The structure of the human GI microbiota can change during pregnancy, which may influence gestational metabolism; however, a mechanism of action remains unclear. Here we observed that in wildtype (WT) mice the relative abundance of Actinobacteria and Bacteroidetes increased during pregnancy. Along with these changes, short chain fatty acids (SCFAs), which are mainly produced through gut microbiota fermentation, significantly changed in both the cecum and peripheral blood throughout gestation in these mice. SCFAs are recognized by G protein coupled receptors (GPCRs) such as FFA2, and we have previously demonstrated that the Ffar2 expression is higher in pancreatic islets during pregnancy. Using female Ffar2^-/- mice, we explored the physiological relevance of signaling through this GPCR and found that Ffar2-deficient female mice developed fasting hyperglycemia and impaired glucose tolerance in the setting of impaired insulin secretion as compared to WT mice during, but not prior to, pregnancy. Insulin tolerance tests were similar in Ffar2^-/- and WT mice before and during pregnancy. Next, we examined the role of FFA2 in gestational β cell mass, observing that Ffar2^-/- mice had diminished gestational expansion of β cells during pregnancy. Interestingly, mouse genotype had no significant impact on the composition of the gut microbiome, but did affect the observed SCFA profiles, suggesting a functional difference in the microbiota. Together, these results suggest a potential link between increased Ffar2 expression in islets and the alteration of circulating SCFA levels, possibly explaining how changes in the gut microbiome contribute to gestational glucose homeostasis.