Vitamin D supplementation before in vitro fertilisation in women with polycystic ovary syndrome: multicentre, double blind, placebo controlled, randomised clinical trial.

The introduction cites prior research on vitamin D deficiency prevalence in PCOS, observational links to reproductive outcomes, and conflicting trial evidence. It identifies gaps: small sample sizes, short interventions, single-centre designs, and insufficient follow-up. The rationale that vitamin D supplementation might improve IVF outcomes in PCOS follows logically. Limitations of prior studies are explicitly discussed, including the largest trial's single bolus dose, small samples, and short durations, and the present study addresses these with a multicentre, adequately powered, longer-duration daily-dose design.

Randomisation uses a computer-generated list with variable block sizes (2, 4, 6) stratified by centre, implemented by an independent statistician not involved in recruitment or analysis; the unit is the individual participant. Blinding is maintained through identical capsules and central labelling by two researchers not involved in recruitment; participants, investigators, and analysts are masked. A sample size calculation is reported: 80% power, 5% alpha, assuming 38% vs 48% live birth, targeting 860 participants after 10% loss. Inclusion/exclusion criteria are pre-specified (age 20-42, Rotterdam criteria, specific exclusions for medications, PGT, etc.). The pre-specified analysis plan defines modified ITT, per-protocol, and complete-case analyses, with missing data imputed as negative. Outlier handling is implicitly covered by per-protocol analysis defining poor adherence (<85% intake or <6 weeks). Controls (placebo) are appropriate. No independent replication cohort is reported (not applicable for a single pivotal trial).

Sex is reported (all female). Age, body mass index, PCOS phenotype, duration of infertility, anti-Müllerian hormone levels, and baseline serum 25-OHD levels are all reported in Table 1 with means, SDs, medians, IQRs, and missing data counts. Age and BMI are similar between groups. Demographics include PCOS phenotype breakdown. Because both sexes are not enrolled, sex_justified is not applicable (the study is exclusively in women by design, with a clear disease definition).

The study reports approval from the Ethics Committee of the Women's Hospital of Zhejiang University with a specific protocol number (IRB-20200035-R), followed by approvals from each centre. Informed consent is explicitly mentioned: 'After giving informed consent, participants were randomly assigned.' Regulatory compliance is implicit through the approval by a named IRB and adherence to standard clinical trial regulations; the paper also states it was conducted in accordance with the Declaration of Helsinki by referencing ICMJE and BMJ standards, though the most explicit statement is the ethics committee approval itself. This is a human interventional trial with non-public subject-level data, so all three applicable sub-criteria are adequately reported.

This is a human clinical trial of a drug (vitamin D). The investigational product is adequately identified: manufacturer (Sinopharm Xingsha Pharmaceuticals, Xiamen, China), dose (4000 IU/day as 5 × 800 IU capsules), and identity (calcium-free cholecalciferol). Placebo composition is described (gelatin, glycerin, purified water). The vitamin D assay kit and analyser are identified (Vitamin D 200M Assay Kit, DISIGNS Diagnostics, China; SCIEX Triple Quad 4500MD). Software is identified: Stata 18.0 (StataCorp, USA). Antibodies, cell lines, mycoplasma testing, and organisms are not applicable to this human trial.

The primary analysis uses modified Poisson regression with robust variance (unadjusted) and a random effects model (adjusted for centre). Tests are named. Exact p-values are mostly reported as confidence intervals (the primary result reports RR 1.03, 95% CI 0.91-1.18, and a two-tailed P<0.05 threshold is stated; exact p-values for most comparisons are not given in Table 2 but CIs serve as the primary inferential metric. Assumptions verification is implicit: the use of robust variance and random effects addresses distributional concerns for binary outcomes. Effect sizes (risk ratios, mean differences, risk differences) and 95% CIs are consistently reported. Software is identified (Stata 18.0). Data presentation is appropriate for a large trial: CONSORT flow diagram, baseline table, and per-group n with CIs; individual data points are not required for this sample size. Mathematical plausibility checks: proportions of per-group outcomes in Table 2 (e.g., 52.0% of 435 = 226.2 → 226 is plausible given rounding; 50.2% of 430 = 215.86 → 216 is plausible). Percentages sum appropriately. No arithmetic errors detected.

A data availability statement is present: 'Deidentified individual participant data, and the code for statistical analyses are available at: https://doi.org/10.17605/OSF.IO/F9BC5.' This is a concrete, permanent identifier (DOI) pointing to a repository (OSF), which qualifies as reported_and_adequate for data_availability_statement. The same DOI serves as repository_deposit and satisfies code_sharing. Accession numbers are not applicable (clinical trial data). The paper does not separately mention an additional repository for sequencing or imaging data, so only the OSF link applies.

The trial is prospectively registered (ClinicalTrials.gov NCT04082650). Methods are detailed enough for replication: randomisation, blinding, intervention, IVF procedures, outcome definitions, sample size calculation, and statistical analysis plan are described. A CONSORT flowchart is provided, though the paper does not explicitly mention a reporting checklist submission (e.g., CONSORT checklist); this is a minor omission but common in many published trials. All pre-specified outcomes are reported, including the post-hoc secondary outcome (12-month cumulative live birth) which is transparently labeled as exploratory. Limitations are discussed extensively: higher than expected control event rate, potential selection bias from pandemic, lack of standardised IVF protocol, and the post-hoc outcome. Conclusions are proportional: 'vitamin D supplementation does not improve live birth rates' but 'we could not rule out a modest benefit.' Funding sources (National Key R&D Program of China, NSFC) and competing interests are disclosed in detail.