Preterm birth is a major cause of increased perinatal morbidity and mortality, and the incidence of preterm birth has remained high, at 5-12%, and is on the rise. Conclusions drawn from evidence-based medical studies suggest that fetal fibronectin level detection and cervical length measurement have good clinical value in predicting preterm birth, but there is a lack of relevant studies with large samples in China. How to prevent and predict preterm birth is a hot issue in the field of perinatal birth. The incidence of preterm birth remains high in western developed countries, led by the United States, despite a large number of studies and interventions, and has become a public health problem in developed countries. From 1980 to 2000, the incidence of preterm birth in the United States increased from 9.5% to 11.5%, the incidence of preterm birth in Europe was 6%-10%, and the incidence of preterm birth in China was reported to be 5%-7% in the literature. The main reason why the preterm birth rate in China is lower than that in developed countries is that we set a lower limit of preterm birth at 28 weeks, while in the United States there is no strict lower limit and the general statistics are at 22-24 weeks of gestation. Qu Shouhui’s study reported that the incidence of preterm labor in China was 5.4%, of which therapeutic preterm labor accounted for 1/3, spontaneous contractions 1.2%, and PPROM preterm labor 2.5%, and it is worth paying attention to the fact that preterm labor due to PPROM occupied a high proportion, nearly half of all preterm deliveries. Chunyan Shi et al. studied the predictive value of cervical length in pregnant women with preterm labor and found that cervical length in pregnant women with symptoms of preterm labor was a good predictor of preterm labor. The study of Qu Shouhui investigated the value of cervical length in mid- and late-pregnancy pregnant women for predicting preterm labor using a large sample of more than 5000 cases, and found that. The mean value of cervical length was 38 mm at 22-24 weeks of gestation, 99.4% R30 mm, and the proportions of cervical length <30, <25 and <15 mm were 0.6%, 0.2% and 0.1%, respectively. To et al. reported that cervical length was measured in 6819 pregnant women at 22-24 weeks of gestation and the results showed that 1.6% had a cervical length Q15 mm, the results of Salomon et al. were similar to those of To et al. and the results of the present study were 0.1%. This difference may be related to the difference in ethnicity and lifestyle. The results of the present study showed 34 mm at 28-32 weeks with mild shortening, but >30 mm in more than 90%. 7 % for those <30 and 0.5 % for those <15 mm. Regarding the prediction of preterm birth suggests that the risk of preterm birth is significantly higher in the case of shortened cervical length, the shorter the cervical length the higher the risk of preterm birth, and the risk of preterm birth is 5.5, 11.1 and 13.8 times. The risk of preterm delivery at 28-32 weeks of gestation was 6.9, 11.1 and 20.0 times higher in women with cervical lengths <30, <25 and <15 mm than in women with cervical lengths R30 mm. And the sensitivity of cervical length cervical length in predicting preterm birth increased significantly at 28-32 weeks of gestation. The sensitivity increased from 3% at 22--24 weeks of gestation to 33% at 28--32 weeks of gestation, and the negative predictive value increased to 97%. Overall, the positive predictive value and sensitivity of cervical length shortening was not high, with a high negative predictive value and specificity. The main reason for the low sensitivity is that the causes of preterm labor are multiple. In the study, the risk of PPROM was found to be significantly increased in pregnant women with shortened cervical length at 28-32 weeks of pregnancy, which is 6-8 times higher than that of pregnant women with normal cervical length, suggesting that shortened cervical length at 28-32 weeks of pregnancy is associated with subclinical infection, and pregnant women with shortened cervical length should be checked for The results of Donders et al. The findings of Donders et al. suggest that vaginal inflammation is associated with cervical shortening.Holst et al. also found that cervical length shortening predicted amniotic chorioamnionitis, and the sensitivity of predicting subclinical infection of the reproductive tract in pregnant women with preterm labor <15 mm was 72% and the specificity was 83%.Therefore, attention should be paid to the detection and management of inflammation in those with shortened cervical length in late pregnancy, and also advising the risk of PPROM. CONCLUSION: The routine administration of cervical cerclage, bed rest, and contraction inhibitors for fetal preservation in pregnant women with shortened cervical length (cervical length <25 mm) may prolong gestational weeks and improve pregnancy outcomes.