Worldwide, preterm birth (PTB) is a significant cause of neonatal mortality and morbidity. Surprisingly, the rate of PTB in the United States is among the top 10 nations in the world, comparable to those of the Democratic Republic of the Congo, Bangladesh, India, and Nigeria. However, there is no predictive biomarker or understanding of the mechanisms of PTB. Recent evidence suggests that the vaginal microbiome can be clustered into Community State Types (CST) and is altered in various obstetrical syndromes. The review aimed to summarize multiple studies on the vaginal microbiome and PTB and identify a particular microbe or CST associated with PTB. We hypothesized that there exists a specific microorganism that, when dominant within the vaginal microbiome, is protective against PTB. We hypothesized that the absence of a particular microbe or CST is a risk factor for PTB. To answer this question, we reviewed the current literature aiming to identify such a microorganism or a group of microorganisms. Our results indicate that no particular microbe or CST can be implicated in PTB. However, the review suggests that an increase in alpha and beta diversity of the vaginal microbiome can be predictive and involved in the pathogenesis of PTB.