A Study to Evaluate the Effectiveness of Essure Post-NovaSure Radiofrequency Endometrial Ablation Procedure Following a Successful Essure Confirmation Test: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Evaluate the Effectiveness of Essure Post-NovaSure Radiofrequency Endometrial Ablation Procedure Following a Successful Essure Confirmation Test (NCT01740687), a registered phase not stated study. The primary outcome is Number of Pregnancies at 1-year Time Point (1-year Pregnancy Rate).

2. Clinical Question

In plain terms, the study was intended to assess effectiveness and safety when the two procedures occurred in this specified sequence. Its primary measure is a count at a stated follow-up point, rather than a reported comparison between treatment groups. Without the recorded pregnancy result, the endpoint's observed magnitude and precision cannot be described. The registry record also does not report details needed to assess how the enrolled group was selected or whether all enrolled participants contributed to the primary endpoint.

3. Trial Design

This was a post-approval study intended to evaluate the effectiveness and safety of the Essure System when NovaSure endometrial ablation was performed following a successful Essure Confirmation Test. The record lists Bayer as the sponsor and describes one group: women relying on Essure micro-inserts for permanent birth control when NovaSure was performed after successful confirmation. Enrollment was 211.

The registry record marks the study as completed. Its start date is 2012-11-13, and its primary completion date is 2021-05-17. The listed device is ESS305 (Essure, BAY1454032), and the listed procedure is NovaSure. The recorded primary endpoint is the number of pregnancies at 1 year after NovaSure endometrial ablation. A listed secondary outcome concerns the number of adverse events when NovaSure was performed in the presence of Essure inserts.

No comparator group is described, and allocation is not stated. The record explicitly cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. Consequently, the design information does not support interpreting the study as a randomized estimate of the difference between two treatment strategies. The registry record does not report further design details such as eligibility criteria, recruitment procedures, or a more detailed follow-up schedule.

The registry record lists three outcome measures and two analyses, but does not report the details of those analyses in the registry record for this account. It also does not report the statistical plan, sample-size justification, or whether interim analyses were planned. The stated post-approval purpose describes the study's broad aim; it does not by itself establish how participants were selected, how outcomes were ascertained, or how missing observations were handled.

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: A total of 220 participants were screened, of whom 215 participants met all the eligibility criteria at screening. NovaSure procedure was initiated for 211 participants, and 4 participants exited the study before the NovaSure attempt. Two participants for whom the procedure was initiated had the NovaSure procedure terminated before any energy was applied, thus 209 subjects underwent treatment with NovaSure. EA=Endometrial ablation.

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 Number of Pregnancies at 1-year Time Point (1-year Pregnancy Rate), measured over 1 year after NovaSure Endometrial Ablation procedure.

The primary endpoint is the number of pregnancies at the 1-year time point, defined in the record as 1 year after the NovaSure endometrial ablation procedure. It is a count outcome: it records how many pregnancies were observed by the specified follow-up point. The registry record gives the endpoint's unit as pregnancy and its parameter as a number.

This endpoint was selected to address the study's stated effectiveness question in a group relying on Essure micro-inserts for permanent birth control after a successful Essure Confirmation Test and subsequent NovaSure procedure. A pregnancy count can communicate whether any pregnancies were recorded during the stated period. To interpret it fully, however, readers also need to know how many participants had outcome information available, how pregnancy was identified, and how participants without complete follow-up were treated. Those details are not reported in the registry record.

The endpoint title also refers to a 1-year pregnancy rate, but the registry entries characterize the measure as a number. A count and a rate are not interchangeable: a rate requires a clearly defined denominator and, depending on its definition, may also require a specified observation period. The registry record does not report the pregnancy count, a calculated rate, or a confidence interval for either. No numerical conclusion about the endpoint's size or precision can therefore be drawn from the recorded results.

In general, a prespecified follow-up point helps define which events contribute to an endpoint. That definition does not resolve uncertainty caused by incomplete outcome ascertainment, and the relevant follow-up and missing-data procedures are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

For this study, the primary measure is a count of pregnancies at 1 year after NovaSure endometrial ablation. A count reports the number of recorded events, whereas a rate describes events relative to a defined denominator or time at risk. Although the endpoint title includes the phrase “pregnancy rate,” the registry record describes its parameter as a number and gives the unit as pregnancy. The registry record does not report the count or a rate estimate, so no numerical result can be interpreted.

What does a confidence interval describe?

In general, a confidence interval expresses the uncertainty around an estimate under a specified statistical model and analysis procedure. A narrower interval indicates greater precision under those assumptions; a wider interval indicates more uncertainty. An interval does not establish that an estimate is free of bias, and it cannot repair limitations in the design or outcome ascertainment. No confidence interval for the primary endpoint is reported in the registry record.

Why does the comparison structure matter?

In general, a comparison between groups is informative only when the groups and their assignment are described well enough to interpret the contrast. Random assignment can help balance factors that influence outcomes, while an observational or otherwise nonrandomized contrast may be affected by differences in who enters each group. The registry record does not state the allocation method and says the study is not a randomized comparison; it also cautions that the arms are not a like-for-like control comparison. No causal contrast should be inferred from those details.

The described study group consists of women relying on Essure micro-inserts when NovaSure was performed after a successful Essure Confirmation Test. A single described group can be characterized by its observed outcomes, but without an appropriate comparison it cannot establish how those outcomes differ from an alternative strategy. The primary pregnancy result is not reported in the registry record in any case.

How should the safety counts be read?

The registry record lists 211 participants at risk for serious adverse events and 18 affected; for other adverse events it lists 211 at risk and 95 affected. It also lists 1 death. These are descriptive counts, not comparisons of event risk between study groups. In general, event counts can differ from the number of people affected if participants experience more than one event, so readers need the registry's definition of “affected” and its event-counting rules to know precisely what is represented. Those details are not reported in the registry record. The record also does not report attribution of events to the device or procedure.

Several serious adverse event terms are listed with percentages: Pelvic pain, 2.4%; Heavy menstrual bleeding, 0.9%; Atrial fibrillation, 0.5%; Cardiac failure congestive, 0.5%; Torsade de pointes, 0.5%; and Abdominal pain upper, 0.5%. These are reported as listed. The registry record does not explain the denominator or whether participants could appear under more than one term, so the percentages should not be combined or treated as mutually exclusive.

What does a planning illustration mean?

In general, a sample-size calculation is a planning tool: it describes a hypothetical design's requirements under assumptions about the effect to detect, variability, significance level, allocation, and statistical method. It is not an observed result and is not “observed power.” The planning assumptions stated for this study use 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 stated fraction of the observed effect. For time-to-event outcomes, the stated illustration concerns the total number of events; for other outcomes, it concerns participants per arm.

These assumptions do not establish that the original study used that design. The record does not describe a randomized comparison, and only one group is described. The study's own sample-size justification is not reported in the registry record. No specific planning counts are reported in the registry record for interpretation, and no such count should be mistaken for the enrollment of 211 or for the number of observed outcomes.

What analysis details are needed?

The registry record lists three outcome measures and two analyses. In general, an analysis plan would clarify the target population, outcome definitions, follow-up rules, missing-data handling, and any adjustment or sensitivity analyses. Those details are not reported in the registry record. It is also not reported whether any interim analyses were planned or conducted. Without this information, readers cannot reproduce the primary analysis or evaluate whether the methods match the stated endpoint.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists three outcome measures and two analyses. When several outcomes or analyses are considered, the interpretation can depend on which question was designated primary, how other findings were treated, and whether any adjustment for multiple testing was planned. The record identifies the primary endpoint as the number of pregnancies at 1 year after NovaSure endometrial ablation and lists an adverse-event measure as secondary. The detailed analysis plan and any multiplicity procedure are not reported in the registry record.

Multiplicity is a general statistical concern: evaluating several questions can increase the chance that at least one result appears notable by chance, depending on the methods and interpretation. This concern cannot be quantified in the registry record recorded. The number of outcome measures and analyses does not reveal whether they were prespecified, whether they overlap, or which results were confirmatory versus exploratory.

The registry record does not report the number of participants with available primary endpoint data, the amount or pattern of missing data, or the method used to handle missing outcomes. It is also not reported whether participants with incomplete follow-up were excluded, retained under an imputation approach, or handled in another way. These omissions matter because incomplete follow-up can affect both the estimate and its precision, particularly for an outcome defined at a specific time point.

The analysis population is not reported in the registry record. Enrollment of 211 should not be assumed to equal the number analyzed for every outcome. The record also does not report a statistical analysis plan, interim analyses, or a sample-size justification. In general, these details help readers assess how analyses were selected and how robust conclusions are to decisions about data inclusion. Their absence limits assessment of the reported methods; it does not establish that any particular method was or was not used.

11. 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 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pelvic pain (2.4%), heavy menstrual bleeding (0.9%), atrial fibrillation (0.5%), cardiac failure congestive (0.5%), torsade de pointes (0.5%).

For the Essure + NovaSure group, the registry record lists 211 participants at risk for serious adverse events and 18 affected. For other adverse events, it lists 211 at risk and 95 affected. The record also lists 1 death. These figures describe the recorded group; they are not a randomized comparison of safety between alternative strategies.

The registry record lists these serious adverse event terms and percentages: Pelvic pain, 2.4%; Heavy menstrual bleeding, 0.9%; Atrial fibrillation, 0.5%; Cardiac failure congestive, 0.5%; Torsade de pointes, 0.5%; and Abdominal pain upper, 0.5%. The record does not state whether the terms refer to distinct participants, whether a participant could contribute to multiple terms, or how the percentages were calculated. It also does not report whether the events were considered related to Essure, NovaSure, or both.

In general, “at risk” and “affected” counts should be understood according to the registry's definitions and follow-up rules. Those definitions and the safety observation period are not reported in the registry record. The listed figures are descriptive and do not, on their own, establish causation or comparative safety.

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

The registry record documents a post-approval study intended to evaluate the effectiveness and safety of the Essure System when NovaSure endometrial ablation followed a successful Essure Confirmation Test. It records enrollment of 211 and identifies the primary endpoint as the number of pregnancies 1 year after NovaSure. However, the pregnancy result is not reported in the registry record. The stated study purpose and endpoint are not substitutes for an observed result.

The recorded safety information describes participants affected by serious and other adverse events and lists 1 death, along with selected serious adverse event terms and percentages. These figures can be read as descriptive registry entries. The record does not report event attribution, the safety follow-up period, or enough detail about event counting to support stronger conclusions about the source or pattern of events.

The registry record does not describe a randomized comparison and does not state allocation. It explicitly cautions that the arms are not a like-for-like control comparison. Thus, the design information does not establish a causal contrast between Essure plus NovaSure and another approach. A conclusion about comparative effectiveness or safety would require a suitable comparator and details about how the comparison was conducted.

In general, a study's result must be interpreted alongside its precision, analysis population, outcome ascertainment, and missing-data handling. The primary result, confidence interval, analysis population, and missing-data methods are not reported in the registry record. These omissions prevent assessment of the size and precision of the primary finding, rather than showing that the result was necessarily favorable or unfavorable.

The record also does not report the study's own sample-size justification, detailed statistical plan, or whether interim analyses were planned. Any planning illustration based on an observed effect is a hypothetical design aid, not evidence of the study's observed power or a substitute for the primary outcome result. Overall, the record establishes the question asked and some descriptive safety counts, but does not provide the primary pregnancy result needed to answer the stated effectiveness question.

13. Why This Trial Matters Statistically

This study raises a statistical question about evaluating an outcome after a specified sequence of procedures: participants relied on Essure micro-inserts for permanent birth control, and NovaSure endometrial ablation followed a successful Essure Confirmation Test. The primary endpoint was a pregnancy count at 1 year after NovaSure. This specificity makes the endpoint and its follow-up point clear in the registry description, while leaving important analysis details unresolved.

The registry record also illustrates why the design structure matters. It describes one group, does not state allocation, and explicitly says the study is not a randomized comparison and that the arms are not a like-for-like control comparison. Without a suitable comparison, an observed outcome in the described group cannot by itself show how outcomes would differ under another strategy. That distinction is central to interpreting effectiveness and safety claims.

Another statistical issue is the difference between enrollment and analysis. Enrollment was 211, but the number contributing to the 1-year endpoint is not reported in the registry record. For a follow-up outcome, information about completeness and missingness affects how a count or rate should be understood. The registry record also does not give the primary result or an interval describing its precision.

The safety entries further show why descriptive counts need context. The record lists serious and other adverse events, deaths, and selected serious event terms, but does not report attribution or detailed counting rules. Such information is needed to distinguish a recorded event from a conclusion that a device or procedure caused it. The study is statistically informative as an example of the limits imposed by missing results and limited design detail; its stated purpose alone does not resolve those limits.

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 primary limitation for interpreting effectiveness is that the pregnancy result at 1 year is not reported in the registry record. The record therefore does not provide the count, rate, or confidence interval for its primary endpoint. Without those values, neither the magnitude nor the precision of the primary finding can be described.

The enrollment of 211 does not establish how many participants had complete outcome information or were included in the primary analysis. The analysis population, completeness of follow-up, and handling of missing data are not reported in the registry record. The record also does not report the endpoint ascertainment procedures or further eligibility and participant characteristics.

The study is not described as a randomized comparison; allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. The described information therefore does not support a comparative causal interpretation. Details of any comparator, if applicable, are not reported in the registry record.

Safety interpretation is limited by the lack of reported event attribution, observation period, and event-counting definitions. The listed counts and percentages do not establish whether events were related to the device or procedure, and the registry record does not clarify whether the listed event terms could overlap within participants.

The record lists three outcome measures and two analyses, but the detailed statistical plan, multiplicity approach, and analysis methods are not reported in the registry record. The study's own sample-size justification and any interim analyses are also not reported. These limitations prevent a fuller assessment of how the outcomes were analyzed and how robust the findings would be to alternative assumptions.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study to Evaluate the Effectiveness of Essure Post-NovaSure Radiofrequency Endometrial Ablation Procedure Following a Successful Essure Confirmation Test — NCT01740687.
• Registry record last updated 2023-02-06; status last verified 2023-02.
• Results first posted 2023-02-06.
• 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.

18. Record Summary

The registry record describes a completed post-approval study sponsored by Bayer, with enrollment of 211. Its purpose was to evaluate the effectiveness and safety of the Essure System when NovaSure endometrial ablation followed a successful Essure Confirmation Test. The listed group relied on Essure micro-inserts for permanent birth control. The record lists Contraception and Menorrhagia as conditions.

The primary endpoint was the number of pregnancies at 1 year after NovaSure endometrial ablation. The pregnancy result is not reported in the registry record. A secondary outcome concerns adverse events when NovaSure was performed in the presence of Essure inserts. The safety entries list 18 affected by serious adverse events, 95 affected by other adverse events, and 1 death among the recorded group, with selected serious event terms and percentages.

The record does not state allocation and cautions that this is not a randomized comparison or a like-for-like control comparison. The analysis population, missing-data methods, detailed analysis plan, and sample-size justification are not reported in the registry record.