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6: The use of serial cervical length and quantitative fetal fibronectin to identify nulliparous women at risk of subsequent spontaneous preterm birth

      Objective

      To assess whether universal screening using transvaginal cervical length (TVCL) and quantitative fetal fibronectin (fFN) can be used to accurately predict spontaneous preterm live birth (sPTB) in nulliparous women.

      Study Design

      We recruited nulliparous women with singleton pregnancies at 8 clinical sites to identify markers of adverse pregnancy outcomes. Women had a quantitative fFN performed at 3 time points (V1 - 6-14 wks; V2 - 16-22 wks; V3 - 22-30 wks) and TVCL at V2 and V3. Quantitative fFN was run on self-collected swabs and TVCL was measured by certified sonographers. Clinicians were notified if TVCL was < 15 mm (n=301) but fFN results were not reported. Results were evaluated using previously described thresholds thought to be optimal for prediction and over entire ranges of potential thresholds using receiver operating characteristic (ROC) curves for prediction of subsequent sPTB < 37 weeks gestation. Also, the changes in fFN and TVCL between visits, expressed as changes per week (ΔfFN/Δw and ΔCL/Δw, respectively), were evaluated.

      Results

      Of the 9,352 women with at least one TVCL or fFN measurement and necessary pregnancy outcome data, 460 (4.9%) had sPTB. Of the 301 women with TVCL < 15 mm, only 59 received progesterone. Test characteristics for thresholds of quantitative fFN and TVCL are shown in Table 1. TVCL at V2 identified 34/428 (7.9%) and at V3 identified 94/398 (23.6%) of all women with sPTB using the 25 mm threshold. Figure 1 compares the ROC curves for TVCL at V3, fFN at V3, and an initial logistic regression model combining fFN and TVCL at V3.

      Conclusion

      The routine use of self-collected quantitative fFN and TVCL to screen for risk of sPTB is not justified in a nulliparous population. Both tests have limited predictive value individually and from an initial combined model. TVCL at 22-30 weeks was the single best predictor of sPTB, but identified only 23.6% of sPTBs at a threshold of 25 mm. The addition of quantitative fFN to TVCL measurement did not increase the predictive ability of TVCL alone.
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