How to judge amniotic fluid leakage in late pregnancy

So in the late pregnancy can be judged through what ways whether to leak amniotic fluid? First of all, its nourishing state and leucorrhea characteristics he is a lot of difference, it is relatively thin and clear amniotic fluid, then after doing B ultrasound can also be found to reduce amniotic fluid. Then do vaginal examination on the head will find vaginal water symptoms, then in the vaginal secretions detection amniotic fluid is alkaline, you can judge the late when there is no leakage of amniotic fluid symptoms.