Accurate assessment of PROM is essential because the outcome of pregnancy can be adversely affected by a positive diagnosis.
A speculum examination is helpful in determining the extent of vaginal pooling.
Nitrazine paper on the perineum assesses pH of the fluid.
A blue color indicates alkaline pH. Although alkaline amniotic fluid will be Nitrazine positive, so can urine, which is often alkaline in pregnancy.
Sonographic evidence of oligohydramnios is often present with PROM; however, it has a low specificity and sensitivity for ruptured membranes.
Digital examination should never be done until membrane rupture is ruled out, because of the potential increase in infectious morbidity from ascending vaginal flora into the uterus, leading to chorioamnionitis.