Maternal health status is associated with paired maternal and cord blood virome and mother-to-infant transmission.

The viromes of maternal peripheral blood (MPB) and umbilical cord blood (UCB) provide crucial insights into mother-to-infant transmission and the associations of maternal health with early-life viral colonization. Using viral metagenomic sequencing of 433 MPB and 426 UCB samples, we assembled 57 near-complete genomes from four core viral families (Anelloviridae, Circoviridae, Parvoviridae, Flaviviridae). MPB viromes were primarily composed of bacteriophages and Anelloviridae, while UCB exhibited relatively increased abundances of Parvoviridae and Human Endogenous Retroviruses. Maternal disease correlated with reduced α-diversity in MPB but elevated richness in UCB. β-Diversity varied significantly with both health status and sample type. Differential abundance analysis identified health-specific signatures, including enriched Parvoviridae in diseased UCB. Phylogenetic evidence indicated possible vertical transmission and high genetic diversity among identified viruses. This study systematically characterizes the maternal-fetal blood virome and reveals associations between maternal health status and viral community structure, providing a basis for understanding early-life viral exposure and informing future preventive strategies.