Intravenous Iron for Iron-deficiency Anemia in Pregnancy: a Randomized Controlled Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Intravenous Iron for Iron-deficiency Anemia in Pregnancy: a Randomized Controlled Trial (NCT03438227), a randomized phase 4 study. The primary outcome is Maternal Anemia at Delivery.

2. Clinical Question

The question addresses whether the two treatment protocols were associated with different observed rates of maternal anemia at delivery in this trial. It does not, by itself, establish which approach should be used in other settings or for people who would not have met the trial’s eligibility criteria. Those criteria and the clinical reasons for assigning the oral group to continue treatment are not reported in the registry record.

3. Trial Design

This was a randomized, double-masked, parallel-group phase 4 trial listed as completed. The registry reports enrollment of 38 and gives a study start date of 2018-04-15 and a primary completion date of 2019-12-31. The sponsor was Indiana University. The listed conditions were iron-deficiency anemia of pregnancy and iron malabsorption.

Participants were assigned to intravenous iron dextran infusion or oral ferrous sulfate supplementation. The intravenous protocol described a single 1000mg dose given as an inpatient, with fetal monitoring before, during, and after the infusion. The oral group continued ferrous sulfate 325mg, one to three tablets daily, with the final dose determined by the obstetric provider. The registry record does not report further details about the randomization sequence, allocation concealment, or how masking was maintained.

The primary outcome was the number of participants with maternal hemoglobin <11g/dl at delivery. The secondary outcomes included maternal hemoglobin and ferritin at delivery, hemoglobin below 10g/dl at delivery, medication adverse events, blood transfusion, mode of delivery, gestational age at delivery, and birth weight. The posted secondary results cover 13 outcomes. Their timing and definitions vary, so they should not be treated as interchangeable measures of one underlying effect.

The enrollment figure is not the same as the number contributing data to every outcome. For the primary result, the registry reports an outcome denominator of 10 in the intravenous group and 13 in the oral group. Reasons that these denominators differ from overall enrollment, and the analysis population definition, are not reported in the registry record. The original sample-size justification, planned interim analyses, and detailed statistical analysis plan are also not 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.

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 Maternal Anemia at Delivery, measured over At delivery.

The primary endpoint counts participants whose maternal hemoglobin was <11g/dl at delivery. It is recorded as a participant count, with the assessment timeframe specified as at delivery. The endpoint therefore represents a threshold-based classification: each participant either meets the stated hemoglobin criterion or does not. It is not the same as comparing average hemoglobin values, because a threshold count does not show how far an individual’s value lies above or below the cutoff.

A threshold outcome can be clinically interpretable because it describes how many participants met a defined criterion at a particular time. Comparing the group counts can indicate whether the observed frequency of that criterion differed between the assigned protocols. The registry also posts maternal hemoglobin as a continuous secondary outcome, which gives complementary information about the distribution of measured values rather than only whether the cutoff was crossed.

The primary outcome is reported for 10 participants in the intravenous group and 13 in the oral group. The registry gives 4 participants with the endpoint in the intravenous group and 11 in the oral group. These counts describe the analyzed outcome data; they do not explain why some enrolled participants are absent from those denominators. Missing-data handling and the relationship between the outcome population and the randomized population are not reported in the registry record.

7. Results Posted in the Registry

• Oral Ferrous Sulfate Supplementation: 84.6% (11/13) versus 40.0% (4/10) on control; risk difference 44.6 percentage points (95% CI 8.5 to 80.8), risk ratio 2.12 (0.96–4.68); unadjusted two-proportion z-test p = 0.026.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Maternal Hemoglobin at Delivery

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Oral Ferrous Sulfate Supplementation: mean 9.90 versus 11.00 on control; difference -1.10 (95% CI -1.84 to -0.36), standardized effect d = -1.16; z-test p = 0.004.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Oral Ferrous Sulfate Supplementation than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Maternal Hemoglobin Below 10g/dl at Delivery

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Oral Ferrous Sulfate Supplementation: 53.8% (7/13) versus 10.0% (1/10) on control; risk difference 43.8 percentage points (95% CI 11.0 to 76.7), risk ratio 5.38 (0.78–36.96); unadjusted two-proportion z-test p = 0.029.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Oral Ferrous Sulfate Supplementation than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Maternal Ferritin at Delivery

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Oral Ferrous Sulfate Supplementation: mean 26.60 versus 129.80 on control; difference -103.20 (95% CI -176.27 to -30.13), standardized effect d = -1.33; z-test p = 0.006.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Oral Ferrous Sulfate Supplementation than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes cover related but distinct aspects of maternal and perinatal care. The posted pattern for maternal hemoglobin measures is directionally consistent with the primary count outcome: the intravenous group’s mean hemoglobin was higher, and fewer participants had hemoglobin below 10g/dl at delivery. Ferritin also differed in its posted group summaries. Other listed outcomes concern adverse events, transfusion, delivery, gestational age, and birth weight, but the available summary does not support treating all of these as measures of the same treatment effect.

Secondary results can add context to a primary finding by showing whether related measurements tell a coherent story, but they do not replace the prespecified primary outcome. Each outcome may have a different definition, measurement scale, denominator, and vulnerability to missing data. The registry record does not report whether the secondary outcomes were prespecified in a hierarchy or whether particular comparisons were intended to be confirmatory.

Several outcomes are examined, and no adjustment for multiple comparisons is reported in the registry record. When many comparisons are made, the chance of obtaining at least one apparently unusual result can increase, even if all comparisons are null in the underlying population. Unadjusted secondary p-values therefore carry less weight than a single prespecified primary analysis and should be treated as exploratory evidence rather than independent confirmation. The small outcome denominators also mean that estimates can be unstable. Taken together, the secondary results may inform interpretation of the primary endpoint, but they do not remove uncertainty about the effect’s size or generalizability.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Maternal Hemoglobin at Delivery
• Number of Participants With Medication Adverse Events
• Maternal Hemoglobin Below 10g/dl at Delivery
• Maternal Ferritin at Delivery
• Number of Participants Who Received Blood Transfusion
• Mode of Delivery
• Gestational Age at Delivery
• Birth Weight

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary: a participant either had maternal hemoglobin <11g/dl at delivery or did not. The posted group counts can be expressed as event proportions, and the recalculation compares those proportions using a risk difference. Here, the difference is oriented as oral ferrous sulfate minus intravenous iron dextran. A positive risk difference therefore means that the observed event proportion was greater in the oral group. It is an absolute contrast in proportions, not a relative measure.

What does a risk difference convey?

A risk difference retains the outcome’s original scale: the difference between the proportions meeting the endpoint in the two groups. It can be interpreted without converting the result into a ratio. Its value depends on the observed rates in both groups, and it does not describe how likely an outcome is for every individual participant. In a small trial, the estimate may be imprecise because each observed outcome contributes substantially to the group proportions.

The posted comparison also includes relative measures, but the primary interpretation can remain centered on the absolute contrast and its interval. A relative risk compares proportions as a ratio; an odds ratio compares odds rather than proportions. These measures answer different descriptive questions and may appear especially large or unstable when the event is common or the underlying counts are sparse. They should not be treated as interchangeable with a risk difference.

How should the p-values be read?

The registry’s primary analysis is labeled Chi-squared and reports p = 0.039. The recalculated unadjusted test reports p = 0.026. A p-value measures the compatibility of observed data with a null hypothesis under the assumptions of a chosen test. It is not the probability that the null hypothesis is true, and it does not measure the clinical importance of the observed contrast. The p-value also does not quantify uncertainty in the effect size as directly as an interval does.

Different tests can produce different p-values because they use different procedures and assumptions. With limited counts, the choice of test can matter. The registry record identifies the sponsor’s primary test as Chi-squared, while the recalculation is a simple unadjusted comparison of posted summary statistics. The record does not report a detailed statistical analysis plan explaining the choice of test or any adjustments.

What does the continuous-outcome comparison add?

Maternal hemoglobin at delivery is posted as a mean with a standard deviation for each group. A mean difference compares the group averages, with the reported direction for the oral-minus-intravenous contrast. This continuous outcome uses the measured hemoglobin values rather than reducing them to whether each value crossed the primary cutoff. The reported recalculated mean difference is -1.1 g/dL, with an interval from -1.839 to -0.361. The registry reports a two-sided t-test with p = 0.019; the unadjusted recalculation gives p = 0.004.

Ferritin is also reported as a mean and standard deviation. Variation is much larger in the intravenous group than in the oral group in the posted summary statistics. When variation differs substantially across groups, a pooled-variance comparison may not represent the data well; a method that does not rely on equal variances can be preferable in general. The registry labels its analysis as a two-sided t-test and reports p = 0.19, while the unadjusted recalculation reports p = 0.006. The record does not report which variance assumptions or specific t-test implementation were used by the sponsor, so these results should be kept distinct rather than treated as equivalent.

For the secondary binary outcome of hemoglobin below 10g/dl at delivery, the registry reports Fisher Exact with p = 0.029, and the unadjusted recalculation also reports p = 0.029. Fisher’s exact test is a method for comparing categorical outcomes that uses the observed counts directly. General statistical practice often favors it when counts are sparse, but the registry record does not describe the rationale for selecting tests.

Why are unadjusted comparisons limited?

The recalculated values are simple, unadjusted comparisons based on the posted summary statistics. They do not account for covariates, stratification, missing outcomes, or multiple comparisons. Whether any such features were part of the original analysis is not reported in the registry record. Recalculation can help readers understand the posted group summaries, but it cannot reproduce an analysis whose details or participant-level data are unavailable.

The reported tests and recalculations are not evidence of observed power. Power is a design concept concerning the chance of detecting a specified effect under stated assumptions. The planning illustrations use hypothetical effects based on the observed differences and are not a substitute for a prespecified design calculation. General statistical interpretation should therefore emphasize the effect estimates, uncertainty, study context, and limitations together, rather than treating any single test result as decisive.

11. Confidence Intervals and Precision

The primary risk-difference interval runs from 0.085 to 0.808 around an estimate of 0.446, for the oral-minus-intravenous contrast. It indicates that the data are compatible with a range of possible absolute differences. The estimate is positive across the reported interval, but the range is broad relative to the point estimate. This means the direction is more clearly represented than the exact magnitude in this small set of outcome data.

An interval is useful because it makes uncertainty in an estimated effect visible. It is not a guarantee that the true effect lies within its endpoints, nor does it represent a range of outcomes for individual participants. The registry record does not state the confidence level for the recalculated intervals, so no confidence percentage should be inferred from the posted values alone.

The continuous hemoglobin comparison has a recalculated mean difference of -1.1 g/dL, with an interval from -1.839 to -0.361. The interval is entirely below zero for the stated oral-minus-intravenous direction. The recalculated ferritin mean difference is -103.2 μg/L, with an interval from -176.3 to -30.13, also below zero for the same group ordering. The two secondary intervals describe different outcomes and scales; neither should be interpreted as a direct measure of the primary endpoint.

For hemoglobin below 10g/dl, the recalculated risk difference is 0.439, with an interval from 0.110 to 0.767. This interval is also for oral minus intravenous. The breadth of these intervals underscores the limited precision available from the posted outcome denominators. An interval’s location and width should be considered alongside the group counts and the analysis method, not replaced by a simple significant-or-not label.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size illustrations express the planned number of participants per arm, not a total across both arms and not a total number of events. They are based on a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. These are planning assumptions for illustrations; the original design assumptions for the trial are not reported in the registry record.

The 80% power column gives the illustrated number of participants per arm for a design with an 80% chance of detecting the specified effect under those assumptions. The 90% power column gives the corresponding number per arm for a design with a 90% chance. For example, for planning for 100% of the observed primary effect, the illustration lists 18 participants per arm for 80% power and 23 participants per arm for 90% power. Planning for 75% of the observed effect lists 34 participants per arm for 80% power and 44 participants per arm for 90% power. Planning for 50% of the observed effect lists 78 participants per arm for 80% power and 104 participants per arm for 90% power.

The pattern is expected: smaller effects require more participants to detect under otherwise unchanged assumptions. These figures are hypothetical planning illustrations derived from the observed effect, not the trial’s original design calculation. They are not observed power.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.400; treatment proportion p₁ = 0.846; average p̄ = 0.623.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6853 = 1.3433.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6084 = 0.5121.
4. n = (1.3433 + 0.5121)² / (0.4462)² = 17.3, rounded up to 18 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.4                          # control proportion
p1 <- 0.846153846153846                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3438227)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 18 (80% power), 23 (90% power)
 75% of observed effect: n per arm = 34 (80% power), 44 (90% power)
 50% of observed effect: n per arm = 78 (80% power), 104 (90% power)
power.prop.test: 17.3 
Simulated power at n = 18 per arm: 0.842 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

For the primary maternal anemia outcome, the registry reports a Chi-squared analysis with p = 0.039. The simple unadjusted recalculation from the posted counts gives p = 0.026 and a risk difference of 0.446, with an interval from 0.085 to 0.808. The registry’s analysis and the recalculation are distinct results: the former is the sponsor-reported test, while the latter is an unadjusted comparison computed from the posted summary statistics.

The record also reports sponsor analyses for the secondary outcomes. For maternal hemoglobin at delivery, it reports a two-sided t-test with p = 0.019, compared with an unadjusted recalculated p = 0.004. For hemoglobin below 10g/dl, the reported Fisher Exact p-value and recalculated p-value are both 0.029. For maternal ferritin, the sponsor-reported two-sided t-test gives p = 0.19, whereas the unadjusted recalculation gives p = 0.006.

These comparisons do not establish why the values differ. The registry record does not provide the sponsor’s detailed analysis code, assumptions, missing-data procedures, or full statistical analysis plan. The recalculations use posted summary statistics and should not be mistaken for a reproduction of the sponsor’s analysis. The record does not flag a discrepancy, but readers should still keep the sponsor-reported analyses and unadjusted recalculations clearly labeled rather than selecting whichever p-value appears more favorable.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and 13 posted secondary outcomes. It does not report a multiplicity adjustment, a hierarchy for testing secondary outcomes, or a detailed plan for interpreting multiple comparisons. Without such a plan, secondary p-values should be viewed cautiously: testing many outcomes can increase the chance of at least one apparently notable result. The posted secondary comparisons are therefore not equivalent to a set of independently confirmatory tests.

Missing-data handling is not reported in the registry record. The primary outcome is posted for 10 participants in the intravenous arm and 13 in the oral arm, while overall enrollment is reported as 38. The reason for the difference between enrollment and these outcome denominators is not stated. The record does not explain whether data were unavailable, participants were excluded from an analysis, or another process produced the outcome populations. No assumptions about missing outcomes can be verified from the posted summary.

The analysis population is also not reported in sufficient detail to determine whether the posted comparisons follow an intention-to-treat, per-protocol, or another approach. The registry does not describe a prespecified plan for covariate adjustment, handling protocol deviations, or interim analyses. These details matter because they influence which participants contribute to an estimate and how the reported uncertainty should be interpreted.

These omissions do not invalidate the reported counts, but they limit assessment of the analysis process and the robustness of the results. The posted group summaries can be described as reported, while conclusions about missingness, analysis populations, or multiplicity control should remain open because those methods are not reported in the registry record.

16. 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 0% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse event figures report zero affected participants in both groups: 0 of 10 at risk in the intravenous iron dextran group and 0 of 13 at risk in the oral ferrous sulfate group. Deaths are also reported as 0 in each group. For other adverse events, the registry reports 3 of 10 in the intravenous group and 3 of 13 in the oral group.

These are counts over the risk denominators recorded for the safety outcomes. A finding of zero reported serious adverse events in these groups does not establish that serious events cannot occur, and the small denominators limit how much can be concluded about uncommon harms. The registry’s serious adverse event terms are not listed, and details about event type, severity grading, timing, or attribution are not reported in the registry record.

The equal count of other events should not be read as equal risk: the group denominators differ, and the record does not provide an adjusted safety comparison. These summaries are descriptive and do not resolve comparative safety beyond the events and participants recorded.

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

The primary result describes a higher observed count of maternal hemoglobin <11g/dl at delivery in the oral group than in the intravenous group among participants with posted outcome data. The recalculated risk difference and its interval express the size and uncertainty of that comparison. The registry’s Chi-squared result is also reported, and it should be distinguished from the unadjusted recalculation.

This finding does not establish that intravenous iron is appropriate for every pregnant person with iron-deficiency anemia, or that oral iron is inappropriate. The trial compares specified protocols in the enrolled population, and its outcome denominators are limited. Eligibility criteria, participant characteristics beyond the listed conditions, and the reasons that some enrolled participants do not appear in the primary outcome denominator are not reported in the registry record.

The primary endpoint is a threshold measure at delivery. It does not show the full course of hemoglobin during pregnancy, explain the importance of each participant’s value, or directly answer every question about maternal and infant outcomes. The secondary outcomes provide additional measurements, but multiple comparisons and incomplete reporting of analysis methods make them less definitive. The safety counts are also too limited to rule out uncommon events.

Statistical significance is not the same as clinical importance, and a p-value does not indicate the probability that a treatment effect is real. The interval and group counts help convey the uncertainty, while the design and reporting limitations constrain how broadly the findings can be applied. The results are best understood as evidence from this randomized comparison, not as a complete basis for treatment decisions or a guarantee of outcomes outside the trial.

18. Why This Trial Matters Statistically

This trial raises a practical statistical question: how should a small randomized comparison be interpreted when the primary endpoint is a count, the posted outcome denominators are limited, and secondary outcomes span several clinical domains? The result illustrates why reporting the event counts, an absolute effect estimate, an interval, and the sponsor’s test together is more informative than relying on a p-value alone.

It also shows the value of distinguishing a threshold endpoint from a continuous measurement. Maternal anemia at delivery is represented as a count meeting a stated cutoff, while mean hemoglobin and ferritin describe group averages and variability. These outcomes can complement one another, but each answers a different question and may have different statistical properties.

Comparing sponsor-reported analyses with simple unadjusted recalculations can help readers see how conclusions depend on the analysis method. The values should not be silently combined, and an unadjusted reconstruction cannot replace analysis details that are not reported. This is particularly relevant for secondary outcomes, where multiple testing and incomplete methodological information weaken the strength of isolated findings.

Finally, the planning illustrations make clear that sample-size needs depend on the effect size a future study aims to detect and the desired power. They are not evidence about the power achieved in this trial. The registry does not report the original design assumptions, so the illustrative calculations should be kept separate from claims about the trial’s planning or ability to detect its true effect.

19. 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 posted outcome denominators are smaller than the reported enrollment, and the registry record does not explain why. Without information on missing outcomes or the analysis population, it is not possible to assess whether the posted comparisons represent all randomized participants or whether missingness could have influenced the results.

The study’s enrollment and outcome counts are limited, leaving substantial uncertainty around effect sizes and little information about uncommon safety events. The record reports no serious adverse events in either group, but those counts cannot rule out rare harms. Event descriptions and further safety-analysis details are not reported in the registry record.

The registry does not report the original sample-size calculation, detailed statistical analysis plan, multiplicity strategy, interim analyses, or important randomization and masking procedures. This limits assessment of whether the posted analyses match the intended design and how secondary comparisons were selected or interpreted. The differing sponsor-reported and recalculated p-values for some outcomes further underline the need for methodological detail; they do not, by themselves, identify which procedural choice caused the difference.

Generalizability is also uncertain because participant characteristics and eligibility details are not reported beyond the listed conditions and the pregnancy context. The trial compares a particular intravenous infusion protocol with continued oral supplementation at a dose whose final amount was determined by the obstetric provider. Results should not automatically be extended to other populations, protocols, or care settings.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Intravenous Iron for Iron-deficiency Anemia in Pregnancy: a Randomized Controlled Trial — NCT03438227.
• Registry record last updated 2024-06-11; status last verified 2024-05.
• Results first posted 2024-06-11.
• 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.

23. Record Summary

NCT03438227 is a completed, randomized, double-masked, parallel-group phase 4 trial sponsored by Indiana University. It reports enrollment of 38 and compares a single intravenous iron dextran infusion with continued oral ferrous sulfate supplementation in pregnant women with iron-deficiency anemia.

The primary outcome was the number of participants with maternal hemoglobin <11g/dl at delivery. The registry reports 4 of 10 in the intravenous group and 11 of 13 in the oral group, with a Chi-squared p-value of 0.039. The unadjusted recalculation gives a risk difference of 0.446 for oral minus intravenous, with an interval from 0.085 to 0.808.

Secondary outcomes include maternal blood measures, safety, delivery, and birth outcomes. The registry does not report detailed missing-data methods, the analysis population, the original sample-size assumptions, or a multiplicity plan. The posted results describe this trial’s data and should be interpreted with those limitations in view.