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 Amlodipine Versus Nifedipine ER for the Management of Postpartum Hypertension (NCT04790279), a randomized phase 4 study. The primary outcome is Length of Stay.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04790279 |
| Phase | Phase 4 |
| Condition | Hypertension in Pregnancy |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 175 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Prisma Health-Upstate |
| Results posted | Yes |
2. Clinical Question
Population
People treated for hypertension in the postpartum period. The registry describes hypertension in pregnancy as the condition and gives the primary endpoint timeframe as the hospital stay after delivery. Detailed eligibility criteria and the characteristics of enrolled participants are not reported in the registry record.
Intervention
Amlodipine, a drug in the same class as nifedipine ER according to the study summary. The registry describes the trial as testing whether amlodipine is noninferior for managing postpartum hypertension. Dosing and other treatment details are not reported in the registry record.
Comparator
Nifedipine ER, an established medication used in the postpartum setting according to the study summary. The record identifies both medications as trial interventions but does not report dosing, titration, or other details that would clarify how treatment was delivered or adjusted.
Primary question
The stated question is whether amlodipine is noninferior to nifedipine ER for postpartum hypertension management. The posted primary outcome is length of stay from delivery until discharge, measured in hours. The registry gives arm-specific medians and confidence intervals, but a noninferiority margin and a formal comparative noninferiority result are not reported in the registry record.
The clinical question is framed around a comparison between two medications, while the posted primary measure is time in hospital after delivery. Length of stay can describe the course of the hospital admission, but it is not itself a direct measure of blood pressure control. The record also lists secondary outcomes related to acute treatments, side effects, discontinuation, readmission, breastfeeding duration, and breastfeeding satisfaction. These outcomes broaden the questions considered, but the posted summaries do not replace a prespecified, formal assessment of the primary noninferiority question.
3. Trial Design
NCT04790279 is titled “Amlodipine Versus Nifedipine ER for the Management of Postpartum Hypertension.” The official title identifies it as a randomized controlled noninferiority trial. The registry lists the study as phase 4, randomized, open-label, and parallel-group. It reports enrollment of 175 and a completed status. The recorded start date is 2021-04-09, and the primary completion date is 2022-12-13. Prisma Health-Upstate is listed as the sponsor.
Participants were assigned to amlodipine or nifedipine ER. The record does not report the randomization sequence method, allocation concealment, treatment dose, treatment duration, or detailed arm procedures. Masking is listed as none, so the study was not blinded according to the registry classification. How that open-label design was handled in outcome assessment is not reported in the registry record.
The primary endpoint is length of stay from delivery until discharge, with a timeframe described as through the hospital stay, on average 2-5 days. The arm-level results list 87 participants for amlodipine and 88 for nifedipine ER. The record describes the primary population as “Amlodipine Intent To Treat,” but the precise population definition and the analysis population used for a between-arm comparison are not reported in the registry record.
The noninferiority framing makes details of the design and analysis especially important. A noninferiority assessment ordinarily depends on a prespecified margin and an analysis that compares treatment effects against that margin. The registry record does not report the margin, a sample-size justification, the planned statistical analysis, or a formal primary comparison. The enrollment figure alone therefore does not show whether the trial was designed or analyzed with adequate precision for its stated noninferiority objective.
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: Patients were randomized at the time of enrollment. Only patients meeting pre-defined criteria were started on an anti-hypertensive.
Overall Study
| Stage | Amlodipine | Nifedipine ER |
|---|---|---|
| STARTED | 87 | 88 |
| COMPLETED | 51 | 69 |
| NOT COMPLETED | 36 | 19 |
Reasons for not completing this period:
| Reason | Amlodipine | Nifedipine ER |
|---|---|---|
| Did not meet medication start criteria | 27 | 15 |
| Required long acting antihypertensive intrapartum | 1 | 0 |
| Protocol Violation | 8 | 3 |
| Developed complication requiring alternative regimen | 0 | 1 |
Analysis population for the primary outcome, as defined in the registry: Amlodipine Intent To Treat
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.
| Characteristic | Unit | Amlodipine | Nifedipine ER | Total |
|---|---|---|---|---|
| Participants analysed | 87 | 88 | 175 | |
| Age, Continuous | years | 27.9 (SD 6.8) | 27.8 (SD 5.9) | 27.8 (SD 6.3) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Race and Ethnicity Not Collected | Participants | — | — | 0 |
| Region of Enrollment: United States | Participants | 87 | 88 | 175 |
| BMI at delivery | kg/m2 | 36.8 (SD 9.3) | 37.0 (SD 10.1) | 36.9 (SD 9.7) |
| Parity | number of deliveries | 1 (0 to 9) | 1 (0 to 5) | 1 (0 to 9) |
| Gestational age at delivery | weeks | 35.7 (SD 2.5) | 35.6 (SD 3.3) | 35.6 (SD 2.9) |
| Mode of delivery: Vaginal | participants | 40 | 44 | 84 |
| Mode of delivery: Cesarean | participants | 47 | 44 | 91 |
| Hypertensive diagnosis: Chronic hypertension | participants | 21 | 22 | 43 |
| Hypertensive diagnosis: Preeclampsia without severe features | participants | 3 | 3 | 6 |
| Hypertensive diagnosis: Preeclampsia with severe features | participants | 84 | 81 | 165 |
| Diabetes: None | Participants | 71 | 66 | 137 |
| Diabetes: Gestational | Participants | 8 | 15 | 23 |
| Diabetes: Pre-gestational | Participants | 8 | 7 | 15 |
6. Primary Endpoint
The registry lists the primary outcome as Length of Stay, measured over Through hospital stay, on average 2-5 days.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | hours |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is length of stay, measured in hours from delivery until discharge. The registry describes the timeframe as through the hospital stay, on average 2-5 days. It reports the median length of stay for each treatment group, together with a 95% confidence interval. The posted median is 73.5 hours for amlodipine, with a confidence interval from 67.0 to 81.0 hours; for nifedipine ER, the median is 72.0 hours, with a confidence interval from 66.5 to 78.5 hours.
A median describes the center of a distribution by identifying the point at which half of observations are no greater and half are no smaller. It can be useful when a measure such as hospital stay is not well represented by an average or may have a skewed distribution. A confidence interval conveys uncertainty around an estimate; it is not a range that contains every participant’s stay.
Length of stay is a practical hospital-course measure, but it does not directly quantify blood pressure response or medication tolerability. Discharge timing may also reflect clinical and operational considerations beyond the treatment being compared. The registry presents arm-specific medians, not a primary between-group effect estimate or test. A comparative interpretation of the primary endpoint therefore cannot be established from the posted medians alone.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary results describe similar-looking arm-level medians for length of stay: 73.5 hours with amlodipine and 72.0 hours with nifedipine ER. The corresponding 95% confidence intervals are 67.0 to 81.0 hours and 66.5 to 78.5 hours. These are estimates for each group separately. The registry does not post a treatment contrast, confidence interval for that contrast, or primary p-value, so the precision of the between-group difference cannot be read directly from the primary results.
Similarity between two medians is not, by itself, evidence of noninferiority. A noninferiority conclusion requires a prespecified clinical margin and an analysis that shows the treatment effect is sufficiently precise relative to that margin. Neither the margin nor a formal noninferiority analysis is reported in the registry record. The posted data therefore describe length of stay in each arm, but do not establish whether the stated noninferiority criterion was met.
The registry’s secondary outcomes include participant counts for readmission, breastfeeding duration of 6+ weeks, and satisfaction with breastfeeding experience. The associated unadjusted estimates have confidence intervals that include no difference, and the registry lists no reported analyses for these outcomes. These results are exploratory descriptions rather than strong evidence for a treatment difference. The analyzed participant counts also vary across the secondary outcomes, and reasons for those differing counts are not reported in the registry record.
Safety entries report serious adverse events affecting 4 participants in each arm, with zero deaths reported in either group. Other adverse events are also listed. These counts should be read in the context of the stated at-risk groups and the registry’s event reporting, rather than as a complete comparative safety analysis. The record does not provide an adjusted comparison or detailed event-level timing and attribution.
Overall, the record offers arm-level information on the primary endpoint and selected secondary and safety outcomes. It does not report enough of the planned analysis to resolve the main inferential question. In particular, the absent noninferiority margin and comparative primary estimate limit conclusions about whether the two treatments met the trial’s stated objective. The posted results should be understood as descriptive evidence with important uncertainty, not as a definitive demonstration of equivalence or noninferiority.
9. Statistical Methods Explained
What do the primary summaries represent?
The registry reports a median and 95% confidence interval for length of stay in each arm. The median is a measure of central location that is less affected than the mean by unusually long stays. A confidence interval describes the statistical uncertainty around an estimate under the analysis method used. It does not show the range of individual participant values, and intervals for two separate arm estimates are not the same as a confidence interval for the difference between arms.
For a direct treatment comparison, an analysis would ordinarily estimate a contrast between groups and report its uncertainty. The primary endpoint entry does not include such a contrast or a p-value. A visual or numerical comparison of the two arm-specific intervals cannot substitute for a direct analysis. In general, overlap or non-overlap of separate confidence intervals is not a formal test of the difference between the underlying groups.
What does noninferiority require?
General explanation: a noninferiority study asks whether the result for one treatment is not unacceptably worse than the result for a comparator, according to a margin chosen before examining the results. The margin defines the largest difference that would still count as noninferior for the purpose of the study. The analysis needs to compare the estimated treatment effect and its uncertainty with that margin, using an appropriate direction and endpoint definition.
The registry names noninferiority in the official title and study summary, but the margin, its rationale, the statistical plan, and a formal primary noninferiority result are not reported in the registry record. The arm-level medians therefore cannot answer the noninferiority question by themselves. The record also does not state whether additional prespecified criteria were used to support that conclusion.
How should the secondary comparisons be read?
The posted secondary comparisons are binary outcomes expressed as risk differences, with confidence intervals and unadjusted p-values. A risk difference describes the difference between two event proportions, in the orientation used for the comparison. Its confidence interval communicates uncertainty in that estimated difference. When the interval includes zero, the data are compatible with no difference as well as with effects in either direction covered by the interval. An unadjusted p-value addresses a single comparison without accounting for the fact that several outcomes may have been examined.
These comparisons are not listed as reported analyses in the registry record. They should be treated as unadjusted statistical summaries, not as confirmed prespecified findings. Their uncertainty is particularly relevant where outcome-specific participant counts are limited. The record does not report adjusted estimates, an analysis plan for the secondary outcomes, or a multiplicity procedure.
What are the planning illustrations?
The planning illustrations are based on the observed effect and are not the trial’s own design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The illustrations consider detecting 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. Their sample-size values are participants per arm for 80% power and participants per arm for 90% power.
These are hypothetical planning quantities, not observed power and not evidence that the completed study had a particular probability of detecting an effect. Because the illustrations use effects estimated from the observed results, they depend on those estimates and their uncertainty. They do not establish that the trial was planned around the same assumptions, nor do they supply the missing noninferiority margin or design rationale. The sample-size justification for the actual trial is not reported in the registry record.
More generally, power calculations depend on the endpoint, assumed effect, variability or event rate, significance level, allocation, and analysis method. A planning illustration is only as informative as those assumptions. For a noninferiority design, the margin and the analysis appropriate to that margin are central; an illustration based on an observed binary risk difference does not itself validate the design of a trial whose primary endpoint is length of stay.
What analysis details remain unclear?
The registry identifies the primary population as “Amlodipine Intent To Treat,” but does not define that population or report a corresponding comparative analysis population. The method used to handle missing outcome data, protocol deviations, or withdrawals is not reported in the registry record. The record also does not report an interim analysis plan, covariate adjustment, a distributional model for the primary endpoint, or sensitivity analyses. These omissions limit assessment of how robust the posted estimates are and how closely the analyses followed the stated noninferiority objective.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists multiple secondary outcomes and posts unadjusted comparisons for some of them. It does not report a statistical analysis plan, a prespecified hierarchy among outcomes, or a method for controlling the effects of multiple testing. Without that information, the secondary p-values should not be treated as if they were the result of a single isolated test. Repeated comparisons can increase the chance of observing a nominally unusual result even when there is no underlying difference. The posted secondary confidence intervals and p-values are therefore most useful as exploratory summaries.
Missing-data procedures are not reported in the registry record. The participant counts differ across the posted secondary outcomes, but the reasons for those differences are not given. It is not possible to determine whether outcomes were unavailable, not collected for all participants, or excluded for another reason. The record does not describe imputation, complete-case analysis, or sensitivity analyses for missing values.
The primary population label includes “Amlodipine Intent To Treat,” but the record does not define the population or explain how assigned participants were handled in the analysis. A corresponding between-arm analysis population is not reported. The record does not state whether analyses followed assignment regardless of treatment received, or how treatment discontinuation and protocol deviations were addressed.
These gaps matter because noninferiority conclusions can be sensitive to analysis choices. The record does not report the noninferiority margin, the planned primary analysis, or any sensitivity analysis supporting the primary conclusion. It also does not report interim analyses or stopping criteria. These items should be considered unreported, rather than assumed to have been absent from the conduct of the trial.
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 |
|---|---|---|---|
| Amlodipine | 4 | 53 | 7.5% |
| Nifedipine ER | 4 | 69 | 5.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Amlodipine | 0 of 53 |
| Nifedipine ER | 0 of 69 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Amlodipine | 19 of 53 |
| Nifedipine ER | 26 of 69 |
Most frequent serious adverse event terms
| Event term | Organ system | Amlodipine | Nifedipine ER |
|---|---|---|---|
| Readmission | Pregnancy, puerperium and perinatal conditions | 3 of 53 | 3 of 69 |
| Prolonged hospitalization | Pregnancy, puerperium and perinatal conditions | 1 of 53 | 1 of 69 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Amlodipine | Nifedipine ER |
|---|---|---|---|
| Prolonged hospitalization | Pregnancy, puerperium and perinatal conditions | 14 of 53 | 11 of 69 |
| Triage/ER visit | Pregnancy, puerperium and perinatal conditions | 5 of 53 | 9 of 69 |
| Side effect requiring discontinuation | Pregnancy, puerperium and perinatal conditions | 0 of 53 | 7 of 69 |
Serious events with the highest arm-level rate: readmission (5.7%), prolonged hospitalization (1.9%).
The registry reports serious adverse events for groups with 53 participants at risk in the amlodipine arm and 69 in the nifedipine ER arm. Serious events affected 4 participants in each group. The record reports zero deaths in both arms. These are counts within the registry’s listed at-risk groups; they should not be interpreted as a complete account of every possible event or as proof that risks are equal.
For other adverse events, the record lists 19 affected participants among 53 at risk with amlodipine and 26 among 69 at risk with nifedipine ER. The registry separately lists readmission at 5.7% and prolonged hospitalization at 1.9% among the top serious event terms. Those term percentages are not identified by treatment arm in the posted information, so they should not be attributed to either arm.
The safety figures are descriptive. No adjusted treatment comparison, event timing, severity breakdown beyond the serious classification, or detailed attribution analysis is reported in the registry record. The at-risk counts also differ from the primary endpoint arm counts. These figures provide a limited account of reported events, not a comprehensive comparative safety conclusion.
12. What the Result Does, and Does Not, Mean
The posted results describe a randomized comparison of amlodipine and nifedipine ER, with arm-specific median lengths of stay and selected secondary and safety summaries. The medians are 73.5 hours for amlodipine and 72.0 hours for nifedipine ER. Their reported confidence intervals describe uncertainty around each group’s median, not a direct estimate of how much one treatment differs from the other.
The study’s stated purpose is to assess noninferiority, but the registry record does not report the noninferiority margin or a formal comparative primary analysis. For that reason, the available primary results do not demonstrate that amlodipine is noninferior to nifedipine ER, nor do they demonstrate that it is inferior. The record also does not establish equivalence: failure to show a clear difference is not the same as showing that treatments are sufficiently similar within a prespecified range.
The secondary estimates are also uncertain and unadjusted, and some listed outcomes have no posted numerical summary. They can describe what was recorded among the participants included for each measure, but they do not provide definitive evidence of benefit, harm, or equivalence. The safety entries report events and deaths as recorded, but the limited detail and lack of comparative analysis prevent a comprehensive safety judgment.
These findings should be interpreted as registry-posted results with incomplete information about the analysis plan and outcome availability. They do not establish how broadly the results apply beyond the enrolled participants, whose detailed characteristics are not reported in the registry record. The record supports a description of observed data, but not a firm conclusion on the trial’s noninferiority objective.
13. Why This Trial Matters Statistically
This trial illustrates why a study’s title and its posted results need to be read together. The official title describes a randomized noninferiority trial, but interpreting that design requires more than comparing the observed outcomes by eye. A prespecified margin, a treatment-effect estimate, and uncertainty around that estimate are central to judging whether the noninferiority question was answered. Those details are not reported in the registry record.
The primary endpoint also shows the distinction between arm-level summaries and comparative inference. Medians and confidence intervals describe each group’s length of stay, but they do not directly quantify the difference between groups. A treatment comparison needs its own estimate and uncertainty. Without that, the primary result is descriptive even though the trial was randomized.
The secondary outcomes raise further statistical issues. Outcome-specific participant counts vary, comparisons are unadjusted, and no multiplicity procedure is reported. These features do not make the results unusable, but they affect how much weight each estimate can carry. Wide uncertainty and multiple exploratory comparisons call for restraint rather than treating any single secondary result as conclusive.
Finally, planning calculations based on observed effects are not the same as a trial’s original sample-size justification or evidence of observed power. They can illustrate how sample-size requirements change under stated assumptions, but cannot reconstruct the actual design rationale. The record is a useful example of how transparent reporting of estimands, margins, analysis populations, missing-data handling, and multiplicity is necessary for readers to evaluate a noninferiority trial statistically.
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 affect interpretation. The registry does not report a noninferiority margin, the justification for that margin, or a formal primary comparison. Since the stated objective is noninferiority, these omissions prevent assessment of whether the primary result met the criterion the investigators intended to test.
The primary outcome is reported as separate arm medians and confidence intervals, without a between-arm estimate or p-value. The record does not give details of the method used to analyze length of stay or whether any factors were accounted for in that analysis. The primary population label is not fully defined, and the record does not explain how the participants assigned to each arm were handled in the comparative analysis.
There is limited information about outcome completeness. The primary arm counts are 87 and 88, whereas the secondary outcome counts differ across measures. Reasons for these differences and the handling of missing outcomes are not reported in the registry record. Participant characteristics, eligibility criteria, treatment doses, and detailed intervention procedures are also not reported, limiting assessment of who was studied and how closely the findings might apply elsewhere.
The study is listed as unmasked, and the record does not explain whether outcome assessment or other procedures reduced the potential influence of knowing treatment assignment. For the secondary comparisons, no reported analyses or multiplicity adjustment are listed. Safety information is summarized by counts and selected serious event terms, without a full comparative analysis. These limitations leave important questions about precision, analysis choices, and completeness unresolved.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Amlodipine Versus Nifedipine ER for the Management of Postpartum Hypertension — NCT04790279.
- Registry record last updated 2024-10-28; status last verified 2022-12.
- Results first posted 2024-10-28.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT04790279 is a completed, randomized, open-label, parallel-group phase 4 trial sponsored by Prisma Health-Upstate. It enrolled 175 participants and compared amlodipine with nifedipine ER for postpartum hypertension. The registry gives length of stay from delivery to discharge as the primary endpoint and reports arm-specific medians with 95% confidence intervals.
It also lists secondary outcomes related to acute treatment, side effects, medication discontinuation, readmission, breastfeeding duration, and breastfeeding satisfaction. Numerical summaries and unadjusted comparisons are posted for some secondary outcomes; the record lists no reported analyses for them. Safety entries include serious and other adverse events and deaths.
The registry record does not report a noninferiority margin, a formal comparative primary result, or key details of the statistical plan, missing-data handling, and analysis populations. The posted data therefore describe the observed results but do not resolve the stated noninferiority question.