The predictive values of cervix length (CL) measurement based on transvaginal ultrasonography (TVUS) and pathological examination of placenta for premature delivery (PTD) were investigated, and the correlation between PTD and infection was analyzed. A total of 120 pregnant women with PTD or high-risk factors for PTD admitted to Hengyang Maternal and Child Health Hospital, between February 2020 and March 2022 were included in this retrospective study. There were 36 subjects in the PTD group and 84 in the normal delivery group (control group). They underwent pathological examination of the placenta and TVUS for CL measurement. The final gestational age was set as the standard for the evaluation of the predictive values of pathological examination of the placenta and TVUS. Moreover, a pathological examination of the placenta was used to analyze the correlation between PTD and infection. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of joint inspection were remarkably superior to those of single CL or pathological examination of the placenta (p<0.05). The proportion of pregnant women with CL ≤30 mm and positive placental pathology was higher than that of pregnant women with CL >30 mm and negative placental pathology (p<0.05). In addition, the incidence of Ureaplasma urealyticum (UU), Chlamydia trachomatis (CT), and chorioamnionitis (CA) in the vaginal discharge of the PTD group was markedly superior to that of the control group (p<0.05). The combination of CL ≤30 mm and positive placental pathology could effectively predict PTD, and placental infection was notably correlated with the occurrence of PTD.