The role of intestinal microbiota on pre-eclampsia: Systematic review and meta-analysis

•Changes in maternal bacterial proportion can induce complications during pregnancy.•Women with PE show a significant change in alpha diversity in the third semester.•Women with PE had increased relative bacterial abundance compared to controls.•There is an increase in gram-negative bacteria in women with PE. To investigate differences between gut microbiota diversity and composition of healthy pregnant women and women with pre-eclampsia (PE). This is a systematic review and meta-analysis of the literature, in which the terms “pre-eclampsia”, “gastrointestinal microbiome” and “pregnant women” were used to search MEDLINE (PubMed), BVS (LILACS and others), Embase (Elsevier) and Cochrane Library, including observational studies and case-control that investigated changes in the gut microbiota during pregnancy. Six studies were included, with 479 pregnant women. A significantly lower gut microbiota alpha diversity measured as the Shannon index was found in pregnant women with PE in comparison with healthy controls (SMD: −0.47; 95 %IC: −0.77 to −0.18; P = 0.02; I2 = 0 %; three studies, 179 participants), while no significant differences were found in the relative abundance of Bacteroidetes, Firmicutes, Actinobacteria, and Proteobacteria, despite significant differences reported in the individual studies. Pregnant women with PE have lower gut microbiome diversity, however, there is insufficient evidence to determine whether there are changes in gut microbiota composition. The gut microbiota can be a new treatment target to try to prevent changes in maternal bacterial proportions, aiming to reduce complications during pregnancy.