Prolactin concentration in vaginal fluid: a new method for diagnosing ruptured membranes.

Prolactin concentrations were assayed in vaginal fluid, urine and plasma in 20 women between 38 and 41 weeks gestation. Plasma concentrations of 12.3 (7.3-20.8) mU/ml (n = 40) were found whereas urine concentrations were low or undetectable. Vaginal fluid concentrations were generally lower than 0.25 mU/ml but occasionally elevated up to 3 mU/ml in women with unruptured membranes. Half an hour after artificial rupture of the membranes, vaginal fluid prolactin concentrations were always higher than paired maternal plasma concentrations (p less than 0.001). In women suspected of premature rupture of the membranes, prolactin concentrations in vaginal fluid were always higher than the plasma concentrations except in those in whom the clinical outcome showed that the membranes had not ruptured. A rapid prolactin radioimmunoassay is therefore recommended as a new clinical tool for the diagnosis or exclusion of prematurely ruptured membranes.