Narrative review examines perinatal microbiota influences and evidence gaps in dogs and cats.

Early-life microbial colonization is increasingly recognized as a key determinant of host development and health. While the perinatal microbiota has been extensively studied in humans, comparable knowledge in dogs and cats remains limited. The present review synthesizes current evidence on the perinatal microbiota in dogs and cats, placing it in the context of advances from human microbiome research while emphasizing biological and management factors relevant to veterinary medicine. The prenatal period represents a window of exposure to the maternal microbiota, which is a key contributor to fetal development, while the occurrence of viable microbial colonization of the fetus in healthy pregnancies is not supported by evidence neither in humans nor in companion animals. After reviewing the features of the maternal gut and vaginal microbiota, particular attention is given to the birth process as a major ecological transition, with delivery mode and birth environment shaping early microbial exposure in species-specific ways. The postnatal period is characterized by rapid microbial succession driven by physiological maturation, early nutrition, and environmental factors. We examine the role of colostrum and milk in shaping neonatal gut microbiota assembly, integrating evidence from human studies with emerging data in dogs. We also discuss how maternal care and other environmental exposures contribute to early microbiota development. Finally, we evaluate microbiota-oriented interventions in veterinary settings, including maternal probiotic supplementation, and discuss their potential benefits and limitations based on available evidence. Throughout the review, we discuss current clinical approaches to the perinatal microbiota in companion animals and identify major research gaps. We conclude by emphasizing the need for well-designed longitudinal and ideally multicentric studies integrating maternal, neonatal, and environmental microbiota data and aimed at developing evidence-based microbiome-informed strategies in veterinary practice.