The causes of preterm birth are multifactorial, but its association with infection has been well-
established. The predominant paradigm describes an ascending infection from the lower
genital tract through the cervix and into the presumably sterile fetal membranes and
placenta. Thus, an evaluation of the role of the vaginal microbiome in preterm birth is
implicated. However, emerging fields of data described in this review suggest that the
placenta might not be sterile, even in the absence of clinical infection. We thus propose an …