The Impact of Distress on the IVF Outcome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Impact of Distress on the IVF Outcome (NCT01103973), a randomized na study. The primary outcome is Clinical Pregnancy Rates.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, controlled prospective study conducted at a private, academically affiliated infertility clinic. Its summary says women scheduled for a first IVF cycle were assigned using a computer-generated random numbers table to a ten-week mind/body program or control and followed for two IVF cycles. The record lists allocation as randomized and masking as none. It also labels the study model as single group, which does not align neatly with the description of two assigned groups; the registry record does not explain that classification.

The record lists enrollment as 143 and status as completed. The primary outcome results are presented separately for control and mind/body participants, with outcome denominators of 51 and 46, respectively. The record does not explain the relationship between enrollment and these outcome denominators, including whether missing outcome data or other exclusions account for the difference. The sponsor is Boston IVF. The recorded start and primary-completion dates are 2007-03 and 2009-09.

The primary outcome was clinical pregnancy rate, with the outcome timeframe listed as 1 year. The study summary describes follow-up across two IVF cycles, while the endpoint description defines clinical pregnancy using findings at 7 weeks gestation. The registry record does not clarify the timing of endpoint assessment across cycles or provide a fuller account of participant flow. No original statistical analysis plan, sample-size justification, or details of any interim analyses are reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: A total of 46 women withdrew or were ineligible for the study. The reasons for withdrawal were: 1) no longer eligible owing to no subsequent IVF cycle (15 patients); 2) too great a time commitment (15 patients); 3) noncompliance with study requirements (7 patients); 4) dislike of study tasks (6 patients); and 5) other (3 patients).

Overall Study

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 Clinical Pregnancy Rates, measured over 1 year.

The primary endpoint is clinical pregnancy rate, reported as a percentage of participants. The registry record defines a clinical pregnancy as the presence of a normal fetal heart rate and fetal size at 7 weeks gestation. The listed timeframe is 1 year. This makes the outcome a binary event for each participant: the defining pregnancy findings are either recorded or not recorded within the stated assessment framework.

In general, a binary pregnancy endpoint gives a direct countable outcome for comparing groups. A clearly stated clinical definition also helps distinguish the measured endpoint from broader concepts such as treatment continuation, pregnancy testing, or later pregnancy outcomes. The record does not provide additional detail about how the pregnancy findings were assessed, who assessed them, or how outcomes across the two IVF cycles were combined for the primary analysis. Those details should not be inferred from the endpoint label alone.

The registry record lists clinical pregnancy rate as the primary outcome and separately identifies a pregnancy-rate outcome based on psychological status assessed by the Beck Depression Inventory as a secondary outcome. The posted primary results concern the clinical pregnancy endpoint. They do not, by themselves, provide information about other reproductive outcomes or the timing and durability of pregnancy beyond the stated definition.

7. Results Posted in the Registry

• Mind/Body Program: 52.2% (24/46) versus 19.6% (10/51) on control; risk difference 32.6 percentage points (95% CI 14.5 to 50.7), risk ratio 2.66 (1.43–4.95); unadjusted two-proportion z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record presents a binary primary outcome: clinical pregnancy, defined by specified findings at 7 weeks gestation. For each group, it reports a percentage of participants with the event. A group percentage describes the observed frequency of the endpoint within that group; it does not by itself describe the uncertainty around that frequency or the certainty of a between-group contrast.

What does the group comparison measure?

A risk difference compares the event probabilities by subtracting one group’s probability from the other’s. It is an absolute contrast, expressed on the probability scale. A risk ratio divides one group’s event probability by the other’s and describes a relative contrast. An odds ratio compares odds rather than probabilities. Odds and probabilities are related but not identical, so an odds ratio should not be read as though it were a risk ratio, particularly when an outcome is not rare.

The comparison record includes a risk-difference estimate and confidence interval, as well as risk-ratio and odds-ratio estimates with intervals. These measures can help readers understand the direction and scale of the reported contrast. The arm percentages and the comparison estimates need not have the same displayed precision because they are different summaries. The registry record does not state a covariate-adjustment strategy for these comparisons.

What does the p-value say?

The registry record reports an unadjusted p-value of <0.001. In general, a p-value describes how incompatible the observed data, or data more extreme, would be with a specified null model if that model and the test assumptions held. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. The word “unadjusted” indicates that the reported value is not presented as adjusted for multiple comparisons. The registry record does not give further details of the test used to obtain it.

A small p-value does not remove uncertainty about the estimated effect. Effect estimates and their confidence intervals address magnitude and precision, while the p-value addresses compatibility with a null model under a test framework. Interpretation also depends on the quality of outcome ascertainment, completeness of follow-up, and the analysis population. The registry record does not report enough detail to evaluate all of those elements.

Why does randomization matter?

In general, random assignment aims to reduce systematic differences between groups at the start of a trial. It does not guarantee that the groups are identical, especially in a study with limited numbers of observed outcomes. The summary says computer-generated random numbers were used, but the registry record does not report allocation concealment, baseline characteristics, or a detailed account of how assignment was implemented. Masking is listed as none. For a behavioral program, participants would know the assigned program, but the record does not state whether outcome assessors were masked.

The record labels the model as single group while describing randomized assignment to a mind/body program and a control group. This inconsistency in the registry classification should be kept distinct from the reported two-group outcome results; no explanation of the classification is reported.

What role does over-dispersion have?

Over-dispersion is a general concern in some count-data models when observed variability exceeds what a simple model assumes. It is not directly relevant to the basic binary pregnancy percentages as reported, and the registry record does not describe a count-data model or an over-dispersion adjustment. The endpoint is not a count of repeated events in the posted primary results.

Overall, the registry record gives a group comparison and an unadjusted p-value, but does not report the full statistical analysis plan, the exact test procedure, covariate adjustments, or detailed analysis-population rules. These omissions limit independent assessment of how the reported inferential results were generated.

10. Confidence Intervals and Precision

Precision concerns how narrowly the data locate an effect estimate. A confidence interval gives a range of values compatible with the data and the statistical procedure used, under the model assumptions. It is not a guarantee that the true effect lies within the interval, nor does it account for sources of bias that the analysis did not address.

The registry comparison reports intervals for the risk difference, risk ratio, and odds ratio. The interval around a risk difference is on the absolute probability scale; the intervals for the risk ratio and odds ratio are on relative scales. Because these measures use different scales, the widths and endpoints cannot be compared as if they conveyed the same quantity. The posted intervals indicate statistical uncertainty around their corresponding estimates, but precision alone does not establish the validity or generalizability of the comparison.

The arm percentages are 20.0% for control and 52.0% for the mind/body program. The posted outcome denominators are 51 and 46, respectively. These outcome counts are modest in scale, so estimates from the trial may be sensitive to a small number of outcomes; this is a general property of estimates based on limited observations, not a claim about any unreported data. The registry record does not report a confidence interval for each group percentage.

The reported unadjusted p-value is <0.001, but a p-value alone does not show the precision of the estimated contrast. The comparison intervals provide additional information about uncertainty, while unreported details about missing outcomes, analysis populations, and model choice remain relevant to interpretation. The confidence intervals also do not capture uncertainty caused by limitations in reporting or possible differences between the study setting and other settings.

11. 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 figures are planning illustrations, not a report of the trial’s original design calculation. They are expressed as participants per arm, rather than as total event counts. The assumptions listed for the illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is specified as a fraction of the observed effect.

The column for 80% power gives the participants per arm in a hypothetical future study that would have an 80% chance of detecting the chosen effect under the stated assumptions, if that effect and the model assumptions were correct. The 90% power column gives the corresponding planning figure for a 90% chance. These are design targets, not statements about the probability that the observed result is true. This is not observed power.

Planning rows use the full observed effect and smaller fractions of that observed effect. A smaller target effect requires more participants per arm to achieve the same planned power under otherwise unchanged assumptions. The displayed figures therefore illustrate how planning needs can change when researchers aim to detect a less pronounced effect. They should not be treated as a recommendation without considering the intended study population, endpoint, analysis, and feasibility.

The original trial’s own sample-size assumptions and justification are not reported in the registry record. The planning calculations are explicitly based on the observed effect, rather than on a documented prospective design target. They cannot establish whether the original study was adequately planned, and they are not a retrospective measure of the chance that the trial detected an effect.

12. 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 = 0.196; treatment proportion p₁ = 0.522; average p̄ = 0.359.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6784 = 1.3296.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6381 = 0.5370.
4. n = (1.3296 + 0.5370)² / (0.3257)² = 32.9, rounded up to 33 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 <- 0.196078431372549                          # control proportion
p1 <- 0.521739130434783                          # 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(1103973)
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 = 33 (80% power), 44 (90% power)
 75% of observed effect: n per arm = 56 (80% power), 75 (90% power)
 50% of observed effect: n per arm = 118 (80% power), 157 (90% power)
power.prop.test: 32.9 
Simulated power at n = 33 per arm: 0.821 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry record identifies clinical pregnancy rate as the primary outcome and lists a secondary outcome concerning pregnancy rate based on psychological status assessed by the Beck Depression Inventory. It also reports two outcome measures and one posted secondary outcome. When a study examines more than one outcome, subgroup, or time point, the chance of at least one apparently notable result can increase. In general, a prespecified testing strategy or multiplicity adjustment may be used to address that issue.

No multiplicity strategy is reported in the registry record. The posted p-value is described as unadjusted, so it should not be read as a value corrected for testing across outcomes or other analyses. The record does not report a full statistical analysis plan or indicate whether the primary outcome and analysis were prespecified before results were known. No subgroup-analysis plan is reported.

The record lists no analysis records, while still posting primary outcome results and a group-comparison p-value. It does not explain the distinction between those registry entries. This reporting gap prevents a complete account of the analyses performed. The secondary outcome is named, but the registry record does not provide its results or describe how psychological status was categorized or incorporated into the analysis.

Missing-data handling and analysis-population definitions are also not reported in the registry record. The overall enrollment is 143, whereas the posted primary outcome denominators are 51 for control and 46 for the mind/body program. The record does not state whether these results use an intention-to-treat population, a per-protocol population, or another analysis set; nor does it explain exclusions, withdrawals, or missing outcome assessments. Without those details, the extent to which the posted results reflect all randomized participants cannot be assessed from the registry record.

These omissions do not establish that particular analyses or procedures were or were not used. They mean that the registry record does not document them, and readers should avoid assuming a multiplicity correction, a missing-data method, or a specific analysis population.

14. 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 record lists zero serious adverse events among 51 participants at risk in the control group and among 46 participants at risk in the mind/body group. It also lists zero other adverse events in each group, using the same respective at-risk counts. Death counts are recorded as not reported.

These entries describe what the registry record reports; they do not establish that no events occurred outside the recorded definitions, observation period, or reporting process. The record does not give detailed adverse-event definitions, collection procedures, severity criteria, or a safety follow-up period distinct from the study follow-up. It also does not list any specific serious adverse-event terms.

Zero recorded events in the posted categories should therefore be interpreted as a registry reporting result, not as proof that the intervention or study procedures carried no risk. The adverse-event figures do not address the effectiveness of either group assignment, and they do not replace assessment of the study’s event-collection methods.

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

The registry record reports clinical pregnancy percentages of 20.0% in the control group and 52.0% in the mind/body program group. It also reports an unadjusted p-value of <0.001. These are the posted data for the primary endpoint and indicate a difference between the observed group percentages. The comparison estimates and their intervals provide additional descriptions of the group contrast and its statistical uncertainty.

Those findings do not, on their own, establish why the percentages differed. Random assignment is described, but the record does not provide baseline characteristics, details of allocation concealment, a full analysis plan, or an account of missing outcomes. The difference between enrollment and the posted outcome denominators is not explained. The record also lists the model as single group despite describing two randomized groups. These gaps make it harder to evaluate the full conduct and analysis of the trial from the registry record alone.

The endpoint is clinical pregnancy under the stated definition at 7 weeks gestation, with a timeframe listed as 1 year. It is not a report of every aspect of IVF outcome, and the posted result should not be generalized to unreported outcomes. The record does not provide the secondary outcome results for pregnancy rate based on psychological status assessed by the Beck Depression Inventory.

The results apply to the study as described: women age 40 and below scheduled for a first IVF cycle at a private, academically affiliated infertility clinic, assigned to a ten-week group program or the stated control arrangement. The registry record does not establish whether a similar contrast would be observed in other populations or settings. Statistical significance, effect size, precision, study conduct, and applicability are separate considerations. The reported comparison should be understood in the context of all of them, rather than as a standalone conclusion about treatment.

16. Why This Trial Matters Statistically

This trial illustrates how a behavioral intervention can be evaluated alongside a clinical outcome. The primary endpoint is not a distress score or program attendance; it is clinical pregnancy as defined by fetal heart rate and fetal size at 7 weeks gestation. That distinction matters because the intervention is psychological in content while the principal posted outcome is a clinical event.

The registry reports group percentages as well as several contrast measures and a p-value. Reading these together is important: percentages describe each group, risk differences and relative measures describe contrasts on different scales, confidence intervals convey uncertainty, and a p-value addresses compatibility with a null model under assumptions. No one statistic answers every question about magnitude, precision, or relevance.

Study design and reporting are equally important to interpretation. The summary describes random allocation, but the record does not provide details such as baseline characteristics, missing-data methods, or the analysis population. The enrollment figure and the outcome denominators are not reconciled. The single-group model label also sits uneasily alongside the two-group randomized description. These are not merely technical details: they affect a reader’s ability to trace how the reported outcome data arose.

The planning illustrations also show why effect assumptions matter in design. Figures based on the observed effect are not equivalent to a prospective sample-size justification, and smaller target effects require more participants per arm under the listed assumptions. The trial’s original design assumptions are not reported. Keeping this distinction clear prevents a retrospective planning illustration from being mistaken for evidence about the original design or the likelihood of detecting the observed result.

17. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

Several trial-specific reporting limitations affect interpretation. The registry record lists enrollment of 143, while the posted primary-outcome denominators are 51 in control and 46 in the mind/body group. It does not explain the difference, report participant flow, or specify whether the posted analysis includes all randomized participants. Missing outcome data and their handling are not reported.

The record’s study-model label is single group, although the summary describes randomization to a mind/body program or control and the results are reported by group. No explanation of this classification is reported. The record states that masking was none but does not clarify whether anyone involved in endpoint assessment was masked. It also does not provide baseline characteristics or details of allocation concealment.

The primary endpoint’s definition and 1-year timeframe are given, and the summary says participants were followed for two IVF cycles. The registry record does not explain how those descriptions fit together for the primary analysis or how outcomes across cycles were handled. It does not report detailed methods of endpoint ascertainment.

The record does not report the original sample-size justification, a complete statistical analysis plan, the exact test used for the posted p-value, covariate-adjustment details, multiplicity handling, or an analysis-population definition. It identifies a secondary outcome but does not report its results. Adverse-event entries list zero events in the reported categories, but detailed collection and ascertainment procedures are not given; deaths are not reported. These are limits of the registry reporting and should not be converted into assumptions about what did or did not occur during study conduct.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: The Impact of Distress on the IVF Outcome — NCT01103973.
• Registry record last updated 2018-01-18; status last verified 2017-12.
• Results first posted 2016-10-24.
• 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.

21. Record Summary

The registry record describes a completed randomized study of a ten-week mind/body program before a first IVF cycle, compared with a control arrangement involving spa gift certificates. It reports enrollment of 143 and identifies clinical pregnancy rate as the primary outcome, defined by normal fetal heart rate and fetal size at 7 weeks gestation, with a timeframe of 1 year.

The posted outcome percentages are 20.0% for control and 52.0% for the mind/body program. The registry reports an unadjusted p-value of <0.001 and provides comparison estimates with confidence intervals. It also lists a secondary outcome based on psychological status assessed by the Beck Depression Inventory, but does not post its results in the record described.

Important details—including the relationship between enrollment and outcome denominators, missing-data handling, analysis population, multiplicity approach, and original sample-size assumptions—are not reported in the registry record. The record’s single-group model label is not explained alongside its randomized two-group description.