Abstract: One aspect relates to a composition for predicting preterm birth of the pregnant woman comprising an agent for detecting microorganisms of at least one genus selected from the group consisting of the genus Ureaplasma and the genus Prevotella and microorganisms of the genus Lactobacillus in a vaginal fluid sample of the pregnant woman and a method for predicting preterm birth using the same. According to one aspect, if the relative abundance ratio of the detected microorganisms of at least one genus selected from the group consisting of the genus Ureaplasma and the genus Prevotella is higher than that of normal pregnant woman, and the relative abundance ratio of the detected microorganisms of the genus Lactobacillus is lower than that of normal pregnant woman, it is predicted that preterm birth will occur. Therefore, the composition can be usefully used to predict preterm birth in pregnant women.