ObjectiveTo determine if the measurement of hCG levels in vaginal fluid is useful for the diagnosis of premature rupture of membranes (PROM).MethodsAfter irrigating the posterior vaginal fornix with 3 mL. of sterile and procuring vaginal washings, we measured hCG levels. Samples were analyzed from 188 normal pregnant women, 42, 61, and 85 during the first, second, and third trimesters, respectively. Levels of hCG were compared with those of 24 women with confirmed PROM.ResultsThe median and 95% confidence intervals (CIs) of vaginal fluid hCG levels of normal pregnant women were 37.9 (1.9, 725.6), 9.5 (0.8, 95.8), and 6.3 (0.6, 62.2) mIU/mL during the first, second, and third trimesters, respectively. That of women PROM was 420.6 (216.3, 918.3) mIU/mL. For the second trimester, sensitivity was 100%, specificity 91.8%, positive predictive value 82.8%, negative predictive value 100%, and accuracy 94.1%, and for the third trimester, sensitivity was 100%, specificity 96.5%, positive predictive value 88.9%, negative predictive value 100%, and accuracy 97.2%, using a threshold value of 50 mIU/mL.ConclusionThe hCG level in vaginal fluid is a useful marker of PROM during the second and third trimesters.