Introduction Low saliva progesterone concentrations are associated with spontaneous preterm birth (SPTB) in high risk women.1 This study further evaluated the combined use of fetal fibronectin (fFN) and saliva progesterone for SPTB prediction.
Methods A predefined secondary analysis undertaken on a subgroup of women from a prospective cohort (n = 1216) of asymptomatic women at high risk of SPTB. Participants provided at least one saliva sample between 20+0 and 28+6 weeks’ and some underwent a qualitative fFN test (Hologic™; positive test results ≥50 ng/ml). Saliva progesterone concentrations were measured by ELISA (Salimetrics™). Primary end point was SPTB or rupture of membranes with delivery before 34 weeks’. Exclusions: women with iatrogenic PTB before 34 weeks’ and women on progesterone supplementation or in the OPPTIMUM trial.
Results Overall, 638 women with paired saliva progesterone and fFN results (22+0 and 25+6 weeks’) were identified with a SPTB rate <34 weeks’ of 4.5%. A saliva progesterone concentration of <280 ng/l was associated with an odds ratio for delivery <34 weeks’ of 3.81 (95% CI: 1.34 to 10.83); for fFN, the receiver operating characteristic curve (ROC) area for SPTB <34 weeks’ was 0.61 (0.53 to 0.70). Combination of tests improved the ROC area [0.67 (0.56 to 0.78)]. In fFN negative women (n = 583), low saliva progesterone concentrations were associated with greater risk of SPTB <34 weeks’ [positive likelihood ratio 3.4 (1.34 to 8.71)].
Conclusions Saliva progesterone measurement may be useful for prediction of SPTB in high risk women as an adjunct to fFN testing.
Lachelin GCL, et al. BJOG 2009;116:1515–9
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