Maternal-to-neonatal microbial transmission and impact of prenatal probiotics on neonatal gut development

Maternal microbiota during pregnancy plays a crucial role in establishing the neonatal gut microbiota, which is essential for infant health. This study aimed to trace maternal microbial sources contributing to early neonatal gut colonization and assess the effect of prenatal probiotic supplementation on maternal-to-neonatal microbial transmission.

A total of 26 mother-neonate pairs undergoing full-term vaginal delivery were enrolled. From gestational week 32 until delivery, the intervention group received a probiotic supplement containing Bifidobacterium longum, Lactobacillus delbrueckii bulgaricus, and Streptococcus thermophilus twice daily, while the control group received no supplementation. Maternal fecal, vaginal, and placental samples were collected at full term, and neonatal fecal samples were collected longitudinally at Days 1, 3, 14, and 6 months postpartum. Microbial community profiling was performed using 16 S rRNA gene sequencing. Microbial source attribution was conducted using the FEAST algorithm.

Alpha and beta diversity analyses showed that prenatal probiotics transiently altered the composition of neonatal meconium microbiota, with no significant differences observed at later time points. Volatility analysis revealed enhanced microbial stability in the probiotic group during Days 1 to 3 (P < 0.001). FEAST source-tracking indicated that maternal gut and placenta were the major contributors to neonatal meconium colonization, with gut-derived input increasing over time and vaginal contributions remaining minimal throughout. Probiotic supplementation significantly increased the placental contribution to meconium microbiota (P = 0.02), with a sustained but non-significant elevation observed through later stages. Meanwhile, gut-derived and vaginal-derived inputs were consistently reduced in the probiotic group, though these differences did not reach statistical significance.

This study highlights the dynamic nature of maternal-to-neonatal microbial transmission and demonstrates that prenatal probiotic supplementation can transiently reshape early colonization patterns by modulating source contributions.

ClinicalTrials.gov, NCT06241222 ( https://clinicaltrials.gov/study/NCT06241222 ); retrospectively registered on 2024-01-17 (study start 2018-01-01; completion 2021-12-31; first posted 2024-02-05).