Safety and Expulsion of Delayed Versus Immediate Postpartum Intrauterine Device Placement: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Expulsion of Delayed Versus Immediate Postpartum Intrauterine Device Placement (NCT01598662), a randomized na study. The primary outcome is IUD Expulsion Rate.

2. Clinical Question

The registry summary says the investigators sought to compare expulsion and complication rates between the placement strategies. The primary outcome reported in the results is IUD expulsion, recorded as a count of participants. The comparison is difficult to interpret because the interval arm had no participants evaluated for this outcome, while only 2 participants in the immediate arm were evaluable. These follow-up limitations leave the central comparative question unresolved by the posted outcome data.

3. Trial Design

This was a randomized, controlled, parallel-arm trial with no masking. The registry record lists an enrollment of 32 and identifies the University of Louisville as sponsor. The record describes pregnant women who delivered vaginally at the University of Louisville Hospital and wanted an IUD for postpartum contraception. Participants who consented and were eligible were assigned to immediate post-placental placement or interval placement at six weeks postpartum or later.

The intervention was a Mirena levonorgestrel-releasing intrauterine system in both arms. For immediate placement, the intended timing was within 10 minutes of placental delivery. The arm description says placement was manual, sterile, and ultrasound-guided, with an ultrasound planned within two days post-placement. For interval placement, the IUD was to be placed in the office at six weeks postpartum or later, followed by a string-check visit within a month. The registry record does not report further details about how randomization was generated or concealed.

The primary outcome was IUD expulsion, with a stated timeframe of 6 months. The trial status is terminated. The record lists a start date of 2009-07 and a primary completion date of 2011-03-21. The registry record does not report why the trial was terminated or whether the planned enrollment was reached. It also does not report the trial's sample-size justification, a detailed statistical analysis plan, or any interim-analysis plan. The posted outcome data reflect a much smaller evaluable group than the overall enrollment, which is important when interpreting the comparison.

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: 0 participants were evaluable in the Arm "IUD Insertion 6 Weeks After Delivery", as 0 participants received an IUD at 6 weeks, and 2 participants in the Arm "Immediate Post-placental Insertion" were evaluable, as there were only 2 participants that came back for a follow up appointment.

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 IUD Expulsion Rate, measured over 6 months.

The primary endpoint is IUD expulsion, expressed as a count of participants with the event. The registry definition is based on clinical examination: expulsion is confirmed when the physician cannot visualize the string attached to the IUD coming from the cervix. The outcome timeframe is 6 months.

This endpoint was selected to address a practical concern about when to place an IUD after delivery. Immediate placement and interval placement occur at different postpartum times, so comparing expulsion can describe whether the timing strategies were associated with different observed counts in this trial. The endpoint is not a complete measure of every aspect of safety, acceptability, or contraceptive use; those broader outcomes are not reported as primary results in the registry record.

The result is reported as a count rather than as a complete comparative estimate. The interval arm had 0 evaluable participants because 0 participants received an IUD at six weeks. The immediate arm had 2 evaluable participants, and its posted endpoint value is 2. Without evaluable participants in the interval arm, the registry record does not supply a usable comparison of expulsion between the assigned strategies. The limited follow-up also means the recorded outcome cannot establish how expulsion would look across the full enrolled group.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization assigns participants to study groups by chance. In general, this approach is used to reduce systematic differences between groups at the start of a trial. This record identifies the study as randomized and parallel, but does not report the sequence-generation method or allocation-concealment procedure. It also lists masking as none. These design labels describe the intended assignment structure; they do not ensure that outcomes were observed for all randomized participants.

What does a count endpoint show?

A binary outcome records whether each participant experienced an event or did not. A count of participants with the event summarizes the observed event cases in a group. For a comparison, that count needs to be interpreted with the number of participants whose outcomes were assessed. The record identifies the primary outcome as a count of participants, and describes expulsion through inability to visualize the IUD string at the cervix. It reports 0 evaluable participants in the interval arm and 2 in the immediate arm. With no evaluable interval participants, the registry record cannot provide a complete comparison of event frequency between arms.

Why do denominators matter?

A count alone does not communicate how commonly an event occurred unless the relevant outcome-assessed population is also known. Even when the assessed population is reported, small groups give limited information about the range of results that might be compatible with the data. A confidence interval is a statistical range used to express uncertainty around an estimate; a narrow interval generally indicates greater precision, while a wide interval indicates less precision. No comparative confidence interval is reported for this endpoint, and the lack of an evaluable interval group prevents a useful arm-to-arm estimate from the posted results.

What does non-estimable mean?

For a binary outcome, a comparison may be non-estimable when the available data do not support calculation of a valid contrast between groups. Here, the record specifically indicates that values are missing or not estimable for a two-arm binary-endpoint comparison. This is consistent with the reported absence of evaluable participants in the interval arm. It does not mean that the groups were shown to be equivalent, and it does not establish that any observed difference is absent. It means the registry record does not contain the information needed to quantify the comparison.

How should statistical significance and power be understood?

A significance test evaluates how compatible observed data are with a specified statistical model and null hypothesis. A p-value, when reported, is not the probability that a treatment works or that the null hypothesis is true. No p-value or inferential test result is reported for the primary comparison. The record's planning description refers to a two-sided significance level of 0.05, equal allocation, and a normal approximation, but does not give planning sample-size values in the information available for this trial. Such planning illustrations are not observed power. Power is a design concept, and it cannot turn sparse follow-up into evidence of no difference.

In general, over-dispersion means that observed variability exceeds what a chosen statistical model expects. It can matter when a model assumes less variability than the data exhibit, because standard errors and uncertainty estimates may then be too small. The primary outcome is a binary participant count, and the registry record does not report a model-based analysis or an over-dispersion assessment. No conclusion about such an assessment should be inferred.

The record lists no analyses and does not report a comparative estimate, confidence interval, or p-value. There are no recalculated comparisons described for this endpoint. If recalculated summary-statistic results were available, they would represent simple unadjusted calculations rather than the sponsor's own analysis; however, the record does not provide such a comparison. No sponsor analysis is reported that could take precedence over a recalculation.

The sample-size description characterizes planning illustrations based on fractions of the observed effect. It also states the assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation. No numeric planning results are reported in the registry record. A planning illustration is not a statement about the trial's achieved power, and it is not evidence that the observed data can support a precise conclusion.

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("Immediate Post-placental Insertion")
n      <- c(2)
events <- c(2)
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  Immediate Post-placental Insertion  2  2  100.0  15.8  100.0  34.2  100.0  29.2  99.2

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure and no secondary outcomes. It lists no analyses. Because no set of inferential tests or secondary results is reported, the record does not describe a multiplicity adjustment or explain how multiple comparisons would have been handled. Whether such procedures were planned is not reported in the registry record.

Missing outcome information is central to interpreting the primary comparison. The record says that 0 participants were evaluable in the interval arm because 0 participants received an IUD at six weeks. In the immediate arm, 2 participants were evaluable because only 2 returned for a follow-up appointment. The overall enrollment was 32, but the primary outcome data do not cover the enrolled group comparably across arms. The registry record does not report reasons for all missing outcomes or describe methods for handling missing data.

The record does not describe an intention-to-treat analysis, a per-protocol analysis, or another analysis population beyond the evaluable counts in the outcome description. It does not state how participants who did not receive their assigned placement or did not return for follow-up were handled analytically. These details are important because an analysis restricted to observed participants can differ from one that follows the original randomized assignments, especially when outcome availability is limited.

There is no basis in the registry record for assuming that missingness was random or that missing participants would have had outcomes like those who returned. No imputation strategy, sensitivity analysis, or missing-data assumption is reported. The available counts should therefore be interpreted as the posted observations, not as complete outcomes for all randomized participants.

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 record reports serious adverse events, other adverse events, and deaths separately for the two arms. In the interval-placement group, 11 participants were listed as at risk for serious events and 11 for other events; the recorded counts were 0 serious events, 0 other events, and 0 deaths. In the immediate-placement group, 21 participants were listed as at risk for serious events and 21 for other events; the recorded counts were 0 serious events, 0 other events, and 0 deaths.

These are recorded event counts, not a guarantee that no adverse events occurred outside the registry's reporting. The numbers at risk for these safety summaries are distinct from the primary-endpoint evaluable counts. In particular, they should not be substituted for the expulsion follow-up populations, which the registry describes as 0 in the interval arm and 2 in the immediate arm.

Zero recorded events in a group does not by itself establish that the underlying risk is zero. The counts must be read in light of the number at risk and the completeness of reporting. The registry record does not provide further detail about event definitions, severity grading beyond the serious-versus-other distinction, or the methods used to collect adverse-event information.

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

The posted results establish what the registry records: the trial was randomized, enrolled 32 participants, and reported a primary outcome of IUD expulsion. For that outcome, the interval-placement arm had 0 evaluable participants because 0 received an IUD at six weeks; the immediate-placement arm had 2 evaluable participants and an endpoint count of 2. The record also reports zero serious adverse events, zero other adverse events, and zero deaths in each arm's safety summary.

These results do not establish a comparative expulsion rate. The interval arm has no evaluable primary-outcome participants, and the immediate arm has only 2. There is no reported comparative estimate or uncertainty interval to indicate how precise a difference might be. The results also do not establish that the two placement strategies are equivalent, that one is superior, or that either has a particular effect on expulsion.

The safety counts are informative as registry entries, but they do not provide a comprehensive account of safety beyond the recorded categories and participants at risk. They cannot substitute for the primary endpoint comparison, and the record does not provide detail sufficient to assess unreported events or the completeness of ascertainment.

More broadly, this is a description of the evidence captured in the registry record, not a recommendation about postpartum contraception or IUD placement. The record's termination status and limited primary-outcome follow-up constrain what can be learned from the posted results. The intended clinical question remains unanswered by the available comparative data.

14. Why This Trial Matters Statistically

This trial illustrates that randomization and outcome follow-up answer different statistical questions. Randomization establishes an assignment framework intended to support a fair comparison. To estimate an outcome contrast, however, results must also be available for participants in the groups being compared. Here, the registry reports no evaluable participants in the interval arm and 2 in the immediate arm for the primary outcome. Consequently, the randomized design does not yield a usable posted comparison of expulsion.

The trial also demonstrates why enrollment should not be mistaken for the number contributing to a particular endpoint. The record lists enrollment of 32, but the primary-outcome description gives a much smaller evaluable population. Readers need to distinguish the overall enrollment from the outcome-specific denominator and to consider whether follow-up is represented in both arms.

From a statistical perspective, a count without a functioning comparator cannot answer the central comparative question. A missing estimate is not evidence of no difference, and a sparse observed count should not be treated as precise merely because it is stated exactly. Precision depends on the amount and distribution of outcome information, as well as the analysis method.

The record is also a reminder to separate safety summaries from efficacy or performance endpoints. The recorded adverse-event counts and the expulsion endpoint concern different outcomes and use different reported populations. Each needs to be read with its own denominator and follow-up context.

These issues matter in clinical-trial reporting because clear outcome definitions, complete follow-up, and transparent analysis methods are needed for readers to evaluate what the data can support. In this record, the endpoint definition is stated, but comparative estimation, missing-data methods, and detailed analysis procedures are not reported.

15. Limitations

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

The main trial-specific limitation is the very limited evaluable population for the primary outcome. The interval arm had 0 participants who received an IUD at six weeks and 0 participants evaluable. The immediate arm had only 2 participants returning for follow-up. This prevents a meaningful comparison of expulsion between the assigned strategies and limits interpretation of the posted endpoint count.

The trial is listed as terminated, but the reason for termination is not reported in the registry record. The record lists enrollment of 32; it does not explain why so few participants contributed to the primary outcome or whether the planned enrollment was achieved. The registry record also does not report a sample-size justification, detailed randomization procedures, allocation concealment, or a complete statistical analysis plan.

Important analysis details are absent. The record does not describe how missing primary outcomes were handled, whether the analyses followed randomized assignment, or whether sensitivity analyses were performed. It does not report a comparative estimate, confidence interval, or p-value. No secondary outcomes or analyses are listed. The stated outcome timeframe is 6 months, but the outcome description does not establish complete follow-up through that timeframe for the evaluable participants.

Safety information is limited to the recorded counts of serious events, other events, and deaths, with the listed numbers at risk. Further definitions and ascertainment details are not reported. These limitations mean the registry record can describe the reported counts and study structure, but cannot support a precise conclusion about comparative expulsion or provide a complete assessment of safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety and Expulsion of Delayed Versus Immediate Postpartum Intrauterine Device Placement — NCT01598662.
• Registry record last updated 2018-09-25; status last verified 2018-08.
• Results first posted 2018-07-26.
• 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.

19. Record Summary

NCT01598662 is a randomized, controlled, parallel-arm trial of immediate post-placental versus interval Mirena placement after vaginal delivery. The record lists no masking, enrollment of 32, University of Louisville sponsorship, and a terminated status. It gives a start date of 2009-07 and a primary completion date of 2011-03-21.

The primary endpoint was IUD expulsion over 6 months, defined by inability to visualize the IUD string coming from the cervix. The interval arm had 0 evaluable participants because 0 received an IUD at six weeks. The immediate arm had 2 evaluable participants and a posted endpoint count of 2. No comparative analysis is reported, and the binary comparison is identified as not estimable from the available data.

The safety record lists 0 serious adverse events, 0 other adverse events, and 0 deaths in both arms. The registry record does not report the reason for termination, a sample-size justification, missing-data methods, or a detailed analysis plan. The limited primary-outcome follow-up leaves the intended comparison unresolved.