ABSTRACTA balanced vaginal microbiome dominated byLactobacilluscan help promote women’s reproductive health, withLactobacillus crispatusshowing the most beneficial effect. However, the potential role of vaginal microbiomes in hypertensive disorders of pregnancy (HDP) development is not thoroughly explored. In this nested case-control study based on an assisted reproductive technology follow-up cohort, we prospectively assessed the association between pregestational vaginal microbiomes with HDP by collecting vaginal swabs from 75 HDP cases (HDP group) and 150 controls (NP group) and using 16S amplicon sequencing for bacterial identification. The vaginal microbial composition of the HDP group significantly differed from that of the NP group. The abundance ofL. crispatuswas significantly lower, and the abundances ofGardnerella vaginaliswas significantly higher, in the HDP group than in the NP group. Of note,L. crispatus-dominated vaginal community state type was associated with a decreased risk for HDP (odds ratio = 0.436; 95% confidence interval, 0.229 to 0.831) compared with others. Additionally, network analysis revealed different bacterial interactions with 61 and 57 exclusive edges in the NP and HDP groups, respectively. Compared with the HDP group, the NP group showed a higher weighted degree and closeness centrality. Several taxa, includingG. vaginalis,L. iners, and bacterial vaginosis-associated bacteria (Prevotella,Megasphaera,Finegoldia, andPorphyromonas), were identified as “drivers” for network rewiring. Notable alterations of predicted pathways involved in amino acid, cofactor, and vitamin metabolism; membrane transport; and bacterial toxins were observed in the HDP group.IMPORTANCEThe etiology of HDP remains unclear to date. Effective methods for the individualized prediction and prevention are lacking. Pregestational vaginal dysbiosis precedes the diagnosis of HDP, providing a novel perspective on the etiology of HDP. Early pregnancy is the critical period of placental development, and abnormal placentation initiates HDP development. Thus, disease prevention should be considered before pregnancy. Vaginal microbiome characterization and probiotic interventions before pregnancy are preferred because of their safety and potential for early prevention. This study is the first to prospectively assess associations between pregestational vaginal microbiome and HDP.L. crispatus-dominated vaginal community state type is linked to a reduced risk for HDP. These findings suggest that vaginal microbiome characterization may help identify individuals at high risk for HDP and offer potential targets for the development of novel pregestational intervention methods.