Bacterial invasion of the amniotic cavity is a known cause of adverse pregnancy outcomes, with 12% of all pregnancies ending preterm, resulting in significant morbidity for mothers and babies. Bacterial culture, the gold standard for assessing clinical samples for the presence of infectious agents is slow, resulting in a biased over-representation of the most abundant cultivable microbial species, not necessarily those that cause pathology.
In this study, placentae were collected for gestations reaching at least 37 weeks gestation from women delivering via: (1) non-labouring elective Caesarean section, (2) emergency Caesarean section (3) spontaneous vaginal delivery, and (4) induced and/or assisted vaginal delivery. Placentae were sampled across maternal and fetal sites. DNA extraction was performed using previously published methods and 16S rRNA screening was performed using the 454 pyrosequencing platform.
Preliminary data indicate that the maternal and fetal placental compartments exhibit differential abundance (p < 0.005). Members of the family Enterobacteriaceae and the genus: Staphylococcus, Streptococcus and Lactobacillus demonstrated spatial variability within individual placentae.
The placenta in term deliveries in normal healthy pregnancies is not sterile, irrespective of the mode of delivery and sampling site. Further investigations are required to determine the potential significance of individual microbial community variation in placental tissues, where the fetus encounters long-term exposure to a diverse microbial population long before delivery.
Results from this study have the potential to improve pregnancy outcomes by improving our understanding of how the healthy term fetus is initially colonized by microorganisms, a defining factor in long-term health.