Obesity is a worldwide pandemic and of women childbearing age in the US, two-thirds are considered overweight/obese. Maternal microbial dysbiosis associated with obesity may play a role in adverse pregnancy outcomes. To better understand the relationship of microbiome and adverse pregnancy outcomes, we utilized the obese hypertensive BPH/5 mouse model of preeclampsia (PE). We hypothesized that the maternal fecal microbiome during pregnancy will differ in the BPH/5 mice compared to lean normotensive C57 controls as well as non-pregnant (NP) BPH/5 females. We have shown that adult BPH/5 female mice have an adverse cardiometabolic phenotype: hypertension and obesity that is exaggerated by pregnancy and phenocopies PE. To test our hypothesis, fecal samples were collected from NP and pregnant (P) BPH/5 and C57 control females in late gestation and Illumina sequencing of 16S v4 rRNA amplicon libraries were used to compare microbiomes. Microbial community composition of BPH/5 compared to C57 P mice were significantly different (variance of 33.59% in PCo1 and Pco2 11.48%, n=9-17, p=0.001, PERMANOVA with Bray-Curtis dissimilarity of 16S Amplicon Sequence Variant’s relative abundance). Alpha diversity was increased in BPH/5 compared to C57 P mice (n=9-17, p=0.005). There was a difference in beta diversity within the communities in BPH5 P mice compared to BPH5 NP mice, suggesting that the fecal microbiome was altered with pregnancy (n=9-17, p=0.006), but no difference was seen in the alpha diversity meaning that the richness and evenness were similar (n=9-17, p=0.115). The most abundant phyla are represented by 49.39% Firmicutes, 38.54% Bacteroidetes, and 7.48% Epsilonbacteraeota. The most abundant genera including 22.59% Alistipes, 19.57% Lachnospiraceae genus unknown, and 9.85% Helicobacter within the BPH5 samples. Muribaculum spp (p=1.58e-06) and Lachnospiraceae_NK4A136_unclassified (p=2.46e-03) showing significant decreases with pregnancy. In conclusion, obese BPH5 dams have altered fecal microbial communities associated with obesity and adverse pregnancy outcomes. Further investigations are necessary to further understand the importance of these microbial community changes and how they play a role in maternal hypertension and offspring.