This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for eSET Plus Single Embryo Cryotransfer vs Double Embryo Transfer (NCT01909570), a randomized na study. The primary outcome is Clinical Pregnancy Rate.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01909570 |
| Phase | NA |
| Condition | Infertility, Pregnancy, Multiple |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 194 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University Hospital Virgen de las Nieves |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes women aged under 38 years with BMI between 19-29 kg/m2 and FSH <15mUI/mL on the third day. Participants were to be in their first IVF/ICSI cycle, or a second cycle after a prior attempt with a positive pregnancy test result. The infertile period was to be less than five years. The description also mentions no previous uterine surgery and no uterine malformations, then ends without completing the eligibility details. The full eligibility criteria are not reported in the registry record.
Intervention
One strategy was elective single embryo transfer after FIV/ICSI, followed by cryotransfer of a single embryo, or a single embryo in case of no fresh conception. The record describes this as the elective single embryo transfer arm.
Comparator
The comparison strategy was transfer of two fresh embryos after FIV/ICSI. The record calls this double embryo transfer.
Primary question
The trial asked whether a policy of elective single embryo transfer plus single embryo cryotransfer was as effective as double embryo transfer in terms of clinical pregnancy rate. Clinical pregnancy was defined by a gestational sac with heartbeat on transvaginal ultrasonography at the 7th weeks of pregnancy. The primary outcome timeframe is seven weeks after embryo transfer. The registry record does not report a formal equivalence or non-inferiority margin, so the question alone does not establish that either design was used.
3. Trial Design
The registry describes NCT01909570 as a randomized, parallel-group clinical trial. It compares two embryo-transfer strategies: elective single embryo transfer with a single embryo cryotransfer as described in the arm record, and double embryo transfer using two fresh embryos. The masking status is listed as none. The record therefore identifies a randomized comparison without masking; it does not give further detail about sequence generation, allocation concealment, who knew assignments, or how treatment assignment was implemented. Those details are not reported in the registry record.
The registry lists enrollment as 194. For the primary outcome, the arm-level records give denominators of 84 for elective single embryo transfer and 91 for double embryo transfer. The record does not explain the difference between the enrollment figure and these outcome denominators. It also does not describe participant flow, withdrawals, exclusions from analysis, or whether the endpoint denominators reflect all randomized participants. It would therefore be inappropriate to infer an analysis population or reconcile the counts from the information recorded.
The study status is completed. The listed start is 2010-01 and the primary completion is 2013-12. The sponsor is University Hospital Virgen de las Nieves. The phase is listed as NA. These registry entries identify the study and broad design, but do not supply a protocol-level account of conduct. In particular, planned sample-size justification, randomization procedures, analysis populations, interim monitoring, and the statistical analysis plan are not reported in the registry record.
The stated purpose was to determine whether the combined single-transfer policy was as effective as double embryo transfer with respect to clinical pregnancy rate. The presence of a randomized design does not by itself show how the investigators intended to interpret that question statistically. A pre-specified margin and an appropriate analysis would be needed to assess equivalence or non-inferiority; neither is reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: A total of 194 women aged under 38 years were included in the study. Of these, 19 women were not randomised. The reasons were refusion to participate (n= 6), economic reasons (n = 2), participating in another study (n= 7) and not meeting criteria in further evaluation (n = 4).
Overall Study
| Stage | Elective Single Embryo Transfer | Double Embryo Transfer |
|---|---|---|
| STARTED | 84 | 91 |
| COMPLETED | 57 | 64 |
| NOT COMPLETED | 27 | 27 |
Analysis population for the primary outcome, as defined in the registry: Women aged under 38 years, with BMI between 19-29 kg/m2, FSH \<15mUI/mL on the third day and first cycle of IVF/ICSI or second cycle after a prior attempt with a positive pregnancy test result. The infertile period must be less of five years, without previous uterine surgery, uterine malformations, neither repeated spontaneous abortions.
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.
Population: Women aged under 38 years, with BMI between 19-29 kg/m2, FSH \<15mUI/mL on the third day and first cycle of IVF/ICSI or second cycle after a prior attempt with a positive pregnancy test result. The infertile period must be less of five years, without previous uterine surgery, uterine malformations, neither repeated spontaneous abortions.
| Characteristic | Unit | Elective Single Embryo Transfer | Double Embryo Transfer | Total |
|---|---|---|---|---|
| Participants analysed | 84 | 91 | 175 | |
| Age, Continuous | years | 32.2 (SD 3.6) | 31.7 (SD 3.8) | 32.0 (SD 3.7) |
| Sex: Female, Male: Female | Participants | 84 | 91 | 175 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): White | Participants | 84 | 91 | 175 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: Spain | participants | 84 | 91 | 175 |
6. Primary Endpoint
The registry lists the primary outcome as Clinical Pregnancy Rate, measured over Seven weeks after embryo transfer.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of pregnancy per transfer |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is clinical pregnancy rate, recorded as a percentage of pregnancy per transfer. A clinical pregnancy was defined as the presence of a gestational sac with heartbeat on transvaginal ultrasonography at the 7th weeks of pregnancy. The stated timeframe is seven weeks after embryo transfer.
This endpoint captures a pregnancy meeting the registry's ultrasound definition rather than pregnancy based only on an earlier test result. A rate expresses the occurrence of the endpoint in relation to transfers, which makes the unit relevant to the trial's comparison of transfer strategies. The record does not further explain how repeated transfers, cryotransfers, or participants with more than one transfer were handled in the denominator. The arm denominators are recorded as 84 and 91, but the denominator rules are not described beyond the endpoint's stated unit.
Clinical pregnancy is not the only outcome of interest in the record. Multiple Pregnancy Rate is listed as a secondary outcome. However, no result for that secondary outcome is included in the registry record recorded for the posted results. Thus, the primary endpoint gives information about the registry-defined clinical pregnancy outcome, but it does not by itself describe multiple pregnancy or other outcomes that may matter when comparing transfer strategies.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary outcome values are 44.0% for elective single embryo transfer and 37.4% for double embryo transfer. These are reported as clinical pregnancy percentages per transfer. The corresponding outcome denominators are 84 and 91. The numerical percentage is higher in the elective single embryo transfer arm in the registry record, but these descriptive values alone do not establish whether the difference is compatible with chance, how precise the comparison is, or whether a clinically meaningful criterion was met.
No confidence interval, p-value, adjusted effect estimate, or statistical test result is reported in the registry record. Without an uncertainty estimate or inferential analysis, the observed percentages should not be read as proof of superiority, equivalence, or non-inferiority. The stated trial purpose uses the phrase “as effective,” but the record does not identify a non-inferiority or equivalence margin or give an analysis plan that would show how that claim was to be tested. A higher point estimate in one arm cannot answer those questions on its own.
The record lists the clinical pregnancy rate as a percentage per transfer. It does not explain whether denominators represent all randomized participants, all participants who received an embryo transfer, or another analysis population. It also does not report participant flow or missing outcome handling. The enrollment figure is 194, while the primary outcome arm records list denominators of 84 and 91; the registry does not explain how those figures relate. Consequently, the outcome values should be understood in the context of the posted denominators, without treating them as an analysis of every enrolled participant unless that is established elsewhere.
These results are specific to the registry's endpoint definition and population description. The population entry describes women meeting several eligibility conditions, but its text is incomplete. The record does not provide enough information to assess the extent to which the randomized population matched all intended eligibility criteria or how broadly results may apply beyond the trial. The randomized parallel design is relevant to interpreting a comparison, but its strengths cannot substitute for absent details about conduct, analysis, and uncertainty.
The secondary outcome listing includes Multiple Pregnancy Rate, an outcome that could add context to the comparison of embryo-transfer policies. No arm-level result for that endpoint is reported in the registry record. Therefore, the posted primary values do not provide a complete account of all outcome dimensions identified in the record.
9. Statistical Methods Explained
The registry record contains descriptive primary outcome values but no statistical analysis results. The distinction between a descriptive result and an inferential comparison is important: arm percentages show what was recorded in each group, while an inferential analysis would quantify the uncertainty in the contrast or evaluate it against a prespecified criterion. The posted record gives neither a confidence interval nor a p-value for the primary comparison.
What does a confidence interval add?
In general, a confidence interval describes uncertainty around an estimated quantity under the assumptions of the statistical method used. For a treatment comparison, an interval around an effect estimate can show which effect sizes are reasonably compatible with the observed data and analysis model. Its width reflects precision: a narrower interval indicates greater precision under that model, while a wider interval indicates greater uncertainty. No interval for this comparison is reported in the registry record, so the precision of the difference between the posted percentages cannot be assessed from the registry results alone.
What can be concluded from the arm percentages?
The percentages, 44.0% and 37.4%, are observed summaries for the two listed arms. They can be described as arm-level outcome values, but they do not, without an analysis, establish that the underlying outcome rates differ. Randomization is intended to support a fair comparison by assigning participants to strategies, but a registry entry that reports randomization does not show the details of allocation or the analysis actually performed. The posted record also does not describe adjustment for prognostic factors, handling of repeated observations, or the denominator rules beyond the per-transfer endpoint unit.
How should a planning illustration be read?
General sample-size planning asks how many participants per arm would be needed to detect an effect of a specified size under selected assumptions. The planning illustrations associated with this record are described as based on the observed effect, not on the trial's own design. They assume a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is stated as a fraction of the observed effect. Such values are planning illustrations, not evidence about the trial's observed power and not a replacement for a documented sample-size justification. The registry does not report the trial's own sample-size assumptions or justification.
Planning based on an observed effect should be interpreted cautiously in general. The observed effect is itself uncertain, and using it as the anchor for future planning does not remove that uncertainty. Considering smaller fractions of an observed effect can illustrate how planning requirements change when aiming to detect a less pronounced effect, but those illustrations do not establish that any particular effect is clinically important. No clinical threshold for a meaningful difference is reported in the registry record.
Why does the outcome type matter?
The primary outcome is recorded as a percentage, and the registry entries classify its analysis kind as count/other rather than a continuous mean. A percentage arises from outcome counts relative to a denominator. General methods for such data often model the probability of an event or compare proportions, with uncertainty depending on the event counts, denominator sizes, and modeling assumptions. A record that reports only percentages and denominators does not reveal which statistical method was used. The registry does not list an analysis for this endpoint, so no particular model should be attributed to the investigators.
Some count outcomes can show over-dispersion: variability greater than a simple model assumes. In general, ignoring over-dispersion can make uncertainty estimates too small and statistical evidence appear stronger than warranted. This is a general consideration for count data, not a claim about this trial's primary endpoint or analysis. The registry provides no model specification, variance assessment, or residual checks, so it is not possible to determine whether over-dispersion was relevant to any analysis.
Was the stated objective tested as equivalence or non-inferiority?
General equivalence testing asks whether the treatment difference lies within a prespecified range considered acceptably small in either direction. General non-inferiority testing asks whether one approach is not worse than another by more than a prespecified margin. Both require a defensible margin and an analysis aligned with that objective. The registry's wording that the strategies were compared in terms of whether one was “as effective” does not, by itself, identify either framework. No margin, hypothesis, confidence-bound criterion, or formal test is reported in the registry record. It is therefore not possible to conclude that an equivalence or non-inferiority claim was established.
Overall, the available result supports a descriptive reading of the two posted clinical pregnancy percentages. It does not support a quantified estimate of comparative uncertainty or a formal decision about the trial's stated effectiveness question. Additional protocol and analysis information would be needed to interpret the statistical evidence beyond those descriptive values.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists Multiple Pregnancy Rate as a secondary outcome and reports three outcome measures overall. It does not give a result for the named secondary outcome in the registry record recorded. The registry record also lists no statistical analyses. Thus there is no reported set of primary and secondary hypothesis tests from which to assess how multiplicity was handled.
In general, testing several outcomes or conducting multiple comparisons can increase the chance of finding an apparently notable result by chance. Statistical plans may address this through a prespecified hierarchy, adjusted significance thresholds, or other approaches. None of those procedures is reported in the registry record, so no multiplicity adjustment should be assumed. The absence of a secondary result also means the clinical pregnancy percentages cannot be supplemented with a posted comparison of multiple pregnancy.
Missing-data methods are not reported in the registry record. There is no description of how unavailable outcome measurements, withdrawals, or participants without a transfer were handled. Nor does the record identify an intention-to-treat, per-protocol, or other named analysis population. These omissions matter because analysis populations and missing outcomes can affect the interpretation of a randomized comparison.
The record lists enrollment as 194 and primary outcome denominators of 84 and 91 across the arms. It does not explain participant disposition or how the outcome denominators were obtained. Those figures should not be treated as proof of a particular exclusion process or analysis set. The registry information does not establish whether the primary outcome was observed for every randomized participant, nor does it report a sensitivity analysis for missing outcomes.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Elective Single Embryo Transfer | 0 | 84 | 0.0% |
| Double Embryo Transfer | 0 | 91 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Elective Single Embryo Transfer | 3 of 84 |
| Double Embryo Transfer | 5 of 91 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Elective Single Embryo Transfer | Double Embryo Transfer |
|---|---|---|---|
| premature birth | Pregnancy, puerperium and perinatal conditions | 3 of 84 | 3 of 91 |
| Hiperstimulation Ovarian Syndrome | Reproductive system and breast disorders | 0 of 84 | 2 of 91 |
The registry lists zero participants with a serious adverse event in the elective single embryo transfer group, with 84 at risk, and zero in the double embryo transfer group, with 91 at risk. These are the posted serious-event counts for the groups. They describe what was recorded in the registry and should not be interpreted as evidence that serious events are impossible or that no such events occurred outside the record's reporting period or definitions.
The record also lists other adverse events affecting 3 participants in the elective single embryo transfer group and 5 in the double embryo transfer group. The registry does not define the distinction between its serious and other adverse-event categories in the registry record, and it does not give event terms for the serious-event category. Death counts are not reported in the registry record.
Adverse-event counts are descriptive. Their interpretation depends on the event definitions, time period, ascertainment procedures, and completeness of reporting. Those details are not reported in the registry record. The counts do not, on their own, establish whether the groups differ in safety or whether an event was caused by an assigned strategy.
12. What the Result Does, and Does Not, Mean
The central reported finding is descriptive: the registry records clinical pregnancy percentages per transfer of 44.0% for elective single embryo transfer and 37.4% for double embryo transfer. The endpoint is defined by ultrasound evidence of a gestational sac with heartbeat at the 7th weeks of pregnancy, with a timeframe of seven weeks after embryo transfer. These are the observed arm-level values recorded for the primary outcome, not a complete inferential comparison.
The values do not show how precisely the underlying rates or their contrast are estimated. No confidence interval, p-value, or adjusted effect estimate is reported in the registry record. There is no basis in the posted results for claiming statistical significance, equivalence, non-inferiority, or superiority. The stated aim asks whether one strategy is as effective as the other, but the record gives no margin or analysis details needed to evaluate that type of claim.
The trial's randomized parallel design is relevant to the intended comparison, and the listed masking status is none. However, the registry does not report allocation procedures, participant flow, endpoint missingness, the analysis population, or the statistical methods used. The total enrollment and outcome denominators are recorded separately, without an explanation of their relationship. These limitations constrain what can be inferred from the reported outcome values.
The record identifies Multiple Pregnancy Rate as a secondary outcome but does not report its result. It also provides adverse-event counts, including zero serious adverse events recorded in each arm, but the details needed to assess event definitions and ascertainment are absent. The primary outcome should therefore not be treated as a complete evaluation of every potential benefit or harm associated with the strategies.
The appropriate reading is narrow: the registry records the two clinical pregnancy percentages and their arm denominators, but does not provide the inferential evidence or contextual details needed to determine the strength, precision, or broader implications of the comparison.
13. Why This Trial Matters Statistically
This trial illustrates why a registry result requires more than a pair of percentages to support a comparative conclusion. The primary outcome values give a direct descriptive view of clinical pregnancy per transfer in each randomized arm. Without an estimate of uncertainty, however, a reader cannot determine how much the observed contrast may reflect sampling variability or how compatible the data are with a range of possible underlying effects.
The stated objective also highlights the difference between asking whether two strategies are “as effective” and demonstrating equivalence or non-inferiority under a formal statistical framework. In general, those claims require a prespecified margin and an analysis designed to evaluate it. Neither is reported in the registry record. This distinction matters because a result that fails to show a conventional difference is not, by itself, evidence that strategies are equivalent.
The record further demonstrates the importance of knowing who contributed to an endpoint analysis. It lists overall enrollment and arm-specific outcome denominators, but does not explain their relationship or provide participant flow. Without that information, readers cannot establish whether the reported percentages reflect all randomized participants or a selected group with observed transfers and outcomes.
Finally, the listed secondary outcome and adverse-event counts show why outcome interpretation should consider more than the primary endpoint. The secondary multiple-pregnancy result is not reported, and the safety descriptions are limited. As a statistical example, the trial is useful for separating observed summaries from a complete, uncertainty-aware analysis and for recognizing the information needed to assess a randomized comparison.
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.
Several trial-specific limitations follow from the registry information. The eligibility description ends after mentioning no previous uterine surgery and uterine malformations, so the full population criteria are not reported in the registry record. This makes it difficult to establish the precise scope of the intended population from the entry alone. The strategy descriptions also provide only brief accounts of fresh transfer and cryotransfer; further procedural details are not reported.
Although allocation is listed as randomized, the record does not describe sequence generation or allocation concealment. Masking is listed as none, but it does not clarify which people involved in care, outcome assessment, or analysis knew the assigned strategy. These details are relevant to judging potential sources of bias, and they cannot be inferred from the broad design labels.
The primary outcome percentages are posted without confidence intervals, p-values, or a statistical model. The record does not state the planned analysis population, missing-data approach, or participant flow. It reports enrollment as 194 and outcome denominators of 84 and 91, without explaining the difference. These omissions limit assessment of how complete and representative the endpoint data were.
The registry describes a question about whether one strategy is as effective as the other, but reports no equivalence or non-inferiority margin. It also gives no sample-size justification for the trial, interim-analysis plan, or multiplicity strategy. The secondary multiple-pregnancy outcome is named but has no result in the record, while adverse-event definitions and ascertainment details are not reported. These limitations mean the posted record supports description of selected outcomes, but not a full assessment of the trial's statistical plan or all relevant results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: eSET Plus Single Embryo Cryotransfer vs Double Embryo Transfer — NCT01909570.
- Registry record last updated 2024-05-16; status last verified 2024-05.
- Results first posted 2015-02-20.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT01909570 is a completed randomized, parallel-group trial comparing elective single embryo transfer with a single embryo cryotransfer strategy against double embryo transfer. The registry lists no masking. Its primary outcome is clinical pregnancy rate per transfer, defined by a gestational sac with heartbeat on transvaginal ultrasonography at the 7th weeks of pregnancy, with a timeframe of seven weeks after embryo transfer.
The posted primary values are 44.0% for the elective single embryo transfer arm and 37.4% for the double embryo transfer arm. Their recorded outcome denominators are 84 and 91. No statistical analysis result or uncertainty estimate is reported in the registry record. Multiple Pregnancy Rate is listed as a secondary outcome, without a reported result in the registry record. The registry lists zero serious adverse events in both arms and other adverse events affecting 3 and 5 participants, respectively. Details on analysis populations, missing data, and participant flow are not reported.