Nitrazine Swabs are a quick and simple way to test for ruptured amniotic membranes. Individually wrapped swabs with a pH sensitive indicator tip. Color change indicaates the presence of amniotic fluid. With normal vaginal pH level at term somewhere between 4.5-6.0, the tip will turn yellow. When amniotic fluid is present and pH level has risen, the tip will turn blue and show that the pH level is 6.5 or above.