Umbilical Cord Blood Biomarkers for Early Risk Stratification of Childhood Asthma and Atopic Dermatitis: A Developmental and Critical Appraisal.

Asthma and atopic dermatitis (AD) often begin along developmental trajectories established before birth, making umbilical cord blood an attractive source of biomarkers for early risk stratification. However, association with later disease is not equivalent to clinically useful prediction. This critical narrative review evaluates five linked layers-baseline susceptibility, prenatal exposure windows, placental and cord blood mediator signals, postnatal modifiers, and phenotype-specific outcomes-through a clinical-prediction lens. Cord blood is uniquely positioned at birth and supports cellular, serologic, epigenetic, transcriptomic, and metabolic assessment before most postnatal infections and treatments. Its limitations include single-time-point sampling, maternal-blood contamination, uncertain analyte origin, delivery-related perturbation, cellular-composition effects, and matrix heterogeneity. Most studies of IgE, cytokines, chemokines, immune-cell markers, methylation, microRNA, and metabolic or exposure-related analytes report associations rather than validated prediction models; few test incremental value beyond a prespecified clinical model, calibration, clinical net benefit, or external validation. Current evidence therefore supports cord blood primarily as a mechanistic and risk-context biospecimen; no marker or panel is ready for routine screening. We provide a disease-specific, actionable go/no-go roadmap that moves candidates from a locked cord blood panel through incremental-value testing, external validation, feasibility assessment, and intervention-linked impact studies.