A Study Comparing Vaginal Misoprostol and Intravenous Oxytocin for Induction of Labor: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study Comparing Vaginal Misoprostol and Intravenous Oxytocin for Induction of Labor (NCT01634854), a randomized na study. The primary outcome is Time From Induction to Vaginal Delivery.

2. Clinical Question

The clinical question is comparative rather than a test of either medication against no induction. It asks whether the distribution of time to vaginal delivery differs between the medication strategies in the stated population. The posted primary result summarizes each group with a median and inter-quartile range and reports a Wilcoxon (Mann-Whitney) comparison.

The registry also lists neonatal and maternal outcomes, maternal satisfaction, excessive uterine activity necessitating treatment, and neonatal intensive care admission with a low APGAR score at 5 minutes. These outcomes add context to the comparison, but the registry record does not report results for every listed outcome. The primary comparison therefore addresses one specific measure of timing; it does not by itself summarize all maternal or neonatal outcomes.

3. Trial Design

The registry describes a randomized, parallel-group study with no masking. The interventions were vaginal misoprostol and intravenous oxytocin. The listed enrollment is 130. The posted primary outcome summaries list 62 participants in the vaginal misoprostol group and 59 in the intravenous oxytocin group. The registry record does not explain the relationship between its enrollment figure and the numbers included in those outcome summaries, so those figures should not be treated as interchangeable descriptions of the analysis population.

The study is marked completed. Its listed start is 2012-07 and its primary completion is 2014-05. The registry names Vanderbilt University Medical Center as sponsor. The phase is recorded as NA. No further study setting or site information is reported in the registry record.

The medication regimens are described in the record. Misoprostol was administered intravaginally, with doses and a stopping condition tied to cervical change consistent with active labor. Oxytocin was administered intravenously, with the infusion rate increased at stated intervals to establish an effective contraction pattern. The record does not describe additional care procedures or how clinicians determined that a contraction pattern was effective.

Randomization supports a planned comparison between groups, but the record does not report the randomization sequence method, allocation concealment, or stratification. Masking is listed as none, so the study was open label as recorded. How lack of masking may have affected care, outcome ascertainment, or participant-reported outcomes is not reported in the registry record. The registry also does not report the protocol, the sample-size justification, or details of the analysis population. These omissions limit the amount that can be concluded about how the study was planned and conducted beyond the design features explicitly recorded.

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:

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 Time From Induction to Vaginal Delivery, measured over Time to delivery in minutes from initiation of medication, up to 24 hours.

The primary endpoint is time from initiation of the medication to vaginal delivery, measured in minutes. The registry defines the timeframe as time to delivery from medication initiation, up to 24 hours. It compares this timing measure between the misoprostol and oxytocin groups.

Time to delivery is a direct way to describe the duration of the induction-to-delivery process. In this record, the endpoint is summarized with a median and inter-quartile range rather than a mean and standard deviation. The median identifies the middle of the observed distribution, while the inter-quartile range describes the spread of the central portion of that distribution. These summaries can be useful when values are skewed or when unusually long times could make a mean less representative of a typical observation.

The endpoint is specifically vaginal delivery after medication initiation. It should not be read as a comprehensive measure of labor experience, maternal health, neonatal health, or overall satisfaction. Those issues appear among the listed secondary outcomes, but the primary endpoint does not combine them. The registry record does not explain how observations without vaginal delivery within the stated timeframe were handled, or whether all recorded times were complete.

As a general statistical point, a time-to-event outcome can be analyzed in ways that account for incomplete follow-up or events that do not occur within a defined observation period. The posted primary analysis is described as a Wilcoxon (Mann-Whitney) test and the group summaries are medians with inter-quartile ranges. The record does not report a separate time-to-event model or provide further details on handling the 24-hour timeframe.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a duration: time from medication initiation to vaginal delivery, recorded in minutes. The registry summarizes the outcome within each group using the median and inter-quartile range. The median is the value at the center of an ordered set of observations. The inter-quartile range runs from the lower to the upper quartile and describes the spread of the middle part of the observations. Together, these statistics provide a description of location and variability without requiring the distribution to be symmetric.

As a general statistical point, the mean can be sensitive to a small number of unusually large or small values. A median is less affected by extreme observations. That makes median-based summaries a reasonable descriptive choice for duration outcomes that may be unevenly distributed. However, the median and inter-quartile range do not describe every feature of a distribution. They do not reveal all possible clustering, gaps, or tails, and they do not alone quantify uncertainty in the difference between groups.

The registry reports a Wilcoxon (Mann-Whitney) test for the primary comparison. In general, this rank-based test orders observations across groups and evaluates whether values from one group tend to rank differently from values in the other group. It does not require the same assumptions about normality as a conventional comparison of means. A significant rank-test result is not automatically evidence that the group medians differ by a particular amount. Its interpretation relates to the ordering of observations and, under suitable distributional assumptions, to a location shift. The registry record does not state whether those assumptions were assessed.

The posted p-value is 0.11. A p-value is calculated under a specified null hypothesis and statistical model. It expresses how unusual the test statistic, or a more extreme one, would be if the null model held. It is not a measure of the probability that the observed difference occurred by chance, and it does not report the probability that one intervention is better. A p-value should be interpreted alongside effect estimates, uncertainty intervals, study design, and the outcome's relevance. The record does not report a confidence interval or an estimated contrast for the primary endpoint, which restricts direct assessment of the contrast's precision.

As a general explanation, a confidence interval gives a range of values compatible with the data and the interval's statistical procedure. Its width reflects precision: a wider interval indicates that the data leave more uncertainty about the quantity being estimated. No primary confidence interval is reported in the registry record, so precision cannot be described using that tool for this outcome. The group inter-quartile ranges describe variability in individual outcomes; they are not confidence intervals for the difference between groups.

The registry reports a randomized parallel-group design and no masking. Random allocation is intended to make groups comparable on average at the start of a study, including with respect to factors that are measured and factors that are not measured. In practice, the strength of interpretation also depends on how randomization was implemented, whether assigned groups were retained in the analysis, and how missing outcomes were handled. The sequence method, allocation concealment, analysis population, and missing-data procedures are not reported in the registry record.

No masking is recorded. In general, lack of masking can matter if knowledge of treatment assignment influences decisions about care, outcome assessment, or reporting. The primary endpoint is a time measure, but its timing and recording still depend on definitions and procedures. The registry gives a timeframe of up to 24 hours but does not describe how times beyond that period or participants without a vaginal delivery within the timeframe entered the analysis. The record also does not state whether outcome ascertainment was standardized across groups.

The posted secondary comparison for excessive uterine activity uses a binary outcome: whether a participant had the specified event. The record includes a risk-difference recalculation and an unadjusted p-value of 0.17. As a general point, a risk difference compares the observed event proportions by subtracting one group's proportion from the other's; an interval around that estimate expresses uncertainty. The posted interval for that comparison crosses zero, so it is compatible with no difference as well as with differences in either direction. This is a secondary result and should not be substituted for the primary timing analysis.

Planning illustrations for the excessive-uterine-activity comparison are based on the observed effect and stated planning assumptions, rather than on the trial's original design. They use a two-sided significance level of 0.05, equal allocation, and a normal approximation. For planning for 100% of the observed effect, the illustration gives 249 participants per arm for 80% power and 332 participants per arm for 90% power. For planning for 75% of the observed effect, it gives 478 participants per arm for 80% power and 639 participants per arm for 90% power. For planning for 50% of the observed effect, it gives 1,153 participants per arm for 80% power and 1,543 participants per arm for 90% power. These are planning illustrations, not observed power and not evidence that the original study was designed around those assumptions.

As a general statistical concern, binary outcomes with few events can have imprecise effect estimates. Over-dispersion is a separate issue that may arise when observed variation exceeds what a model assumes; accounting for it can prevent uncertainty from being understated. The registry record does not report a model for the primary duration outcome, a dispersion assessment, or an adjusted secondary analysis. It also does not report a multiplicity procedure for the collection of secondary outcomes. Those absences do not establish that no such procedures were used; they mean they are not reported in the registry record.

10. Analyses Reported by the Sponsor

The registry reports the sponsor's primary comparison as a Wilcoxon (Mann-Whitney) test with p = 0.11. The group medians and inter-quartile ranges are posted alongside that test. No separate recalculated primary contrast or primary confidence interval is reported in the registry record, so there is no independent primary recalculation to set against the sponsor's test result.

The posted recalculation concerns a secondary binary outcome, excessive uterine activity necessitating treatment. It is an unadjusted comparison based on the event counts and group sizes in the record, rather than the sponsor's reported primary timing analysis. Its estimate and interval are consequently not a substitute for the primary analysis, and it addresses a different question.

For the primary endpoint, the sponsor's reported analysis is the relevant inferential result available in the registry record. The p-value should be read together with the descriptive medians and inter-quartile ranges, while recognizing that no primary confidence interval is reported. A p-value does not convey the magnitude or precision of a difference by itself. The record does not provide additional details about the sponsor's statistical plan, the analysis population, or missing-data handling, so those aspects cannot be used to reinterpret or extend the reported test.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and 6 secondary outcomes. It does not report whether the analysis plan used a multiplicity adjustment, a hierarchy of outcomes, or another method for managing the interpretation of multiple comparisons. This absence matters because repeated testing can increase the chance of at least one apparently notable result when there is no underlying effect. Unadjusted secondary results should therefore be treated as exploratory unless further analysis-plan details are available in the registry record.

Missing-data handling is not reported in the registry record. The record does not state how incomplete measurements, withdrawals, or participants who did not reach vaginal delivery within the defined timeframe were handled. It also does not describe whether missingness was assessed by group or whether any sensitivity analyses were conducted. Without those details, it is not possible to determine how much the posted summaries depend on complete outcome recording.

The analysis population is not reported in sufficient detail to establish whether the primary comparison followed an intention-to-treat approach or another population definition. The registry lists enrollment as 130, while the posted primary outcome summaries give group sizes of 62 and 59. The record does not explain the difference between the enrollment figure and the outcome-summary group sizes. The figures should be understood as distinct record entries, not combined into a new total or interpreted as proof of a particular exclusion pattern.

Randomization is valuable for a comparison, but its protection against bias depends in part on preserving the randomized groups in analysis and accounting transparently for missing outcomes. The registry record does not report the randomization procedure, concealment, or analysis population. It also does not report interim analyses or a statistical analysis plan. These details are not reported in the registry record, so the posted results cannot resolve questions about prespecification, analysis choices, or the effect of missing information.

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 registry reports zero serious adverse events and zero other adverse events in each posted safety group. It also reports zero deaths in each group. The listed numbers at risk for these summaries are 62 for vaginal misoprostol and 59 for intravenous oxytocin. No serious-event terms are listed.

These figures describe what was recorded in the registry. They should not be read as proof that no adverse events of any kind occurred, or as proof that the interventions have identical safety profiles. A zero count in a posted category means no event was recorded for that category in the reported data; it does not establish the absence of unrecorded, unmeasured, or otherwise unreported events. The record does not provide further detail about the method or duration of safety surveillance, definitions used for event categories, or how events were collected.

The adverse-event summary is separate from the secondary outcome concerning excessive uterine activity necessitating treatment. That outcome is reported as a participant count in the secondary results, whereas the safety figures use the registry's serious and other adverse-event categories. These should not be conflated. The available safety information is limited to the posted counts and does not support a broader comparative safety conclusion.

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

The primary result describes the observed time from medication initiation to vaginal delivery among the groups summarized in the registry. The median was 800 minutes in the vaginal misoprostol group and 693 minutes in the intravenous oxytocin group. The reported Wilcoxon comparison had p = 0.11. Taken together, these figures describe the recorded data and the sponsor's reported rank-based test; they do not establish that the groups are equivalent or that a difference of any particular size is present.

The p-value does not measure clinical importance. A result that does not meet a conventional significance threshold can still be compatible with a range of potentially relevant differences, particularly when a confidence interval for the contrast is not reported. Conversely, a numerical difference between medians is not, by itself, evidence that a real or clinically important group difference exists. Interpretation needs estimates of uncertainty and a clear understanding of the outcome and population.

The result applies to the stated comparison in multiparous women presenting at term for labor induction. It does not automatically apply to other populations, settings, or treatment regimens. The registry describes particular dosing approaches, but does not report all eligibility criteria, participant characteristics, or care procedures needed to judge how closely another setting might match the study.

The primary endpoint is a timing measure, not a complete assessment of maternal or neonatal outcomes. The listed secondary outcomes cover some of those other domains, but results are not available for all of them in the registry record. The posted safety counts are also limited summaries and do not establish absence of risk. Consequently, the primary result should not be treated as a stand-alone summary of all possible benefits and harms.

As a general statistical principle, absence of strong evidence for a difference is not evidence that the treatments are interchangeable. Demonstrating equivalence or non-inferiority requires a suitable design, a prespecified margin, and an analysis that addresses that question. Such a margin and analysis are not reported in the registry record. The posted superiority comparison therefore answers a narrower question about evidence for a difference, not whether the two strategies meet an equivalence standard.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of why a group contrast should be read through both its descriptive summaries and its inferential analysis. The primary outcome is a duration, and the registry reports medians and inter-quartile ranges rather than relying on an average alone. That choice describes the center and spread of observed times without assuming that the distribution is symmetric.

The analysis also illustrates the limits of a p-value when an effect estimate and confidence interval are not reported for the primary comparison. The Wilcoxon test result gives evidence about the rank-based comparison under its assumptions, but it does not quantify the size or precision of a difference in minutes. A reader can see the group summaries, yet cannot use a primary interval estimate to assess the range of contrasts compatible with the study's data.

The parallel randomized design is important to the intended comparison, while the lack of masking and the absence of detail about allocation methods, missing data, and analysis populations constrain fuller appraisal. The record's distinctions between enrollment and outcome-summary group sizes also underscore the need to know which participants contributed to each analysis. The registry does not explain those details.

The secondary outcomes make clear that a clinical comparison may include multiple questions beyond its primary endpoint. In general, more outcome tests require care in distinguishing prespecified findings from chance patterns. Here, the registry does not report a multiplicity strategy or complete results for all listed secondary outcomes. The available record thus supports a focused statistical reading of the timing endpoint, but not a comprehensive conclusion across every maternal and neonatal outcome.

Finally, the planning illustrations associated with a secondary outcome show why observed effects should not be treated as stable design targets without qualification. Planning based on an observed effect is illustrative and depends on its assumptions; it is not observed power and does not reveal the original sample-size rationale. The registry record does not report that rationale. These features make the study useful for examining how design, reporting, precision, and multiplicity shape interpretation, rather than for reducing a complex comparison to a single yes-or-no conclusion.

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 are specific to the information recorded for this trial. The study is listed as having no masking, but the registry does not explain whether knowledge of group assignment could have influenced treatment decisions, timing records, or assessment of other outcomes. The sequence-generation and allocation-concealment methods are also not reported, which limits assessment of how the randomization was implemented.

The primary result includes group medians, inter-quartile ranges, and a Wilcoxon p-value, but no primary effect estimate with a confidence interval is reported. The record therefore does not directly quantify uncertainty around the between-group contrast in time. It also does not clarify how the stated timeframe of up to 24 hours was applied to participants without a vaginal delivery within that period, or how incomplete timing data were handled.

The registry lists enrollment as 130, while the primary outcome summaries show group sizes of 62 and 59. The record does not explain the relationship between these entries, identify an analysis population, or give participant flow information. It is not possible to determine from the record whether differences reflect exclusions, missing outcome data, or another reason.

The record describes medication regimens but does not give further details on clinical management or consistency of care across groups. It does not report participant characteristics that would help assess the balance or applicability of the study population. The listed condition and summary identify multiparous women presenting at term, but additional eligibility criteria are not reported in the registry record.

Finally, results are not posted for all listed secondary outcomes, and no multiplicity procedure, analysis plan, or sample-size justification is reported. These limitations do not prove that such procedures or information were absent from the study; they restrict what can be established from the registry record. The safety summary likewise consists of recorded counts and does not provide enough detail to characterize safety surveillance or events beyond those categories.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study Comparing Vaginal Misoprostol and Intravenous Oxytocin for Induction of Labor — NCT01634854.
• Registry record last updated 2017-12-19; status last verified 2017-11.
• Results first posted 2017-06-28.
• 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 randomized, parallel-group study with no masking comparing vaginal misoprostol with intravenous oxytocin for labor induction in multiparous women. The listed enrollment is 130. The primary endpoint is time from medication initiation to vaginal delivery, in minutes, with a timeframe of up to 24 hours.

The posted medians were 800 minutes for vaginal misoprostol and 693 minutes for intravenous oxytocin. The reported Wilcoxon (Mann-Whitney) comparison had p = 0.11. No primary confidence interval is reported in the registry record. The result does not meet the conventional 0.05 threshold and does not establish equivalence or a clinically important difference.

The record lists maternal and neonatal secondary outcomes, but does not report results for all of them. Safety summaries record zero serious adverse events, zero other adverse events, and zero deaths in each group. Details on missing data, analysis populations, multiplicity, and the statistical analysis plan are not reported in the registry record.