This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Ultrasound Prediction of Prolonged Labour (NCT00915148), a registered phase not stated study. The primary outcome is Area Under the Receiver Operating Curve (ROC AUC) Values for Prediction of Vaginal Delivery Using 2D or 3D Ulrasound.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00915148 |
| Phase | Phase not stated |
| Condition | Prolonged Labor |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 110 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Helse Stavanger HF |
| Results posted | Yes |
2. Clinical Question
Population
Women with prolonged labour were the study population. The listed eligibility description specifies primigravidae with a single pregnancy, a live fetus in cephalic presentation, and gestation >37 weeks. The registry reports enrollment of 110 participants.
Intervention
The recorded study procedure was an ultrasound examination. Fetal-head descent was measured using the distance between the outer bony limit of the fetal skull and the perineum, and was also assessed using the angle of progression in a mid-sagittal plane.
Comparator
The study description says ultrasound findings would be correlated with manual palpation. The registry does not describe a randomized control group or a like-for-like comparison between treatment arms. Manual palpation is therefore best understood as a measurement to be correlated, not as a randomized comparator.
Primary question
The primary question was whether ultrasound measurements of fetal-head descent could discriminate between women who did and did not have a vaginal delivery. The registry identifies receiver operating characteristic area under the curve values for prediction of vaginal delivery using 2D or 3D ultrasound as the primary outcome. Its listed timeframe is during labour.
3. Trial Design
This was a completed observational study, not a randomized treatment comparison. The registry lists an ultrasound examination and describes the purpose as relating ultrasound findings to manual palpation and considering whether delivery outcome could be predicted using ultrasound. Its focus was fetal-head level, or descent, in the pelvis during prolonged labour.
The registry reports 110 participants enrolled. The listed population is primigravidae with a single pregnancy, a live fetus in cephalic presentation, and gestation >37 weeks. The condition is prolonged labour. The sponsor is Helse Stavanger HF. The record lists a start date of 2008-11, primary completion in 2010-08, and status as completed.
Two outcome measures and two analyses are recorded. The primary outcome concerns ROC AUC values for prediction of vaginal delivery, and a secondary outcome concerns the percentage of women with delivery within 6 hours from defined prolonged labour in accordance with WHO recommendations. The registry does not report the detailed analysis methods, the criteria used to define prolonged labour, or the exact timing and process for obtaining measurements beyond the stated timeframe during labour.
Because the study is observational, its design can describe associations and predictive performance, but does not establish that an ultrasound measurement causes a delivery outcome. The registry does not report a protocol, a sample-size justification, or a planned analysis population. Details about participant recruitment, clinician blinding, measurement training, and handling of repeat measurements are not reported in the registry record.
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.
Before assignment: No participants were excluded
Overall Study
| Stage | Women With Prolonged Labour |
|---|---|
| STARTED | 110 |
| COMPLETED | 110 |
| NOT COMPLETED | 0 |
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.
| Characteristic | Unit | Women With Prolonged Labour |
|---|---|---|
| Participants analysed | 110 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 110 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 29 (18 to 41) |
| Sex: Female, Male: Female | Participants | 110 |
| Sex: Female, Male: Male | Participants | 0 |
| Region of Enrollment: Norway | participants | 110 |
6. Primary Endpoint
The registry lists the primary outcome as Area Under the Receiver Operating Curve (ROC AUC) Values for Prediction of Vaginal Delivery Using 2D or 3D Ulrasound, measured over during labor.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage probability |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is described as the area under the receiver operating characteristic curve for predicting vaginal delivery using 2D or 3D ultrasound. The measurements include fetal head-perineum distance and angle of progression. The registry states that the distance measure was evaluated using a cut-off of ≤40 mm and the angle of progression using a cut-off of ≥ 110 degrees. It describes ROC curves as plotting sensitivity against the false positive rate.
As a general statistical concept, an ROC curve shows how sensitivity and false positive rate change across possible decision thresholds. The AUC condenses this curve into a measure of how well a marker separates people with different outcome classifications, without requiring one threshold to represent every possible use. It is a measure of discrimination, not a direct measure of calibration, clinical benefit, or causality.
A confidence interval communicates uncertainty around an estimated AUC. Its width indicates the precision of that estimate: a wider interval reflects greater uncertainty. The registry identifies a 95% confidence interval as the dispersion measure, but the actual AUC estimates and intervals are not reported in the registry record. Consequently, the endpoint’s definition can be described, but its observed predictive performance cannot be assessed from the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry frames the study as an assessment of whether ultrasound measurements of fetal-head descent can predict vaginal delivery during prolonged labour. It reports the intended primary outcome as ROC AUC values for 2D or 3D ultrasound and identifies two measurement approaches: fetal head-perineum distance and angle of progression. It also states the cut-offs used to evaluate those measures: ≤40 mm and ≥ 110 degrees, respectively.
However, the registry record does not report the resulting AUC values, confidence intervals, sensitivity, or false positive rates. It therefore does not show how well either ultrasound measurement discriminated between delivery outcomes, how precisely any estimate was determined, or whether one measurement performed differently from another. The stated cut-offs alone do not reveal how many participants met them or how accurately they classified the outcome.
The secondary outcome concerns delivery within 6 hours from defined prolonged labour in accordance with WHO recommendations. The result for that outcome is not reported in the registry record. The definition and measurement procedure for the start of the 6-hour period are also not reported in the registry record, so the outcome cannot be interpreted in detail from the record.
As a general statistical point, a point estimate describes the observed result in a sample, while its confidence interval indicates the range of values compatible with the data under the analysis assumptions. A narrow interval generally conveys more precision than a broad one, but neither an estimate nor an interval is a guarantee about performance in another population. Here, neither the point estimates nor their intervals are available in the registry results described.
The study enrolled 110 participants, but the registry does not state how many contributed to each analysis or whether all enrolled participants had complete ultrasound and delivery data. The precision and representativeness of any analysis therefore cannot be inferred from enrollment alone. There is also no reported statistical comparison establishing whether the 2D and 3D approaches differed. The registry identifies two analyses, but their specifications and results are not reported in the registry record.
Overall, the available information describes a prediction question and its measurement framework, not a demonstrated level of predictive accuracy. The findings should not be characterized as showing that ultrasound does or does not predict vaginal delivery. The relevant outcome estimates and their uncertainty are not reported in the registry record.
9. Statistical Methods Explained
What does the ROC AUC represent?
As a general statistical concept, a receiver operating characteristic curve describes classification performance across decision thresholds. Sensitivity is the proportion of people with the target outcome who are classified as positive. The false positive rate is the proportion without the target outcome who are classified as positive. The registry says its curves plotted sensitivity against false positive rate for the ultrasound measures.
The area under that curve, or AUC, summarizes discrimination across thresholds. It concerns how well a marker tends to rank people with different outcome statuses. It does not by itself tell a reader which threshold should be used, how closely predicted probabilities match observed outcome frequencies, or what consequences a classification would have. Those are distinct questions requiring additional information and, for some of them, additional analyses.
How do the recorded measurements relate to classification?
The registry describes fetal head-perineum distance as the shortest distance between the outer bony limit of the fetal skull and the perineum. It says fetal-head descent was reassessed by measuring the angle of progression in a mid-sagittal plane. The distance was evaluated with a cut-off of ≤40 mm, while the angle was evaluated with a cut-off of ≥ 110 degrees. These are measurement thresholds recorded for the study. The registry does not report the number of participants on either side of either threshold or the classification results at those cut-offs.
In general, changing a classification threshold can alter sensitivity and false positive rate: a threshold that classifies more observations as positive may identify more people with the outcome while also classifying more people without it as positive. The balance depends on the data and the threshold. No such trade-off can be quantified for this study from the outcome information reported in the registry.
What does the confidence interval add?
The registry specifies a 95% confidence interval for the primary outcome. In general, a confidence interval expresses statistical uncertainty around an estimate under the model and sampling assumptions used to calculate it. The interval is not a statement that a particular future patient’s outcome will fall within its limits. Nor does it account automatically for systematic errors such as inconsistent measurement or selection of participants.
For an AUC, the interval would help readers assess how much precision the study achieved in estimating discrimination. The interval endpoints and the AUC estimates are not reported in the registry record, so neither precision nor compatibility with different levels of discrimination can be assessed.
What can be inferred from the study design?
As a general principle, observational prediction studies evaluate how measurements relate to outcomes in the observed population. Their predictive findings do not establish that changing a measurement, or acting on it, changes an outcome. This study is described as observational and as correlating ultrasound findings with manual palpation. The registry does not report random assignment or a randomized treatment comparison.
The registry does not report the exact statistical models, whether thresholds were specified before analysis, or whether prediction performance was assessed in a separate validation sample. These details matter because performance estimated in the same data used to develop or select a model can be optimistic, and results may not transfer to other settings. Whether such procedures were used is not reported in the registry record.
The record also contains sample-size assumptions for a planning illustration: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. Such an illustration is not the study’s own design justification, does not describe observed power, and does not establish that this observational study had two randomized arms. The registry does not report the trial’s sample-size justification. No planning sample-size values are reported in the registry record in the information available for interpretation.
In general, over-dispersion matters when count data vary more than a statistical model expects; ignoring it can make uncertainty estimates too small. The registry’s outcome type is not reduced to one comparison, but it does not report a count model or evidence of over-dispersion. This concept therefore cannot be connected to a specific analysis result in this study.
Finally, a statistically precise estimate would not alone establish usefulness. Interpretation also depends on the outcome definition, measurement reliability, population, and the purpose for which predictions would be used. The registry record does not report enough outcome results or analysis detail to make those assessments for this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists two outcome measures and two analyses. It identifies the primary outcome as ROC AUC values for prediction of vaginal delivery using 2D or 3D ultrasound, and the secondary outcome as delivery within 6 hours from defined prolonged labour. The analysis details and results for these outcomes are not reported in the registry record.
Multiplicity arises when several outcomes, measurements, thresholds, or analyses are examined. As a general statistical issue, conducting multiple analyses can increase the chance that at least one result appears notable by chance. A prespecified hierarchy or adjustment can address some multiplicity concerns, but the registry does not report a multiplicity plan, adjustment, or rationale for how results across 2D and 3D ultrasound or the two measurements were to be interpreted.
The registry does not report how missing ultrasound measurements or missing delivery outcomes were handled. It also does not report the number of participants included in each analysis, whether any participants were excluded after enrollment, or whether imputation or another missing-data method was used. These details are important because analyses restricted to participants with complete information can differ from the enrolled group if data availability is related to participant characteristics or outcomes.
The analysis population is not reported in the registry record. It is therefore not possible to determine whether each analysis included all enrolled participants or a defined subset. The protocol, prespecified analysis plan, and any interim analyses are also not reported in the registry record. Without those details, it is not possible to assess whether the reported analyses followed a prespecified plan or whether additional analyses were undertaken.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Women With Prolonged Labour | 0 | 110 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Women With Prolonged Labour | 0 of 110 |
The registry lists 110 women with prolonged labour at risk for serious adverse events and records 0 affected. It also records 0 other adverse events among 110 at risk. No serious adverse-event terms are listed. These are the counts recorded in the registry; they do not, on their own, establish that adverse events were actively or completely ascertained.
As a general statistical point, an observed count of zero does not prove that the underlying event risk is zero. The interpretation depends on how events were defined, how participants were monitored, the duration and completeness of follow-up, and whether all events were entered in the registry. Those ascertainment and follow-up details are not reported in the registry record.
Deaths are not reported in the registry record. The zero counts should be read as registry-reported event counts, not as evidence that the study ruled out rare harms or that the ultrasound examination is risk-free. The study is observational, and the registry does not describe a randomized safety comparison.
12. What the Result Does, and Does Not, Mean
The record documents a completed observational study of ultrasound measurements of fetal-head descent during prolonged labour. Its primary question concerns discrimination for vaginal delivery using 2D or 3D ultrasound. The registered measurement descriptions include fetal head-perineum distance and angle of progression, with cut-offs of ≤40 mm and ≥ 110 degrees. The study enrolled 110 participants.
Those details establish what the investigators intended to measure and the population to which the question applied. They do not establish the observed accuracy of either ultrasound measure. The registry does not report AUC estimates, confidence intervals, sensitivity, false positive rates, or the secondary outcome result. Accordingly, the record does not support a conclusion about whether either measure predicted delivery outcome well, whether the measures differed, or how precise any estimates were.
As a general distinction, prediction is not causation. Even if a marker is associated with an outcome or discriminates between outcome groups, that alone does not show that using the marker changes the outcome. The registry describes an observational assessment and does not report a randomized comparison of ultrasound-guided care with another approach.
The results also cannot be assumed to apply beyond the listed population. The registry describes primigravidae with a single pregnancy, a live fetus in cephalic presentation, and gestation >37 weeks, in the context of prolonged labour. Generalizing beyond that population would require evidence not reported in the registry record.
The appropriate interpretation is therefore limited: the record identifies a clinically framed prediction question, its ultrasound measures, and the enrolled population, but does not report the primary or secondary outcome results needed to judge predictive performance. It neither demonstrates benefit nor establishes lack of benefit.
13. Why This Trial Matters Statistically
This study raises a statistical question that is distinct from testing whether a treatment changes an outcome: can a measurement help distinguish between people who later have different delivery outcomes? That distinction matters because predictive performance is evaluated through discrimination and uncertainty, while causal claims require a design and analysis suited to estimating effects of an intervention.
The registry’s focus on fetal-head descent also illustrates why an outcome measure needs a clear operational definition. It describes both a distance and an angle, along with specified thresholds. A reader needs not only the chosen measurements but also their estimated performance, precision, and analysis context to assess what the markers contribute. Those results are not reported in the registry record.
The record also highlights the difference between a registered study question and a reported result. A completed status and an enrollment count do not substitute for outcome estimates. Without the AUC values and confidence intervals, the registry cannot establish whether the prediction estimates were precise or how the two measurement approaches compared.
Finally, the observational design is relevant to the scope of conclusions. A marker may be associated with an outcome without showing that acting on the marker would alter that outcome. Separating prediction from causation helps prevent an accuracy question from being interpreted as evidence of treatment effect. The study is statistically relevant because it makes that distinction central, even though the available registry results do not resolve the prediction question.
14. 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 most important limitation for interpreting the registry record is that the primary outcome estimates and their 95% confidence intervals are not reported in the registry record. The registry also does not report sensitivity, false positive rates, or results for the secondary outcome. Consequently, the central predictive question cannot be answered from the reported outcome information.
The analysis methods are incompletely described. The registry does not report how the ROC analyses were calculated, how the comparison between 2D and 3D ultrasound was conducted, whether cut-offs were prespecified, or whether prediction performance was validated. It also does not report how measurements were standardized, whether assessors were blinded to other findings, or how repeat or uncertain measurements were handled.
The record describes a specific population: primigravidae with a single pregnancy, a live fetus in cephalic presentation, gestation >37 weeks, and prolonged labour. Findings from that population may not generalize to people outside those eligibility characteristics. Recruitment procedures and the detailed definition of prolonged labour are not reported in the registry record.
Participant flow and analysis denominators are not reported in the registry record. Although 110 participants were enrolled, it is not stated how many had complete data for each analysis. The missing-data approach and analysis population are also not reported. In an observational study, unmeasured differences and measurement practices may affect observed associations; the registry does not report methods for addressing those concerns.
These limitations concern what can be concluded from the registry record. They do not establish that the underlying study failed to collect or analyze information; the relevant details are simply not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Ultrasound Prediction of Prolonged Labour — NCT00915148.
- Registry record last updated 2016-04-26; status last verified 2016-04.
- Results first posted 2016-04-26.
- 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.
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18. Record Summary
The registry describes a completed observational study sponsored by Helse Stavanger HF, with 110 participants enrolled. The study examined ultrasound measurement of fetal-head descent during prolonged labour and its relation to vaginal delivery. The listed population was primigravidae with a single pregnancy, a live fetus in cephalic presentation, and gestation >37 weeks.
The primary outcome was ROC AUC for prediction of vaginal delivery using 2D or 3D ultrasound. Measures included fetal head-perineum distance and angle of progression. The secondary outcome concerned delivery within 6 hours from defined prolonged labour. The primary and secondary outcome results, confidence intervals, detailed analysis methods, missing-data handling, and analysis populations are not reported in the registry record.