Salivary estriol concentrations during normal pregnancies, and a comparison with plasma estriol

Saliva would have advantages over plasma or urine for monitoring estriol during pregnancy. Specimen collection, after stimulation of flow by citric acid, is non-invasive and simple. We measured concentrations of unconjugated estriol in saliva and compared them with those in plasma in normal pregnancies, and found a good correlation (r = 0.79). In addition, trends of concentrations in saliva and plasma were statistically compared and found to be highly correlated. The variation among individuals in the saliva/plasma concentration ratio suggested that some inter-individual factor(s) may affect this relationship. The normal reference interval for unconjugated estriol concentration in saliva from 20 weeks of gestation to term was established.