Natal factors influencing newborn’s oral microbiome diversity: beyond mother-to-newborn microbial transmission

The early microbiota of neonates is crucial for developing the postnatal immune system and establishing normal physiological, metabolic, and neurological functions. This study investigates the pattern of mother-to-newborn microbial transmission and identify factors influencing the diversity of the neonatal oral microbiome. 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. 16S rRNA gene sequencing using oral swab samples 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 transmission of microbes, various natal factors including birth type, birth weight, delivery mode, maternal chorioamnionitis, maternal diabetes and the presence of microbes in other sites influenced the diversity of the neonatal oral microbiome. Among these factors, the birth type was the most significant. The composition of the oral microbiome differed significantly according to the birth type, and preterm neonates exhibited decreased oral microbiome diversity, with fewer beneficial bacteria and more pathogens.