illustrations based on the observed effect, rather than the trial’s own design. They use a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. For non-time-to-event outcomes, such illustrations are expressed as participants per arm; time-to-event calculations use a total number of events.

These calculations are planning illustrations, not observed power and not evidence about the study’s outcome. The registry record does not report the trial’s original sample-size justification. The observed effect used as the basis for the illustrations is not reported in the registry record, so readers cannot assess its magnitude or how stable the planning values might be. A planning calculation based on an observed estimate can also inherit uncertainty from that estimate. It should not be interpreted as a prospective design guarantee.

Why can over-dispersion matter?

In general, over-dispersion occurs when variability in the data exceeds what a statistical model assumes. It can make standard errors too small if the model does not account for the extra variability, leading to overly narrow confidence intervals and misleading test results. The primary outcome is described as a count of participants with an event, rather than a repeated count per participant. The registry does not report a model or dispersion parameter, and there is no basis in the record to say that over-dispersion was assessed or relevant to the reported analysis.

What can be inferred from the listed analyses?

The registry lists zero analyses. That does not establish that no analysis was conducted outside the registry; it means the record does not provide analysis entries to evaluate. It also leaves unanswered whether the primary endpoint was analyzed as planned, how missing outcome data were handled, or whether any covariates were included. Statistical interpretation should therefore remain limited to the registered design and outcome definitions, not an assumed analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Liberal Use of Maternal Oxygen", "Indicated Use of Maternal Oxygen")
n      <- c(409, 435)
events <- c(83, 75)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Liberal Use of Maternal Oxygen  409  83  20.3  16.5  24.5  16.7  24.5  16.7  24.5
ARM  Indicated Use of Maternal Oxygen  435  75  17.2  13.8  21.1  14.0  21.1  14.0  21.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists eight outcome measures, including a primary cesarean-delivery outcome and secondary outcomes involving umbilical artery pH, cesarean delivery for non-reassuring fetal status, Apgar score, neonatal intensive care unit admission, maternal oxygen duration, other intrauterine resuscitation, and clinical chorioamnionitis. Multiple outcomes can be informative, but testing or emphasizing many outcomes raises the possibility of chance findings and selective reporting.

In general, a statistical plan may identify one primary endpoint, specify how secondary outcomes will be interpreted, and describe any adjustment for multiple comparisons. The record identifies the primary endpoint but does not report a multiplicity strategy, a prespecified analysis plan, or which outcome analyses were conducted. Zero analyses are listed in the registry. Thus, the record does not show whether outcome testing was adjusted or whether the secondary outcomes were treated as exploratory.

Missing-data handling is also not reported in the registry record. There is no description of missing endpoint values, exclusions, or how any incomplete observations were handled. The record does not identify analysis populations, such as whether all enrolled participants or a defined subset contributed to the primary outcome analysis. The enrollment figure should not be assumed to be the denominator in every outcome analysis.

These omissions matter because missingness and analysis-population decisions can affect both estimated effects and their uncertainty. In general, an analysis based only on participants with observed outcomes can be biased if outcome availability is related to group assignment or the outcome itself. Without the numbers analyzed, missingness information, and analysis rules, readers cannot determine whether such concerns apply or how sensitive results would be to alternative assumptions.

The absence of these details does not prove that multiplicity, missing data, or analysis populations were handled inappropriately. It means their handling is not reported in the registry record and cannot be evaluated from it.

12. Safety Results

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

Other (non-serious) adverse events

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

The adverse-event record lists 0 serious events and 0 other events for the liberal-use group, with 409 at risk. For the indicated-use group, it lists 0 serious events and 0 other events, with 435 at risk. These are adverse-event entries, not results for the primary cesarean-delivery endpoint.

Zero recorded events should be read as the event counts entered in the registry, not as proof that no adverse events occurred in the full study or that the strategies have no safety risks. The record does not report serious adverse-event terms, and the list of top serious terms is empty. Death counts are not reported in the registry record.

In general, safety counts depend on how events were defined, collected, and entered, as well as on the period of observation. The record does not describe those procedures or provide event-specific detail. The figures therefore offer only a limited account of what was entered in the adverse-event record; they do not support a broad comparison of safety between the strategies.

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

This record documents a study asking whether indicated rather than liberal maternal oxygen use during labor was associated with a change in cesarean delivery. It identifies the primary endpoint and describes the strategies being compared. It also records a completed, nonrandomized controlled before-and-after study with enrollment of 844. These details explain the question and the general design, but do not establish the study’s findings.

The primary cesarean outcome results are not reported in the registry record. Without the group outcome counts, estimated contrast, and uncertainty, readers cannot determine whether the recorded data favored either strategy, how large any difference might have been, or how precisely it was estimated. The study’s stated hypothesis about lower cesarean delivery and fetal acidemia is a rationale for the research question, not a reported result.

Even if a comparative estimate were available, nonrandomized allocation would require attention to confounding and period effects. The groups might differ for reasons beyond oxygen use, and the record does not report enough detail to assess comparability, adjustment, or changes in care over time. Statistical precision, if reported, would not by itself resolve those design limitations.

For the same reasons, the record cannot establish that one oxygen strategy causes a change in delivery or newborn outcomes. It also cannot establish equivalence or absence of an effect: a missing result is not evidence that outcomes were the same. The adverse-event entries list zero counts, but their limited detail does not establish overall safety.

The appropriate reading is therefore bounded. The registry defines a clinically relevant comparison and records its design, but does not provide outcome evidence for judging effectiveness or the magnitude of any association. Any stronger conclusion would require results and methodological details not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable because it addresses a clinical practice comparison through a nonrandomized controlled before-and-after design. Such designs can examine changes associated with a practice strategy, but they require careful attention to how the comparison groups were formed and what else changed over time. The registry identifies the design clearly enough to signal that causal interpretation needs caution.

The primary outcome is a direct delivery endpoint: whether a participant delivered by cesarean. The registry also distinguishes this overall count from cesarean delivery for non-reassuring fetal status and lists measures of fetal, newborn, and maternal care. That range of outcomes reflects several different dimensions of the study question; they should not be treated as interchangeable evidence for a single claim.

The record also illustrates the difference between a registered question and an interpretable result. It names an endpoint and records enrollment, but does not report the outcome counts, effect estimate, uncertainty, or analysis methods. Without those pieces, even a clearly defined question cannot yield a quantitative conclusion. Completion status is administrative information, not a statistical finding.

Finally, the planning assumptions are explicitly illustrations based on an observed effect rather than evidence of the original design or observed power. This distinction matters when readers encounter sample-size calculations: they describe hypothetical planning conditions, not the strength of evidence in the completed comparison. The record’s missing analysis and results information limits further evaluation.

15. 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.

The main limitation for interpreting this specific study is the absence of reported primary and secondary outcome results. The registry record does not provide the cesarean-delivery counts, effect estimates, confidence intervals, or tests needed to assess the intended comparison. It also lists zero analyses, so no analytic approach can be evaluated from the registry entries.

Nonrandomized allocation is a design limitation for causal interpretation. The record identifies a controlled before-and-after structure but does not report the boundaries of the periods, participant selection procedures, baseline characteristics, or adjustment for differences between groups. It is therefore not possible to assess whether the groups were comparable or whether time-related changes could explain an observed contrast.

Descriptions of the intervention are not fully symmetrical in detail. The liberal strategy allowed oxygen with any category 2 tracing at clinician discretion, while the indicated-use description lists selected criteria but ends before its full wording is complete. The record does not report how adherence to either strategy was measured or whether actual oxygen exposure matched the assigned policy.

Information needed to assess outcome completeness is also absent. The record does not report primary endpoint denominators, missing-data handling, analysis populations, or a statistical analysis plan. It does not report how multiple outcomes were handled. These gaps limit assessment of selection bias, outcome ascertainment, and the possibility of selective emphasis.

Finally, the adverse-event entries have no event terms and do not report death counts. They should not be treated as a comprehensive safety analysis. These registry limitations do not prove that procedures were absent from the research itself; they indicate that the relevant details are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Comparative Effectiveness of Liberal Versus Restricted Maternal Administration of Oxygen During Labor — NCT02752490.
• Registry record last updated 2020-10-12; status last verified 2020-10.
• Results first posted 2018-03-02.
• 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.

19. Record Summary

The registry describes a completed nonrandomized controlled before-and-after study of liberal versus indicated maternal oxygen use during labor. The recorded enrollment is 844. The study began in 2016-04, with primary completion on 2016-07-31. The sponsor is The University of Texas Health Science Center, Houston; masking is listed as none and the model as parallel.

The primary endpoint is the number of participants who delivered by cesarean at birth. Secondary outcomes cover fetal, newborn, and maternal measures. The registry record does not report primary or secondary outcome results, analysis methods, missing-data handling, or analysis populations. It lists zero analyses. The adverse-event entries list zero serious and zero other events in each group, but provide no event terms; deaths are not reported. Consequently, the record defines the research question and design without establishing the comparative outcome or its precision.