# Factors Influencing the Colostrum’s Microbiota: A Systematic Review of the Literature

## TL;DR

This review explores factors affecting the microbiota in human colostrum, highlighting its role in newborn health and the influence of maternal and environmental factors.

## Contribution

The study systematically identifies intrinsic and extrinsic factors influencing colostrum microbiota composition and diversity.

## Key findings

- Colostrum microbiota is predominantly composed of Firmicutes and Proteobacteria, with key genera like Staphylococcus and Lactobacillus.
- Factors such as maternal BMI, delivery mode, and gestational diabetes influence colostrum microbiota diversity and abundance.
- Colostrum may have higher bacterial abundance and diversity compared to mature milk, though results vary across studies.

## Abstract

Background/Objectives: Human colostrum plays a crucial role in early microbial colonization, immune development, and gut health of newborns. Its microbiota is highly dynamic and influenced by numerous factors, yet the determinants remain poorly understood. This systematic review aims to investigate the composition of colostrum microbiota and the intrinsic and extrinsic factors that influence its diversity and abundance. Methods: PubMed and Scopus were systematically searched using a prespecified search phrase. Data on microbial composition, diversity, and influencing factors were extracted and analyzed. The systematic review is registered in PROSPERO (CRD42025644017). Results: A total of 44 eligible studies involving 1982 colostrum samples were identified. Colostrum microbiota consists predominantly of Firmicutes and Proteobacteria, with core genera including Staphylococcus, Streptococcus, Lactobacillus, and Bifidobacterium. Some studies reported higher diversity in colostrum compared to mature milk, while others noted elevated bacterial abundance in the former. Factors influencing colostrum microbiota include maternal BMI, delivery mode, gestational age, diet, gestational diabetes mellitus (GDM), maternal stress, maternal age, secretor status, perinatal antibiotic exposure, neonatal gender, geographic location, feeding type, milk collection method, and mastitis. Conclusions: Colostrum hosts a diverse and dynamic microbiota shaped by multiple maternal, neonatal, and environmental factors. Understanding these influences is crucial for optimizing infant health outcomes, emphasizing the need for further research on the functional roles of colostrum’s microbiota.