Purpose of Investigation: To determine the accuracy from three diagnostic methods for premature rupture of membranes. Materials and Methods: Samples from 100 pregnant women were divided into two groups: intact and ruptured membranes. Samples of 2-5 ml were collected from the vaginal content and the exams were performed, analysing accuracy measures. Results: The pH demonstrated sensitivity of 100.0%, specificity of 96.0%, positive predictive value (PPV) of 96.2%, negative predictive value (NPV) of 100.0%, and accuracy of 96.0%. Iannetta test demonstrated sensitivity of 86.0%, specificity of 92.0%, PPV of 91.5%, NPV of 86.8%, and accuracy of 79.1%. Crystallization demonstrated sensitivity of 90.0%, specificity of 98.0%, PPV of 10.00%, NPV of 90.7% and accuracy of 88.2%. Conclusion: The most specific test with higher PPV was crystallisation, alone or in combination with others (pH and Iannetta test). The most sensitive test with higher NPV and accuracy was pH, alone or in association with others (Iannetta test and crystallization).