A Mobile Health Intervention to Achieve Appropriate Gestational Weight Gain in Overweight/Obese Women: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Mobile Health Intervention to Achieve Appropriate Gestational Weight Gain in Overweight/Obese Women (NCT03880461), a randomized na study. The primary outcome is Total Gestational Weight Gain (GWG).

2. Clinical Question

The registry record describes a randomized, parallel-group trial with cluster randomization and double masking. Its central question concerns the mean amount of weight gained during pregnancy, not only whether each participant fell within a recommended range. The primary outcome was calculated from measured weight at 10 gestational weeks and the last measured pregnancy weight at delivery.

The intervention was designed as an adaptive approach: it began with lower-resource support, with more personalized messages and telephone coaching reserved for participants whose gestational weight gain was not within the recommended guidelines. The comparator was usual medical care. The record also lists outcomes concerning weight-gain patterns, physical activity, diet quality, postpartum weight retention, and infant growth.

The posted primary analysis reports a two-sided p-value but does not report the group means, an estimated difference, or a confidence interval. Accordingly, the registry record establishes that a statistical comparison was reported, but it does not show the size or direction of the difference in total gestational weight gain.

3. Trial Design

This was a randomized, double-masked, parallel-group cluster trial sponsored by Kaiser Permanente. Enrollment was 1335. The registry lists the phase as NA and the study status as completed. The recorded start date is 2021-01-21, and the primary completion date is 2024-03-28.

The intervention arm received a lifestyle intervention intended to help participants achieve gestational weight gain within the range recommended for their pre-pregnancy BMI. The described support included a telephone counseling session with a study dietician trained in motivational interviewing, technology-based tools, automated text messages, and weekly emails of core lifestyle sessions. A mobile health tool was described as transmitting data to a mobile website. Personalized text messages and one-to-one telephone coaching were intended for participants not meeting the weight-gain guidelines. Usual medical care was the control condition.

Although the record identifies the design as cluster randomized, it does not report the unit of randomization or describe how clusters were formed. It also does not identify who was masked or explain how masking was maintained. Those details matter when interpreting how allocation and outcome assessment were handled, but they are not reported in the registry record.

The primary outcome was total gestational weight gain, measured from 10 gestational weeks until delivery. The record lists secondary outcomes involving trimester-specific weekly weight-gain rate, weight-gain trajectory, physical activity, diet quality, postpartum weight retention, infant birthweight category, and infant growth. Maternal outcomes were to be assessed shortly before delivery and at 6 weeks postpartum; infant birthweight and weight at one year were also described. The registry record does not provide further details about recruitment, cluster counts, follow-up completeness, or the analytic handling of the clusters.

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:

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 Total Gestational Weight Gain (GWG), measured over From 10 gestational weeks until time of delivery (duration of up to 9 months).

The primary endpoint was total gestational weight gain in kilograms. It was defined as the last measured pregnancy weight at the time of delivery minus measured weight at 10 gestational weeks. The stated timeframe ran from 10 gestational weeks until delivery, described as a duration of up to 9 months. The outcome was summarized as a mean with standard deviation.

This measure captures the amount of weight gained over the specified pregnancy interval. It is useful for comparing average weight gain between groups, while the trial’s stated intervention goal was to help women remain within a recommended gestational weight-gain range for pre-pregnancy BMI. Those are related but distinct questions: a difference in mean weight gain would not, on its own, describe how many participants met the recommended range.

The registry record does not report the group means, standard deviations, estimated between-group difference, or confidence interval for this endpoint. It therefore does not allow readers to judge the size or precision of the observed difference from the posted primary result alone. It also does not describe how weights were handled when a measurement was unavailable or how timing differences around delivery were treated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: total gestational weight gain is expressed in kilograms and summarized as a mean. The reported comparison is a two-sided t-test. General statistical explanation: a t-test compares group means while accounting for variability in the observed values. A two-sided test considers departures in either direction rather than testing only whether one group’s mean is larger.

What does the p-value tell us?

The reported p-value is 0.014. In general, a p-value describes how compatible the observed data are with a specified null hypothesis under the assumptions of the test. It is not the probability that the null hypothesis is true, nor does it quantify the size of a difference. The registry labels the analysis as superiority, but the p-value alone does not reveal whether mean weight gain was higher or lower in the intervention arm.

To describe the result fully, readers would need the estimated difference between group means and a confidence interval. General statistical explanation: a confidence interval gives a range of values compatible with the data and the analysis model, and helps show the precision of an estimate. Neither the mean difference nor a confidence interval is reported in the registry result. The posted tables and plots should be consulted for their displayed content, but no unreported estimate can be inferred from the p-value.

Why does cluster randomization matter?

The registry identifies the study as cluster randomized and states that a simple individual-level re-analysis would be misleading. General statistical explanation: when assignment occurs by cluster, outcomes from people in the same cluster may be correlated. If that correlation is ignored, the analysis may treat the data as containing more independent information than they do, which can affect standard errors, confidence intervals, and p-values. Analyses of cluster-randomized trials generally need to account for clustering in a way suited to the design and data.

The registry record does not state the cluster unit, number of clusters, or the model or variance method used in the sponsor’s analysis. The reported test is described as a two-sided t-test, but that label alone does not show how clustering was addressed. Because the record flags the risk of an individual-level re-analysis, the sponsor’s reported analysis is the appropriate result to foreground; a new calculation from individual-level summary information would not be a reliable substitute.

What is the role of the mean and standard deviation?

General statistical explanation: a mean summarizes the average outcome in a group, while a standard deviation describes the spread of individual observations around that group’s mean. A comparison of means addresses average differences, not every participant’s experience. The primary outcome is defined as a mean with standard deviation, but the group-specific values are not reported in the registry result. Therefore, readers cannot assess the amount of variation or reconstruct the comparison from the displayed p-value alone.

How should planning calculations be read?

The page includes sample-size planning illustrations based on fractions of the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. These are planning illustrations, not observed power and not a description of the trial’s own design justification. The registry record does not report the trial’s sample-size justification. Because the trial is cluster randomized, any planning interpretation also needs to be distinguished from a simple individual-level calculation; the record’s warning is that an individual-level re-analysis would be misleading.

What remains uncertain from the methods record?

The record does not report the cluster-adjustment details, missing-data procedures, analysis population, or multiplicity handling. It does not state whether the primary analysis followed an intention-to-treat principle, how participants with incomplete weights were treated, or whether there were interim analyses. Those methods cannot be inferred from the fact that the trial was randomized, double masked, or completed. General statistical principle: these choices influence how an estimate and its uncertainty should be interpreted, so their absence limits independent appraisal of the reported result.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Intervention Arm - PATIENTS", "Usual Care Arm - PATIENTS")
n   <- c(591, 520)
m   <- c(10.5, 11.3)
sp  <- c(5.7, 5.9)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Intervention Arm - PATIENTS  591  10.500  5.700  10.040  10.960
CARM  Usual Care Arm - PATIENTS  520  11.300  5.900  10.792  11.808

11. Analyses Reported by the Sponsor

The sponsor’s own analysis is the only primary comparison shown. It is reported as a two-sided t-test for superiority, with p = 0.014. The registry record identifies the study as cluster randomized and specifically cautions that a simple individual-level re-analysis would be misleading. For that reason, this page does not replace the sponsor’s analysis with a recalculation from participant-level assumptions.

The registry result does not give the group means, mean difference, or confidence interval. There is therefore no posted effect estimate to compare with a recalculated estimate, and the sponsor’s result cannot be checked against a numerical re-calculation from the information in the record. The p-value describes the test result, not the magnitude or direction of the difference.

In general, a recalculation from summary statistics is an unadjusted check and may not reproduce a design-aware analysis. That distinction is particularly important for cluster-randomized studies, where the analysis must account for the grouping structure. No discrepancy between a sponsor analysis and a recalculation is reported; rather, the registry record states that only the sponsor’s analysis is shown because a simple individual-level re-analysis would be misleading.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and multiple secondary outcomes, including weight-gain rate and trajectory, physical activity, diet quality, postpartum weight retention, infant birthweight category, and infant growth. It also reports three analyses and ten outcome measures. These entries indicate that the posted primary comparison sits within a broader outcome set, but the registry record does not describe how the analyses were prioritized beyond identifying the primary outcome.

No multiplicity adjustment or testing hierarchy is reported in the registry record. General statistical explanation: when several outcomes or comparisons are tested, the chance of obtaining at least one small p-value by chance can increase. A prespecified adjustment or hierarchy can help readers understand how to interpret a set of tests. Without a reported plan, it is not possible to determine how the primary p-value was treated relative to other analyses or whether any adjustment was used.

The analysis population is not reported in the registry record. The record does not state whether the primary analysis included all randomized participants, only participants with measured outcome data, or another defined group. It also does not describe whether participants were analyzed according to their assigned group.

Missing-data procedures are not reported in the registry record. The primary outcome depends on measured weight at 10 gestational weeks and a later pregnancy weight at delivery, but the record does not say how missing or incomplete measurements were handled. It also does not describe imputation, sensitivity analyses, or follow-up completeness for the primary outcome. These omissions matter because the observed comparison may depend on which participants contributed measurements and how absent values were handled. The available record is not sufficient to determine whether missingness or multiplicity changed the interpretation of the reported test.

13. Safety Results

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

Deaths

Other (non-serious) adverse events

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

Most frequent non-serious adverse event terms

The registry reports no serious adverse events among 714 participants at risk in the intervention arm and no serious adverse events among 621 participants at risk in the usual-care arm. It reports zero deaths in each arm. For other adverse events, the registry reports 44 affected among 714 at risk in the intervention arm and 29 affected among 621 at risk in the usual-care arm.

These are descriptive counts as recorded, not a comparison adjusted for the cluster-randomized design. The record does not provide event-specific descriptions for the other adverse events, and no top serious-event terms are listed. It also does not state how adverse events were defined, collected, or attributed, or provide a statistical comparison of the groups for safety outcomes.

General statistical explanation: counts alone do not establish whether an apparent difference between groups is meaningful, particularly without information about event definitions, follow-up, and the analysis method. The absence of reported serious events in these registry entries does not establish that no such events occurred outside the recorded period or that the intervention is free of risk. These figures should be read as the posted safety record, not as a standalone conclusion about safety.

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

The posted result shows that the sponsor reported a statistically detectable difference in mean total gestational weight gain between the trial groups using a two-sided t-test, with p = 0.014. The trial compared a lifestyle intervention with usual medical care and focused on weight gain from 10 gestational weeks until delivery.

The record does not report the group means, estimated difference, or confidence interval. Therefore, the direction, magnitude, and precision of the difference are not available from the primary result as reported. A p-value cannot fill in those missing details. It also cannot show how many participants achieved the recommended weight-gain range, which is the intervention’s stated goal but is not the same as the mean outcome.

The primary result does not by itself establish how the intervention affected physical activity, diet quality, postpartum weight retention, or infant outcomes. Those outcomes are listed separately in the record; their results are not described in the primary analysis. Nor does the result establish that the observed finding applies beyond the participants and settings represented in this trial.

The cluster-randomized design is important to the interpretation. The registry explicitly cautions that a simple individual-level re-analysis would be misleading and presents only the sponsor’s analysis. Details of the sponsor’s cluster-adjustment method are not reported in the registry record, limiting independent assessment of the analysis.

In practical terms, the result is evidence of a reported between-group statistical difference, but it is not enough to describe the difference’s size or clinical relevance. A full interpretation would require the group summaries and estimated contrast with uncertainty, along with information on missing data, analysis populations, multiplicity, and the handling of clusters. This reading neither endorses nor rejects the intervention; it identifies what the posted statistical result can and cannot establish.

15. Why This Trial Matters Statistically

This trial is statistically notable because it combines a cluster-randomized design with a continuous primary outcome. That combination makes the choice of analysis important: the grouping created by cluster allocation can affect how uncertainty is estimated. The registry itself warns that simple individual-level re-analysis would be misleading, an important signal for readers who might otherwise try to reconstruct the result from summary values.

The primary endpoint also illustrates the distinction between an average and a target range. The intervention aimed to support gestational weight gain within recommendations for pre-pregnancy BMI, while the primary analysis compared mean total gain. A mean comparison can address average differences between arms, but it does not directly report how many participants were within the recommended range or how outcomes varied across participants.

The posted p-value, 0.014, is not accompanied by the estimated difference or confidence interval. This makes the trial a useful example of why statistical significance alone is incomplete: readers need the direction and scale of an effect, together with its precision, to understand the result. The registry’s missing analysis details also show why transparent reporting of clustering, missing data, analysis populations, and multiplicity is important for evaluating a clinical trial.

The record presents a broad set of maternal and infant outcomes, while the primary result addresses only total gestational weight gain. Keeping the primary endpoint distinct from secondary outcomes helps prevent a single test from being mistaken for a complete account of a multicomponent intervention or its effects across pregnancy and postpartum follow-up.

16. 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 result is incomplete as a description of the treatment contrast. The registry reports p = 0.014 but not the group means, mean difference, or confidence interval. Consequently, readers cannot determine the direction, size, or precision of the difference in total gestational weight gain from that result alone.

Important design and analysis details are absent. The record identifies cluster randomization but does not state the randomization unit, number of clusters, or the method used to account for clustering in the sponsor’s analysis. It identifies double masking but does not say who was masked. It also does not report the analysis population, missing-data procedures, multiplicity handling, or whether interim analyses were conducted.

The primary outcome depends on weights measured at 10 gestational weeks and at delivery. The registry does not describe how unavailable weights, measurements outside the intended timing, or incomplete follow-up were handled. The posted information also does not provide enough detail to assess whether the primary analysis included all randomized participants.

The safety record gives counts but does not describe the other adverse events or explain event collection and attribution. The record does not report a comparative safety analysis. These limitations do not negate the posted result; they define what can be assessed from the registry record and what remains uncertain.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: A Mobile Health Intervention to Achieve Appropriate Gestational Weight Gain in Overweight/Obese Women — NCT03880461.
• Registry record last updated 2026-07-29; status last verified 2025-03.
• Results first posted 2025-04-18.
• 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.

20. Record Summary

The completed study, NCT03880461, was a randomized, double-masked, parallel-group cluster trial sponsored by Kaiser Permanente. It enrolled 1335 participants and compared a lifestyle intervention with usual medical care. The intervention combined counseling and technology-based support, with additional personalized messages and telephone coaching intended for participants not meeting gestational weight-gain guidelines.

The primary endpoint was mean total gestational weight gain in kilograms, calculated from measured weight at 10 gestational weeks to the last measured pregnancy weight at delivery. The sponsor reported a two-sided t-test for superiority with p = 0.014. Group means, an estimated difference, and a confidence interval are not reported in the primary result. The registry cautions that simple individual-level re-analysis would be misleading because the study was cluster randomized, so only the sponsor’s analysis is shown.

The record lists maternal and infant secondary outcomes and reports adverse-event counts. It does not report key details about clustering methods, missing data, analysis populations, or multiplicity.