Premature rupture of membranes (PROM) is defined as the rupture of membranes before delivery. The diagnosis is important because it is clearly associated with maternal-fetal infection, cord prolapse, and preterm labor. The diagnosis of PROM can be easily made when amniotic fluid is found in the cervical os, but sometimes it is difficult to make the diagnosis when the rupture is small and the clinical signs are not obvious. Nitrozine test paper, microscopic finding of amniotic crystals formed by NaCl, intra-amniotic injection of dye, and detection of biochemical substances in vaginal douche (e.g., AFP, hCG, PRL, fibronectin) are also used to diagnose PROM, but these methods are either more expensive or more time-consuming, and their sensitivity and specificity are low, and some of them are invasive, so more inexpensive and cost-effective methods need to be sought. Urea and creatinine are two common indicators of renal function, which have been widely used in clinical practice and are easy and rapid to detect. Given that fetal urine is the most important source of amniotic fluid in mid to late pregnancy, we envisioned that testing the urea and creatinine values of vaginal douche may be useful in the diagnosis of PROM, and we report it as follows. 1. Subjects and methods (1) Study subjects From August 2006 to October 2007, 56 pregnant women (29-41 weeks of gestation) were admitted to the Obstetrics Department of the First Affiliated Hospital of Soochow University with complaints of vaginal fluid, of which only 40 cases were enrolled. The remaining 13 were admitted because of spontaneous or vaginal bleeding after vaginal speculum examination, or the presence of regular contractions, other pregnancy-related diseases, multiple pregnancies, or the presence of conditions that could affect fetal urine production, or were on medication, or did not meet the findings of the following vaginal examinations. All patients were admitted for vaginal examination under sterilization, and those who saw amniotic fluid flowing from the cervical os after pushing up the fetal previa and forming a posterior vaginal vault fluid, as well as a posterior vault fluid that could turn the nictitating paper blue, were enrolled in the premature rupture of membranes group (PROM group). At the same time, 40 pregnant women without any complaints of discomfort, no pregnancy-related diseases and intact fetal membranes were randomly selected as the control group (Control group) among the pregnant women in the prenatal examination at the same time, and their informed consent was obtained. (2) Methods Collection of vaginal douche fluid. On admission, the posterior vaginal vault was exposed with a vaginal speculum under vulvar and vaginal disinfection, and 5 ml of sterilized saline was injected into the posterior vaginal vault with a syringe, and 3 ml was aspirated with the same syringe, which was immediately sent to the laboratory for the detection of urea and creatinine by dry chemistry using a Johnson & Johnson Vistros 250 automatic biochemistry meter and corresponding supporting reagents. 2. Statistical processing. With the help of SPSS 10.0, the comparison of measurement data between two groups was performed by independent samples t-test. The area under a R0C curve (AUC) was analyzed by applying the receiver operating characteristic (ROC) curve to determine the optimal cutoff values of urea and creatinine.