Controlled Trial of Prenatal Vitamin D3 Supplementation to Prevent Vitamin D Deficiency in Mothers and Their Infants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Controlled Trial of Prenatal Vitamin D3 Supplementation to Prevent Vitamin D Deficiency in Mothers and Their Infants (NCT00610688), a randomized phase 3 study. The primary outcome is Maternal Serum and Neonatal Serum 25-hydroxyvitamin D Measurement.

2. Clinical Question

The study’s stated purpose was to compare a higher dose with a commonly recommended dose for achieving or maintaining sufficient vitamin D blood levels during pregnancy and in newborn infants, and to assess infant growth. That purpose describes the research question, not a demonstrated result. Numerical outcome values and between-group comparisons are not reported in the registry record, so the direction and size of any differences cannot be assessed from the registry information.

3. Trial Design

The registry describes a phase 3, randomized, double-masked, parallel-group trial. It lists enrollment of 192 participants and a completed status. The start is recorded as 2008-01 and primary completion as 2011-06. The sponsor is Children's Hospital Medical Center, Cincinnati. These administrative details describe the registered study; they do not supply outcome estimates.

Participants were assigned to one of three prenatal vitamin D3 regimens. Each group received a prenatal vitamin containing 400 IU of cholecalciferol. The comparison group also received a placebo tablet containing 0 IU. The other groups received tablets containing 1600 IU or 3600 IU of cholecalciferol; the registry labels the groups 2000 IU and 4000 IU, respectively. The record does not report details of the randomization sequence, allocation concealment, or how masking was maintained.

The primary outcome was maternal serum and neonatal serum 25-hydroxyvitamin D, measured at multiple specified stages from pregnancy through birth. Secondary outcomes concerned newborn crown-heel length, head circumference at birth, and birthweight. Because the primary outcome spans several time points and maternal and neonatal measurements, a single numerical comparison would not capture all of the registered outcome information. The registry record does not give outcome values, analysis estimates, or results by arm. It also does not report the protocol’s sample-size justification, detailed analysis plan, or whether additional analyses were conducted.

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

Analysis population for the primary outcome, as defined in the registry: Intention to treat analysis.

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 Maternal Serum and Neonatal Serum 25-hydroxyvitamin D Measurement, measured over 12, 16, 28 weeks and at maternal delivery and neonatal birth.

The primary endpoint concerns serum 25-hydroxyvitamin D, a blood measure used to assess vitamin D status. The registry specifies maternal measurements at 12, 16, and 28 weeks during pregnancy and at delivery, along with cord blood or neonatal serum measurement at birth. The unit is nmol/L, and the registered summary parameter is the mean with standard error as the stated measure of dispersion.

Following levels across pregnancy and at delivery can describe maternal status at different stages, while the newborn measurement addresses vitamin D status at birth. This makes the endpoint relevant to the trial’s stated question about achieving or maintaining sufficient vitamin D levels in mothers and infants. It is a biomarker outcome; it is not itself a direct measure of infant growth or a clinical diagnosis.

The registry also lists newborn crown-heel length, head circumference at birth, and birthweight as secondary outcomes. These are distinct from the primary blood measure and should not be treated as substitutes for it. Numerical values, standard errors, and comparisons between the groups for the primary endpoint are not reported in the registry record. Consequently, the endpoint’s measurement schedule and intended meaning can be described, but its observed results cannot be interpreted from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the mean describe?

The primary outcome is a continuous measurement reported in nmol/L. A mean summarizes the average measured level in a group at a particular assessment. It can provide a compact description of the group’s values, but it does not show how widely individual measurements vary or whether every participant had a similar value. Here, the registry specifies means and standard errors as the intended summary, but it does not report those values.

A comparison of group means would describe an average difference between regimens at a specified time point. It would not, by itself, show the full distribution of individual values, establish why any difference arose, or answer every question about vitamin D status. Since the registry record contains no numerical mean or treatment contrast, no such comparison can be interpreted from it.

What does a standard error convey?

As a general statistical explanation, a standard error describes the precision of an estimated quantity, such as a sample mean. It is not the same as the spread of individual observations. A standard error is useful alongside a mean because it helps readers judge how uncertain the estimated group average may be. It does not describe the range of values among participants.

Confidence intervals are another general way to communicate uncertainty around an estimate. A confidence interval gives a range of values compatible with the data under the method used. Its width reflects the estimate’s precision, while its relation to a relevant null value can inform interpretation of a comparison. The registry record does not report confidence intervals or treatment-effect estimates for the primary outcome, so no interval-based interpretation is available.

Why does the measurement schedule matter?

The outcome schedule includes several maternal assessments and a newborn assessment. Repeated measurements can describe how a measure changes over time, but they are not interchangeable observations. A between-group contrast at 12 weeks addresses a different point in the course of pregnancy from a contrast at delivery. The neonatal measure also concerns a different population and biological time point from the maternal measures.

As a general statistical consideration, multiple measurements create choices about which contrasts to emphasize and how to account for repeated observations. Repeated values from the same participant may be related, so an analysis that treats them as independent can misrepresent uncertainty. The registry record does not report the model used to analyze repeated measurements, whether the correlation among measurements was considered, or how the primary comparison was defined across time points.

What can randomization and masking contribute?

Random allocation is intended to make treatment groups comparable, on average, with respect to factors that could affect outcomes. It does not ensure identical groups in a particular trial, especially in characteristics not measured or reported. The record identifies randomization but does not describe sequence generation or allocation concealment, so those implementation details are not reported in the registry record.

Double masking means the registry classifies the study as masked at two levels, but it does not identify which participants or study personnel were masked or explain how masking was maintained. In general, masking can reduce the influence of expectations on care, reporting, or assessment. The designation alone does not establish that masking remained effective throughout the study.

How should planning calculations be distinguished from findings?

Sample-size planning asks how many participants might be needed to detect an effect under stated assumptions. Such a calculation depends on assumptions about the effect, variability, significance level, allocation, and statistical method. It is a planning exercise, not an observed trial result. A calculation based on an observed effect is also not observed power and does not replace a confidence interval or a direct report of the outcome estimate.

The registry record does not report the trial’s sample-size justification. It also does not provide numerical outcome estimates from which the trial’s observed differences could be interpreted. Therefore, planning illustrations should not be read as evidence that a treatment effect was found or that the study had a particular degree of power for its actual findings. The reported enrollment of 192 is a design and registration detail; it does not establish how many participants contributed to each endpoint assessment.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome includes maternal measurements at several pregnancy time points and at delivery, as well as a neonatal measurement at birth. The registry also lists newborn crown-heel length, head circumference, and birthweight as secondary outcomes. Examining multiple outcomes and time points raises a general multiplicity issue: the more comparisons considered, the greater the chance that some may appear notable by chance if no adjustment or prespecified hierarchy is used.

Whether the trial adjusted for multiple comparisons, designated a single primary time point, or used a hierarchy of tests is not reported in the registry record. The record also does not report a statistical analysis plan detailing how repeated measures were modeled or how outcomes were prioritized.

The primary outcome description identifies an intention-to-treat analysis population. In general, intention-to-treat analysis aims to analyze participants according to their randomized assignment, regardless of treatment received after assignment. The registry does not provide the analysis dataset, participant flow, or details of how this population was implemented for each outcome and time point.

Missing-data methods, reasons for missing measurements, and the number of participants with available outcome data are not reported in the registry record. Those details matter because incomplete follow-up can affect both the precision and interpretation of estimates, particularly when outcome collection occurs repeatedly. Without the participant-level flow and analysis details, it is not possible to assess whether missingness differed between groups or how it was handled.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists three groups, labeled 400 IU, 2000 IU, and 4000 IU. The numbers at risk for serious adverse events are 64, 65, and 63, respectively. The numbers at risk for other adverse events are also 64, 65, and 63. The registry records zero affected participants for serious events and zero for other events in each group.

These entries mean that the registry reports no affected participants in the listed event categories for the stated groups. They do not provide event descriptions or a detailed account of how events were collected, monitored, or classified. The serious-event terms list is empty. Death counts are not reported in the registry record.

Zero recorded affected participants should not be interpreted as proof that no safety issue occurred under any definition or throughout every aspect of follow-up. The record does not provide further context about exposure duration, completeness of event reporting, or the timing of safety assessments. The figures are best read as the safety counts entered in the registry, with the limitations of the accompanying reporting.

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

The registry record documents a randomized, double-masked comparison of prenatal vitamin D3 regimens and identifies maternal and neonatal 25-hydroxyvitamin D as the primary outcome. It also identifies infant size measures as secondary outcomes. Those details clarify what the trial set out to evaluate, but they do not reveal the findings.

Numerical outcome results are not reported in the registry record. As a result, it is not possible to determine from this information whether the groups had different mean vitamin D levels, how large any difference was, or how uncertain an estimate might be. Nor can the record establish whether any difference varied across the maternal assessment times or the newborn measurement. Results for the secondary outcomes are also not reported.

The registry’s statement of purpose is not evidence that a regimen achieved or maintained a particular level, and the trial’s completed status is not a result. The listed safety counts are limited to the adverse-event entries described in the record; they do not answer the efficacy question or provide a complete account of safety.

More broadly, a registered trial design and a stated endpoint should be distinguished from a report of comparative results. Interpretation of treatment effects would require outcome estimates, uncertainty measures, participant flow, and analysis details. These items are not reported in the registry record, so conclusions about the direction, magnitude, or precision of any treatment effect would go beyond the documented information.

13. Why This Trial Matters Statistically

This trial illustrates a statistical distinction between a clearly described research question and a report of results. The registry identifies randomized assignment, masking, three vitamin D3 regimens, a continuous primary outcome, and a schedule of maternal and neonatal assessments. Those details establish the intended framework for comparison. Without numerical findings, however, they cannot answer whether the groups differed.

The measurement schedule also highlights how an outcome can contain several related questions. Maternal levels during pregnancy, levels at delivery, and neonatal levels at birth each have a distinct interpretation. Any complete statistical account would need to make clear which comparisons were prespecified, how repeated measurements were handled, and how uncertainty was expressed. Those analysis details are not reported in the registry record.

The record’s enrollment and adverse-event entries are informative in their own limited roles, but neither substitutes for comparative outcome estimates. Enrollment does not show how many participants contributed data to each assessment, and zero affected participants in the listed event categories does not provide an estimate of vitamin D levels or infant growth. Keeping design information, outcome findings, and safety reporting distinct is essential when reading a clinical trial registry.

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 main limitation for interpreting this trial from the registry record is that numerical primary and secondary outcome results are not reported. No group means, standard errors, treatment contrasts, confidence intervals, or test results are available for maternal or neonatal 25-hydroxyvitamin D. Results for newborn length, head circumference, and birthweight are also not reported. Consequently, the registry record cannot establish the size, direction, or precision of treatment differences.

The primary outcome spans several time points and includes maternal and neonatal measurements. The record does not report how these measurements were combined or prioritized in the analysis, which comparisons were prespecified, or whether multiplicity was addressed. The statistical model for repeated measurements is not reported in the registry record.

Participant flow and outcome-specific sample counts are not reported, nor are reasons for missing measurements or methods used to handle missing data. Although the outcome description specifies an intention-to-treat analysis population, details of its implementation are not reported. The registry also does not report eligibility criteria, baseline participant characteristics, randomization-sequence methods, allocation concealment, or details of how masking was maintained.

Finally, the adverse-event entries provide counts but little contextual detail. The record does not report death counts, and the serious-event terms list is empty. These limitations constrain interpretation of both the trial’s comparative findings and the completeness of its safety information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Controlled Trial of Prenatal Vitamin D3 Supplementation to Prevent Vitamin D Deficiency in Mothers and Their Infants — NCT00610688.
• Registry record last updated 2021-10-19; status last verified 2021-09.
• Results first posted 2013-06-07.
• 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

NCT00610688 is a completed phase 3, randomized, double-masked, parallel-group trial sponsored by Children's Hospital Medical Center, Cincinnati. The registry lists enrollment of 192, a start of 2008-01, and primary completion of 2011-06.

The three regimens paired a prenatal vitamin containing 400 IU of vitamin D3 with either placebo or an additional vitamin D3 tablet. The groups are labeled 400 IU, 2000 IU, and 4000 IU. The primary outcome was maternal and neonatal serum 25-hydroxyvitamin D, with measurements planned during pregnancy, at delivery, and at birth. Secondary outcomes included newborn length, head circumference, and birthweight.

Numerical efficacy results, outcome-specific participant counts, and detailed analysis methods are not reported in the registry record. The adverse-event entries list zero affected participants in each group for serious and other events; death counts are not reported.