Adverse pregnancy outcomes in women with type 1 diabetes are associated with multiple alterations in the vaginal microbiome.

AIMS/HYPOTHESIS The vaginal microbiome has been linked to adverse pregnancy outcomes, which are markedly increased in women with type 1 diabetes. To investigate this relationship, we profiled the vaginal microbiome in pregnant women with and without type 1 diabetes, and in relation to pre-term birth (PTB) and pre-eclampsia (PE) in women with type 1 diabetes. METHODS Bacterial and fungal microbiomes were analysed by 16S rRNA gene and internal transcribed spacer 1 sequencing, respectively, in the third trimester of 310 pregnancies (160 with type 1 diabetes) for bacteria, and 147 pregnancies (70 with type 1 diabetes) for fungi. RESULTS The vaginal microbiome was altered by type 1 diabetes in pregnancy, with an increase in the bacterial species Lactobacillus iners and Lactobacillus jensenii, and in the anaerobic genera Gardnerella, Anaerococcus, Prevotella, Dialister, Peptoniphilus and others that are associated with vaginal dysbiosis. In addition, the abundance of the fungal species Malassezia restricta was increased in women with type 1 diabetes. These changes were associated with increased risks of PTB and PE. PTB was associated with higher bacterial alpha diversity, decreased abundance of Lactobacillus reuteri, and increased abundance of Malassezia fungal genus, family Malasseziaceae and order Malasseziales. PE was associated with higher bacterial alpha diversity, increased abundance of Gardnerella vaginalis and decreased abundance of Candida albicans. CONCLUSIONS/INTERPRETATION Adverse pregnancy outcomes in women with type 1 diabetes are reflected by distinct changes in the vaginal microbiome. This highlights the importance of monitoring and managing the vaginal microbiome in high-risk pregnancies, particularly those complicated by type 1 diabetes. Early detection and treatment of risk-associated taxa, e.g. G. vaginalis in the case of PE, could potentially improve vaginal health and pregnancy outcomes in women with type 1 diabetes.