Why is this important during pregnancy? – Tiny Health

During a vaginal birth, your baby’s microbiome will go through a seeding process as baby passes through the vaginal canal. The vaginal microbiome plays a large role in the seeding process. By optimizing your vaginal and gut microbiome you increase the chances of seeding your baby's gut with beneficial bacteria during birth.

For example, there is evidence that a Lactobacillus dominated vaginal microbiome will actually help to seed beneficial bacteria, like Bifidobacterium from mom’s gut microbiome.