Serial salivary estriol to detect an increased risk of preterm birth

Objective: To evaluate serial measurements of salivary estriol (E3) to dete ct increased risk of spontaneous preterm labor and preterm birth. Methods: A masked, prospective, multicenter trial of 956 women with singlet on pregnancies was completed at eight United States medical centers. Saliva was collected weekly, beginning at the 22nd week of gestation until birth, and tested for unconjugated E3 by enzyme-linked immunosorbent assay. Women were separated into high-risk and low-risk groups using the Creasy scoring system. Results: A single, positive (at or above 2.1 ng/mL) salivary E3 test predic ted an increased risk of spontaneous preterm labor and delivery in the tota l population (relative risk [RR] 4.0, P <.005), in the low-risk population (RR 4.0, P less than or equal to .05), and in the high-risk population (RR 3.4, P = .05). Two consecutive positive tests significantly increased the R R in all study groups, with a dramatic improvement in test specificity and positive predictive value but only a modest decrease in sensitivity. In wom en who presented with symptomatic preterm labor, salivary E3 identified 61% of those who delivered within 2 weeks, using a threshold of 1.4 ng/mL. Conclusion: Elevated salivary E3 is associated with increased risk of prete rm birth in asymptomatic women and symptomatic women who present for evalua tion of preterm labor. (Obstet Gynecol 2000;96;490-7. (C) 2000 by The Ameri can College of Obstetricians and Gynecologists.).