Table 2.

Major bacterial taxa found during pregnancy and its complications, at each colonization site, according to the studies discussed in the review.

	Pregnancy
Gut	-especially in the third trimester, reduction in maternal gut microbiota diversity, with the increase of Proteobacteria [75,86], Streptococci, Lactobacilli [75] Bifidobacteria and species producing lactic acid [86] -in overweight women, reduction in Bifidobacterium spp. and Bacteroides, and increase in Enterobacteriaceae, Staphylococcus spp., Escherichia coli [84,87] -higher percentage of pathogenic bacteria, such as Clostridium perfringens and Bulleidia moorei, and a reduction in the Coprococcus catus in mothers affected by preeclampsia, while healthy controls were mostly characterized by Bacteroidetes spp. [88]
Oral cavity	-during the third trimester, increase in bacterial diversity and total amount [75,89,90]
Vagina	-progressive reduction in anaerobic bacteria and increase in Lactobacillus spp. [91,92]
Placenta	-prevalence of E. coli [5] -similarities with the oral microbiota [5] -Lactobacilli, Propionibacteria, Enterobacteriaceae [30] -in women who undergoing elective Cesarean section, lower diversity index and prevalence of Proteobacteria [93] -higher percentage of Acinetobacter spp. in women with gestational diabetes mellitus [94]