Premature rupture of membranes refers to the rupture of the membranes before labor, with amniotic fluid leaking intermittently. For the diagnosis of premature rupture of membranes, the following methods are primarily used. First, through the symptoms of the patient, when the membranes rupture prematurely, a clear liquid intermittently leaks from the vagina. However, this liquid must be distinguished from vaginal secretions and urine. Second, judgement can be made based on the presence of fern-like crystals in the amniotic fluid. A small amount of the liquid can be taken and observed under a microscope, and if distinct fern-like crystals are observed, it can be concluded that there is premature rupture of membranes. Third, the use of premature rupture of membranes test strips can aid in diagnosis. If the test strip changes color upon contact with the leaking fluid, it can be definitively diagnosed as premature rupture of membranes. Fourth, ultrasound can serve as a supplementary method, as amniotic fluid often decreases with premature rupture of membranes, and an ultrasound can reveal amniotic fluid levels below the normal range.