Trans-abdominal Fetal Pulse Oximetry: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trans-abdominal Fetal Pulse Oximetry (NCT05147584), a na na study. The primary outcome is Fetal Oxygen Levels.

2. Clinical Question

The central question is one of measurement feasibility: could the sensors obtain fetal-signal data of adequate quality during labor for paired analysis? That is distinct from asking whether fetal oxygen measurements agree with CTG, identify a clinical condition, or improve decisions or outcomes. Although retrospective CTG comparison is described in the arm description, results for such a comparison are not reported in the registry record.

3. Trial Design

Trans-abdominal Fetal Pulse Oximetry, also titled Trans-abdominal Fetal Pulse Oximetry: PILOT 1, is registered as a single-group device study. Allocation is listed as not applicable, and masking is listed as none. The record names one intervention, dual fetal oxygen sensors, and describes use of internal and external sensors during active labor. Sensor recordings were to be compared retrospectively with CTG.

The registry lists an enrollment of 31 and describes 23 participants as having completed the monitoring period. It states that all 23 subject files were analyzed, while 15 participants had adequate paired data for fetal-signal analysis. The record does not explain the status or data availability of participants who did not complete monitoring, nor does it provide a participant flow account beyond these statements.

The study began on 2022-07-20, had a primary completion date of 2023-11-29, and is listed as terminated. A reason for termination is not reported in the registry record. The record lists fetal hypoxia, fetal distress, fetal acidemia, and fetal or neonatal effect of complication of labor among the conditions.

A single-group pilot can describe whether measurements can be obtained and characterize the available data. It cannot, by design alone, provide a randomized estimate of a treatment effect. The registry does not report a concurrent randomized control group, an allocation procedure, or masking. It also does not report a protocol rationale for the enrollment target, the intended number of centers, or details of the monitoring workflow beyond the sensor and CTG 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All 23 subject files were analyzed. Of the 23 participants who completed the monitoring period, 15 were considered to have adequate paired data for analysis of fetal signal.

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.

Population: 23 Females participated

6. Primary Endpoint

The registry lists the primary outcome as Fetal Oxygen Levels, measured over During labor.

The primary outcome is titled Fetal Oxygen Levels, is measured in participants, and is described as assessing the adequacy of fetal signals from both internal and external fetal oxygen sensors during labor. In the registry’s outcome description, 15 participants are identified as having adequate paired data for fetal-signal analysis, among the 23 participants who completed monitoring.

Signal adequacy is a measurement-feasibility outcome: it indicates whether the collected signals were considered usable for the intended paired analysis. For a device study, this can help distinguish the ability to acquire analyzable measurements from later questions about what those measurements mean clinically. A signal judged adequate is not, by itself, evidence that the sensor accurately classifies fetal oxygenation or improves care.

The registry does not report the operational definition or threshold used to classify a signal as adequate. It also does not give separate adequacy results for the internal and external sensors, or report a quantified comparison of sensor measurements with CTG. Those details would be needed to interpret the classification procedure and assess agreement or diagnostic performance. The primary outcome therefore supports a limited reading about availability of paired signal data, not a conclusion about clinical validity.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count describe?

The primary outcome is expressed as a count of participants with an event, where the event is adequate paired fetal-signal data. A count is a direct description of how many participants met the outcome definition. Its interpretation depends on a clear definition of the event and a clear denominator: readers need to know who was assessed, which records were eligible, and how missing or unusable data were handled. The registry gives counts for completed monitoring and adequate paired data, but does not report a complete account of the classification rules or missing-data handling.

A count alone does not measure uncertainty in the way an interval estimate does. A confidence interval generally gives a range of values compatible with the observed data under a statistical model and specified assumptions. It helps readers judge how precisely an underlying quantity has been estimated. No confidence interval for signal adequacy is reported in the registry record. Without one, the posted count should be treated as a descriptive result from this study, not as a precise estimate of performance in a broader population.

Why does the endpoint definition matter?

For device feasibility, signal adequacy is an intermediate measurement outcome. The classification separates records deemed suitable for paired analysis from records that do not meet the adequacy criterion. The threshold, review process, and whether assessment was blinded can influence that classification. The registry record does not report the adequacy threshold, the review procedure, or a blinded adjudication process. These omissions prevent readers from determining whether the outcome could be applied consistently or reproduced in another study.

Paired data are useful when two measurements are intended to be compared within the same monitoring period or participant. A paired design can account for the fact that observations from the same participant are related rather than independent. The record says that 15 participants had adequate paired data, but does not provide the paired measurements or describe the planned statistical comparison with CTG. No agreement estimate or analysis of paired differences is reported.

What can a single-group design establish?

A single-group study can describe data acquisition and the observed characteristics of participants or measurements. It does not include a randomized control group for estimating a causal treatment effect. Here, the registry describes retrospective comparison with CTG, but this should be distinguished from randomization: CTG is not listed as a separately allocated trial arm. A measurement comparison may be informative about agreement or feasibility if the methods and results are reported, but those results are not reported in the registry record.

Masking can reduce the influence of knowledge about one measurement on interpretation of another. Masking is listed as none. The record does not state whether signal adequacy was assessed by personnel who knew the CTG findings, whether any independent review occurred, or how subjective judgments were managed. These details matter when an endpoint depends on judging signal quality.

How should the planning assumptions be read?

The registry’s sample-size assumptions describe a planning illustration computed from an observed effect, rather than the original design justification for this pilot. The stated illustration uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Those assumptions describe a hypothetical planning exercise and do not describe the actual single-group design. The registry does not report the protocol’s sample-size justification, and the planning illustration is not observed power.

Power is a design property calculated for a specified effect, variability, significance threshold, and analysis. It is not a measure of how likely the observed result is true, and calculating power after observing data does not resolve uncertainty in the result. Planning estimates can illustrate how study size might relate to a target effect under assumptions, but they do not change the evidential strength of the actual study. No planning estimate values are reported in the registry entries summarized for this analysis.

Why can over-dispersion matter?

For count outcomes, a statistical model may assume that variability follows a particular relationship to the average count. Over-dispersion means the observed variation is greater than that model expects. If ignored, standard errors may be too small and intervals or tests may appear more precise than warranted. This is a general concern for count-data analyses, not a reported feature of this trial. The primary outcome is described as a count of participants, and the registry does not report a count-model analysis or any assessment of over-dispersion.

More broadly, the record lists no analysis entries, statistical test, confidence interval, adjustment, or model for the primary outcome. No analysis method should be inferred from the endpoint title or the retrospective CTG comparison description. The posted evidence is therefore descriptive, and a more detailed statistical interpretation would require outcome definitions, analysis procedures, and results that are not reported in the registry record.

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("Interventional/Observational")
n      <- c(23)
events <- c(15)
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  Interventional/Observational  23  15  65.2  42.7  83.6  44.9  81.2  44.7  81.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, but the record does not report a multiplicity strategy. When a study assesses multiple outcomes, testing each one can increase the chance of a false-positive finding if each is interpreted as a separate confirmatory test. General approaches include defining one primary hypothesis in advance, adjusting inference across a family of tests, or treating analyses as exploratory. Which approach was planned for this study is not reported in the registry record. No multiplicity adjustment or outcome hierarchy beyond the primary outcome designation is described.

Missingness requires similar care. The record lists enrollment of 31, says that 23 participants completed monitoring, and reports adequate paired data for 15 participants. It does not explain the disposition of participants who did not complete monitoring, whether all collected data were usable, or why some paired data were not considered adequate. These counts should not be used to infer a reason for missing or inadequate data.

The record states that all 23 subject files were analyzed, but does not define the analysis population, specify an intention-to-treat or per-protocol approach, or describe how incomplete records were handled. It does not report imputation, sensitivity analyses, or a comparison of participants with and without adequate paired data. These omissions limit assessment of selection bias: if the availability of analyzable signals is related to participant or labor characteristics, the analyzed data may not represent all monitored participants. Whether that occurred cannot be determined from the registry record.

12. 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 adverse-event record lists the Interventional/Observational group with 23 participants at risk for serious adverse events and 0 affected. It also lists 23 at risk for other adverse events and 0 affected, with 0 deaths. No serious adverse-event terms are listed.

These are registry-reported counts for the group and should be read as such. They do not establish that no event could occur, or that the device has no safety risks. A count of zero in a study of this size can coexist with uncertainty about uncommon events, and the record does not provide a precision estimate for these safety counts. The registry record also does not describe event-collection procedures, the observation window for adverse events, severity grading beyond the serious-event classification, or causal assessments.

The number at risk in the safety listing is not a substitute for the primary-outcome analysis population. The record presents safety and signal-adequacy information for different purposes. No comparison with another group is available, so the safety counts do not support a relative-risk estimate.

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

The result supports a narrow descriptive statement: the registry reports that 15 participants had adequate paired data for fetal-signal analysis, among 23 participants who completed monitoring. This is relevant to whether analyzable paired signals were obtained in the study. The record does not define the adequacy threshold in sufficient detail to establish how that classification would perform under other procedures or in other settings.

The result does not establish that the device accurately measures fetal arterial oxygen saturation, detects fetal hypoxia, or predicts fetal distress or fetal acidemia. Those conditions are listed in the record, but no diagnostic accuracy or clinical-outcome results are reported. The record also does not report a quantified comparison with CTG, despite describing retrospective comparison as part of the study procedure.

Nor does the result demonstrate an effect on clinical management or outcomes. The study has a single-group design and no randomized comparison. Its measurement-feasibility question is distinct from whether use of the sensor changes decisions or benefits participants. No treatment-effect estimate, adjusted analysis, or inferential test is reported.

Precision cannot be assessed from the posted count alone. The registry does not report an interval estimate or an analysis accounting for uncertainty. The enrollment and completion counts also do not explain the full path from monitoring to usable paired data. The status of terminated does not supply that explanation, and the reason for termination is not reported in the registry record.

Accordingly, the appropriate interpretation is limited to the available descriptive account of signal-data adequacy. Claims about device accuracy, clinical usefulness, comparative performance, or safety beyond the recorded event counts would require methods and results that are not reported.

14. Why This Trial Matters Statistically

Feasibility outcomes are important in early device research because later evaluations depend on obtaining usable measurements. A sensor may be intended to provide information alongside an existing monitoring approach, but evaluation of that role first requires clear evidence about data acquisition and signal quality. This study’s reported count of participants with adequate paired data addresses that preliminary measurement question, albeit without a reported adequacy threshold or detailed analysis.

Statistically, feasibility and clinical effectiveness are different targets. Signal availability describes whether data could be analyzed; diagnostic performance asks how well measurements classify a target condition; clinical effectiveness asks whether using the device changes outcomes. Each requires its own outcome definition, analysis, and uncertainty assessment. The registry record reports only limited descriptive information for the primary signal outcome and does not report CTG agreement or clinical results.

The record also illustrates why transparent reporting of participant flow and analysis populations matters. Enrollment, completion, and adequate paired data refer to different stages of the evidence. Clear reasons for non-completion or inadequate data, together with explicit classification rules, would help readers assess selection and reproducibility. Those details are not reported in the registry record.

Finally, a pilot result should be interpreted in light of design and precision. The single-group design cannot supply a randomized causal comparison, and no confidence interval or inferential analysis is reported. These limits do not make the descriptive finding irrelevant; they define the scope of the question it can answer. The record is informative about the existence of analyzable paired signals in this study, but not about whether the technology provides accurate or clinically beneficial information.

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.

Several limitations specific to this record constrain interpretation. First, the endpoint is described as adequacy of paired fetal signals, but the registry does not report the threshold, quality criteria, or review procedure used to classify data as adequate. The outcome therefore cannot be independently reproduced from the description alone.

Second, the record reports 23 participants completing monitoring and 15 with adequate paired data, but does not detail participant flow or explain why monitoring was not completed by everyone enrolled, or why some completed records did not contribute adequate paired data. Missing-data handling and analysis-population definitions are not reported.

Third, the retrospective CTG comparison is described as a procedure, but no comparison results are reported. There are no posted estimates of agreement, diagnostic performance, or clinical outcomes. Masking is listed as none, and the record does not explain whether knowledge of CTG findings could influence assessment of signal adequacy.

Finally, the registry lists the study as terminated without reporting a reason. It also lists no analysis entries. Protocol details, a statistical analysis plan, a sample-size justification, and inferential estimates are not reported in the registry record. These gaps prevent readers from assessing prespecification, precision, or the reasons the study ended. The limitations should be understood as limits of the reported record, not as evidence about unreported study conduct.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Trans-abdominal Fetal Pulse Oximetry — NCT05147584.
• Registry record last updated 2025-02-04; status last verified 2025-01.
• Results first posted 2025-02-04.
• 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

Trans-abdominal Fetal Pulse Oximetry: PILOT 1 is a terminated, single-group device study of dual fetal oxygen sensors used during active labor. The registry describes retrospective comparison with CTG and lists no masking. The study began on 2022-07-20, with primary completion on 2023-11-29.

The registry reports enrollment of 31, completion of monitoring by 23 participants, and adequate paired fetal-signal data for 15 participants. It lists 0 serious adverse events, 0 other adverse events, and 0 deaths in the group reported. No analysis entries are listed. Definitions of signal adequacy, CTG comparison results, inferential analyses, missing-data methods, and the reason for termination are not reported in the registry record.