Cervical Ripening for Induction of Labor: Misoprostol Versus Oxytocin in Conjunction With Foley Balloon: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cervical Ripening for Induction of Labor: Misoprostol Versus Oxytocin in Conjunction With Foley Balloon (NCT01139801), a randomized na study. The primary outcome is Rate of Induction To Delivery.

2. Clinical Question

This question is specific to the study’s treatment combinations and outcome definition. It does not, by itself, address other induction regimens, other populations, or outcomes beyond those registered. The record identifies a randomized, parallel-group comparison with no masking. It reports a total enrollment of 50, while the primary outcome results include 16.0 participants in the oxytocin arm and 17.0 in the misoprostol arm. The record says patients requiring caesarean section were excluded from the primary analysis, but it does not report why the number analyzed differs from total enrollment or provide further details about those excluded.

3. Trial Design

The registry describes a randomized, parallel-group trial of misoprostol versus oxytocin, both used in conjunction with a Foley balloon. The study is marked completed and lists enrollment of 50. The sponsor is Aultman Health Foundation. The phase field is recorded as NA. The study began in 2009-09, and primary completion is listed as 2010-03.

Randomization means the study assigned participants to one of the treatment groups according to a randomized process. The record does not describe the sequence-generation method, allocation concealment, or whether group assignment was balanced in practice. The trial is listed as having no masking, so it was not a masked comparison according to the registry entry. The record does not say which parties knew the assigned treatment or describe any measures to limit bias in outcome assessment.

The two arms differed in the drug regimen while both included Foley balloon placement. In the oxytocin arm, the registry describes intravenous low-dose oxytocin beginning at 2 milliunits per minute. In the misoprostol arm, it describes 25 mcg placed intravaginally into the posterior fornix. More detail about dose adjustment, timing, repeat administration, balloon management, or other co-interventions is not reported in the registry record.

The primary outcome was a continuous measure: mean rate of induction to delivery, expressed in minutes, with a 24 hrs timeframe. The primary analysis population excluded patients requiring caesarean section. The results list 16.0 participants for oxytocin and 17.0 for misoprostol. Delivery route appears as a secondary outcome, but its results are not reported in the registry record. The registry lists two outcome measures and one analysis; further detail on the full analysis plan, the original sample-size justification, and the handling of missing outcome data is not reported.

4. Participant Flow and Accounting

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

Overall Study

Analysis population for the primary outcome, as defined in the registry: Patients requiring caesarean section excluded from analysis.

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 Rate of Induction To Delivery, measured over 24 hrs.

The primary endpoint, Rate of Induction To Delivery, measures the elapsed time from induction to delivery in minutes. The registry gives a timeframe of 24 hrs and describes the purpose as assessing induction times with misoprostol plus Foley balloon compared with the standard oxytocin regimen plus Foley balloon. The reported endpoint is a mean, a summary of the average time in each analyzed group.

Time to delivery is relevant to this comparison because the study is evaluating two cervical-ripening regimens as part of labor induction. A continuous time measure retains information about the duration recorded for each participant, rather than reducing the result to a yes-or-no outcome. The mean difference expresses how far apart the group averages are, while uncertainty measures help show how precisely that difference is estimated.

The registry states that patients requiring caesarean section were excluded from the primary analysis. The displayed primary results therefore describe the analyzed participants under that exclusion, not every person enrolled. The number of participants excluded for this reason, their outcomes, and the detailed definition of the start and end points used to calculate induction-to-delivery time are not reported in the registry record. These details matter when interpreting what the endpoint represents and how broadly the estimate applies.

7. Results Posted in the Registry

• Misoprostol: mean 944.35 versus 732.19 on control; difference 212.16 (95% CI 21.62 to 402.70), standardized effect d = 0.75; z-test p = 0.029.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is continuous: induction-to-delivery time in minutes, summarized by a mean and standard deviation for each arm. The reported group means are 732.2 for oxytocin and 944.4 for misoprostol. The standard deviations are 237.0 and 317.8, respectively. A standard deviation describes the spread of individual observations around a group mean; it is not the uncertainty in the estimated mean itself. The registry lists 16.0 and 17.0 participants in the outcome groups.

What does the mean difference represent?

The posted mean difference is 212.2 minutes, calculated in the direction misoprostol minus oxytocin. A difference in means compares the average outcome between groups while retaining the original unit, minutes. The sign depends on the order of subtraction, so the direction should be read together with the stated arm order. This contrast compares misoprostol with oxytocin when each is used with a Foley balloon; it does not isolate either drug from the shared procedure.

Why use a two-sided t-test?

The registry reports a two-sided t-test for the mean difference. In general, a t-test evaluates whether the data are compatible with a specified mean difference, commonly zero, while accounting for sampling variability. A two-sided test considers departures in either direction. Its p-value is not a measure of the probability that a treatment effect is real, nor does it express the size of the difference. The registry reports p = 0.037. The unadjusted recalculation from the posted summary statistics reports p = 0.029. These are results from the respective analyses, not values to combine.

General explanation: a t-based interval uses an estimate and its standard error to describe uncertainty in the mean difference. A standard error reflects the precision of an estimate and depends on the variability of observations and the amount of information available. Greater variability or less information generally makes an estimate less precise. In this trial, the group standard deviations and sample sizes are reported, but no participant-level data or further modeling details are available in the registry record.

How should the confidence interval be read?

The registry’s 95% confidence interval for the mean difference runs from 13.3 to 411.0 minutes. The unadjusted recalculation gives a 95% confidence interval from 21.62 to 402.7 minutes. In general, a confidence interval is a range produced by a method that, under repeated use and its assumptions, would cover the true parameter at the stated rate. For an individual trial, it is best read as a range of estimates compatible with the data and method, rather than as a probability statement about where the fixed true value lies. The width conveys precision: wider intervals indicate greater uncertainty about the effect’s size.

The interval reported by the registry and the recalculated interval are not identical, although both are centered on the posted mean difference of 212.2 minutes. The record specifies the sponsor analysis as a two-sided t-test on final values, but does not provide enough detail to identify why the intervals differ from the unadjusted recalculation. The p-values also differ. Each result should therefore remain attached to the analysis that generated it.

What does variability mean in this setting?

General explanation: a mean can hide variation among participants. Two groups may have different averages while individual outcomes overlap substantially. The standard deviation helps describe this spread, whereas the confidence interval focuses on uncertainty in the group contrast. These quantities answer related but different questions. The registry reports a standard deviation of 237.0 for oxytocin and 317.8 for misoprostol, with corresponding standard errors of 59.25 and 77.07 in the recalculation. The latter describe uncertainty in each group mean, not the range of individual delivery times.

General explanation: unusually variable or skewed data can affect how well a simple mean-based model represents the observations. A small sample can also make estimates sensitive to individual observations. The registry record does not report a distributional assessment, a robust or transformed analysis, or a sensitivity analysis. It is therefore not possible to determine from the record whether these issues were evaluated.

What is and is not established by the analysis?

The recalculation is an unadjusted comparison based on posted summary statistics. It does not add covariate adjustment, account for unreported design features, or replace the trial’s own analysis. The record identifies randomization but does not describe the randomization procedure, allocation concealment, or any adjustment strategy. It also does not report a formal sample-size justification, interim analyses, or a detailed statistical analysis plan. The only reported analysis is the two-sided t-test on final values.

General explanation: random assignment can help balance measured and unmeasured characteristics across groups in expectation, but the details of implementation and the realized group composition still matter. Here, no baseline characteristics are included in the outcome information. Further, the primary analysis excluded patients requiring caesarean section. Without a reported count and explanation for those exclusions, the potential effect of that restriction cannot be assessed from the record. These limitations concern the interpretation and precision of the estimate, not a recalculation of the posted result.

10. Confidence Intervals and Precision

The registry reports a mean difference of 212.2 minutes, with a 95% confidence interval from 13.3 to 411.0. The unadjusted recalculation gives the same point estimate, 212.2 minutes, with a 95% confidence interval from 21.62 to 402.7. The intervals are not identical, so the precision should be described with the analysis attached: the first is the registry’s reported analysis, and the second is the recalculation from posted summary statistics.

In general, a confidence interval represents uncertainty about the estimated difference under the assumptions of the method. Its endpoints indicate a range of values compatible with the data and analysis; they are not a guarantee that the true difference lies within that particular interval. Both intervals are entirely above zero, while their spans indicate that the magnitude remains uncertain. The estimates are consistent with a positive difference, but the possible size of that difference is not pinned down narrowly.

The reported group standard deviations are 237.0 minutes for oxytocin and 317.8 minutes for misoprostol. The outcome sample counts are 16.0 and 17.0. These group sizes are modest, and the record states that patients requiring caesarean section were excluded from the primary analysis. The number excluded is not reported in the registry record. That missing information limits assessment of how the analyzed sample relates to total enrollment of 50.

Confidence intervals address sampling uncertainty under a method; they do not capture every source of uncertainty. They do not, on their own, address possible bias from exclusions, trial conduct, outcome measurement, or unreported analytic choices. The registry’s analysis and the recalculation differ in interval width and p-value, and the record does not explain the difference. For interpretation, the interval should be considered alongside the endpoint definition, the analyzed population, and the limits of the registry’s methodological detail.

11. Planning a Similar Trial: Sample Size

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

The planning figures are participants per arm, not total events. They are illustrations based on the observed mean difference, not the original trial’s documented design assumptions. The registry record does not report the trial’s own sample-size justification or its original assumptions.

The planning illustration uses a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It considers effects equal to 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For each assumed effect, the 80% power column gives the number of participants per arm under the stated assumptions to provide an 80% chance of detecting that effect if it were the true effect and the model assumptions held. The 90% power column gives the corresponding per-arm planning number for a 90% chance under those assumptions.

For planning at 100% of the observed effect, the figures are 28 participants per arm for 80% power and 38 for 90% power. For planning at 75% of the observed effect, they are 50 and 66 participants per arm. For planning at 50% of the observed effect, they are 111 and 149 participants per arm. The pattern reflects a general statistical principle: smaller effects are harder to distinguish from random variation, so detecting them at the same power generally requires more participants.

These are prospective planning illustrations calculated from the observed effect, not evidence about the probability that the completed trial detected a true effect. This is not observed power. They also should not be read as the planned size of this trial: the trial enrolled 50, and its original design justification is not reported in the registry record. The figures depend on the stated assumptions, including equal allocation and the normal approximation, and should be interpreted as conditional planning examples rather than a reconstruction of the study’s design process.

12. How the Sample Size Is Derived

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

Formula

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

Worked calculation for this trial

1. Observed difference Δ = 212.160; pooled standard deviation σ = 281.597.
2. n = 2 × (1.96 + 0.842)² × 281.597² / 212.160² = 27.7, rounded up to 28 participants per arm for 80% power.

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

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 212.16                      # observed difference in means
sigma <- 281.597399404918                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

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

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1139801)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 28 (80% power), 38 (90% power)
 75% of observed effect: n per arm = 50 (80% power), 66 (90% power)
 50% of observed effect: n per arm = 111 (80% power), 149 (90% power)
power.t.test: 28.6 
Simulated power at n = 28 per arm: 0.796 (20000 replicates)

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

13. Analyses Reported by the Sponsor

The registry’s own analysis reports a two-sided t-test of the mean difference in final values. It gives a mean difference of 212.2 minutes, a 95% confidence interval from 13.3 to 411.0, and p = 0.037. The unadjusted recalculation from the posted group means, standard deviations, and sample sizes gives the same mean difference of 212.2 minutes, with a 95% confidence interval from 21.62 to 402.7 and p = 0.029.

The point estimates agree, while the confidence intervals and p-values differ. These estimates should not be averaged or treated as interchangeable: each belongs to its own calculation. The registry identifies its analysis method as a two-sided t-test, but the record does not provide enough detail to explain why its uncertainty estimates differ from the recalculation. The recalculation is unadjusted and uses the posted summary statistics; it does not supersede the registry’s reported analysis. The record does not flag a discrepancy.

Both analyses indicate a positive estimated mean difference in the stated direction. Their differing uncertainty measures are a reminder that analytic details can matter even when the point estimate is the same. The registry’s own result remains the reported trial analysis, while the recalculation offers a transparent comparison based on the available group summaries. Neither analysis resolves limitations from the small analyzed groups, the exclusion of patients requiring caesarean section, or unreported details of the analysis population.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and one analysis. The primary endpoint is mean induction-to-delivery time, and delivery route is listed as a secondary outcome. Results for the secondary outcome are not reported in the registry record. The record does not describe whether there were additional outcomes that were measured but not posted.

Multiplicity arises when several hypotheses or outcomes are tested: the more comparisons considered, the greater the chance of finding a nominally unusual result by chance if no effects are present. General explanation: a prespecified primary outcome and analysis can help clarify which result is the principal confirmatory comparison, while adjustment methods may be used when many tests are interpreted together. The registry record does not report a multiplicity adjustment or explain how multiple outcomes were handled. The record’s single listed analysis does not establish that no other analyses were conducted.

The record does not report interim analyses, stopping rules, or a detailed statistical analysis plan. It also does not report the original sample-size justification. These omissions mean that readers cannot assess from the registry entry whether the reported endpoint, analysis population, and test were specified before the results were known, or whether any other analyses influenced interpretation.

Missing-data handling is not described. The registry states that patients requiring caesarean section were excluded from the primary analysis, but does not report how many participants were excluded, the timing or reasons for any other missing measurements, or whether any imputation or sensitivity analysis was used. The primary outcome results include 16.0 participants for oxytocin and 17.0 for misoprostol, while total enrollment is 50. The record does not reconcile those counts. Without that information, it is not possible to determine how the analysis sample was formed or whether exclusions could affect the estimated contrast.

Randomization is reported, but the analysis population and allocation details are not fully described. The record does not report an intention-to-treat analysis, a per-protocol definition, or an adjusted analysis. These omissions should not be filled in by assumption. They limit assessment of multiplicity, missingness, and the population to which the primary estimate applies.

15. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The registry reports serious adverse events for 25 participants at risk in each group, with zero serious adverse events affecting participants in the oxytocin group and zero in the misoprostol group. It also reports 25 participants at risk in each group for other adverse events, with zero affected in either group. Deaths are reported as zero in both groups. No serious adverse event terms are listed.

These figures describe what is posted in the registry and should be read with the stated at-risk counts. They do not show that the risk of an adverse event is absent; zero recorded events in a study of this size leaves uncertainty about uncommon outcomes. General explanation: safety estimates are especially imprecise when few participants are observed, and a registry summary cannot establish that all events were detected or reported.

The record does not provide additional detail about event definitions, collection procedures, severity grading, follow-up duration, or whether adverse events were assessed in the same population as the primary outcome. It also does not report individual event narratives. The numbers therefore summarize the recorded safety counts but do not support conclusions beyond those counts.

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

The posted primary results describe mean induction-to-delivery times among participants included in the analysis after excluding patients requiring caesarean section. The mean was 732.2 minutes in the oxytocin group and 944.4 minutes in the misoprostol group. The reported mean difference, defined as misoprostol minus oxytocin, was 212.2 minutes. The registry’s own analysis reports a 95% confidence interval from 13.3 to 411.0 and p = 0.037; the unadjusted recalculation gives a 95% confidence interval from 21.62 to 402.7 and p = 0.029.

These findings describe a difference in the observed group averages for the specific regimens studied. Both arms included a Foley balloon, so the result is not a comparison of the drugs without that shared procedure. The endpoint is induction-to-delivery time in minutes, not delivery route or another measure of labor outcome. Although delivery route is listed as a secondary outcome, its results are not reported in the registry record.

The result does not establish the size of a true underlying effect with high precision. Both confidence intervals cover a range of positive values, and the reported groups are small. The record also states that patients requiring caesarean section were excluded, without giving the number excluded or the outcomes for those patients. Total enrollment was 50, while the primary results include 16.0 and 17.0 participants by arm; the record does not explain the difference.

A p-value below 0.05 does not establish that an effect is clinically important, nor does it prove a causal explanation beyond the randomized comparison as reported. General explanation: statistical evidence and clinical relevance are different questions. The registry does not define a threshold for a meaningful difference in minutes, and it does not report broader maternal or neonatal outcomes in these results. The findings therefore should not be extended to unreported outcomes, other populations, or treatment choices. They are a record of the primary endpoint estimate and its uncertainty for the analyzed participants.

17. Why This Trial Matters Statistically

This study illustrates why a treatment comparison needs to be read through its endpoint, analysis population, and uncertainty rather than through a single p-value. The primary outcome is a continuous time measure, and the registry reports both group means and a mean difference in minutes. That keeps the estimated contrast interpretable in the endpoint’s original unit. The confidence intervals then show that the estimate is not a single fixed value known without uncertainty.

It also illustrates the importance of identifying what is actually being compared. Misoprostol and oxytocin were each used with a Foley balloon, so the trial addresses two combined regimens. The result cannot isolate the effect of the drug from the shared procedure. The primary analysis also excluded patients requiring caesarean section. Without the number excluded and their outcomes, readers cannot fully judge how that restriction shaped the analyzed population.

The registry’s own analysis and the unadjusted recalculation agree on the point estimate but give different confidence intervals and p-values. That is a useful reminder that reported estimates depend on the analysis used, not just the group means. The record does not give enough methodological detail to explain those differences, nor does it report a complete statistical analysis plan. Keeping the registry result distinct from the recalculation preserves that distinction.

Finally, the sample-size illustration links effect size to the amount of information needed for planning: smaller assumed effects require more participants to achieve the same stated power. These planning figures are not a retrospective measure of whether the completed trial was adequately powered, and they do not document the trial’s original design. The combination of a modest analyzed sample, incomplete information about exclusions, and unreported secondary results makes careful scope and precision central to interpreting the record.

18. Limitations

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

The primary endpoint results include 16.0 participants in the oxytocin group and 17.0 in the misoprostol group, while total enrollment is 50. The registry states that patients requiring caesarean section were excluded from the primary analysis, but does not report the number excluded or reconcile the analysis counts with enrollment. This leaves uncertainty about how the analysis population was selected and how the exclusion may affect interpretation.

The record gives limited detail about trial conduct. It identifies randomization and no masking, but does not describe how the random sequence was generated, how allocation was concealed, or which people knew treatment assignments. It does not report baseline characteristics, the definition of the time origin for induction, or other details needed to assess comparability and measurement. Further dosing and co-intervention details are not reported in the registry record.

The registry lists delivery route as a secondary outcome, but results for it are not reported. It also does not provide a detailed statistical analysis plan, multiplicity approach, interim analysis information, or the original sample-size justification. Missing-data methods and sensitivity analyses are not reported. These gaps limit evaluation of whether the posted comparison reflects the complete prespecified analysis and how robust it is to analytic choices.

The trial’s own analysis reports a t-test result, whereas the unadjusted recalculation based on summary statistics produces different interval limits and a different p-value. The record does not explain this difference. The reported outcome is also specific to mean induction-to-delivery time among the analyzed participants; it cannot answer questions about unreported endpoints or outcomes beyond that population. Finally, the event counts posted for safety are zero in both arms, but the registry does not provide further detail on ascertainment, definitions, or follow-up. These limitations warrant restraint in interpreting the scope and precision of the results.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Cervical Ripening for Induction of Labor: Misoprostol Versus Oxytocin in Conjunction With Foley Balloon — NCT01139801.
• Registry record last updated 2018-08-24; status last verified 2018-08.
• Results first posted 2018-08-24.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

The registry describes a completed, randomized, parallel-group study comparing misoprostol with oxytocin, with both regimens used alongside a Foley balloon. Enrollment was 50, and the sponsor was Aultman Health Foundation. The primary endpoint was mean induction-to-delivery time in minutes, with patients requiring caesarean section excluded from that analysis.

The posted means were 732.2 minutes for oxytocin and 944.4 minutes for misoprostol. The registry’s analysis reports a mean difference of 212.2 minutes, a 95% confidence interval from 13.3 to 411.0, and p = 0.037. The unadjusted recalculation reports a 95% confidence interval from 21.62 to 402.7 and p = 0.029. The primary results include 16.0 and 17.0 participants by arm.

Delivery route is listed as a secondary outcome, but its results are not reported in the registry record. Serious adverse events, other adverse events, and deaths are recorded as zero in both groups. The record does not report the original sample-size justification, detailed missing-data methods, or further explanation of the difference between the reported analysis and the recalculation.