Natal factors influencing newborn's oral microbiome diversity.

The early microbiota of neonates is crucial for developing the postnatal immune system and establishing normal physiological, metabolic, and neurological functions. This study aimed to investigate the factors influencing the diversity of the neonatal oral microbiome, including mother-to-newborn microbial transmission. The study includes a prospective cohort comprising 73 mothers and 87 neonates and a retrospective cohort comprising 991 mothers and 1,121 neonates. Samples from the maternal cervix and neonatal gastric, bronchial, and oral cavities were analyzed using culture-based methods. Neonatal oral swab samples were also analyzed using 16S rRNA gene sequencing to characterize microbial diversity and composition. Similar genera were detected in the neonatal gastric, bronchial, and oral samples, and the neonatal gastric culture was the most similar to the maternal cervical culture. In addition to mother-to-newborn microbial transmission, various natal factors including birth type, birth weight, delivery mode, maternal chorioamnionitis, maternal diabetes and the presence of microbes in other sites influenced neonatal oral microbiome diversity. Among these factors, the birth type was the most significant, and preterm neonates exhibited decreased oral microbiome diversity, with fewer beneficial bacteria and more pathogens. These findings could serve as a baseline for research on the establishment of the oral microbiota in preterm neonates and its health implications.