The Value of a Single Fetal Fibronectin Assay as a Screen for Preterm Labor and Delivery

Abstract

It has been shown that serial fetal fibronectin sampling has close to a 70% sensitivity in detecting preterm labor or delivery in an asymptomatic population. The objective of this study was to access the usefulness of a single vaginal fetal-fibronectin assay in the mid-second trimester from asympto matic women in predicting preterm labor and delivery. Vaginal samples were obtained from 54 consenting women who received routine prenatal care in our inner-city general obstetrical clinc. A sensitive immunoassay was used for vaginal fetal fibronectin quantitative analysis. Both patients and clinicians were blinded to fetal fibronectin results. Correlation of fetal fibronectin status with outcome was determined. The spontaneous preterm delivery rate was 19% (10/54). The presence of vaginal fetal fibronectin (< 50 ng/ml) had a sensitivity in predicting preterm labor or delivery of 19% with positive and negative predictive values of 38% and 71%, respectively. The specificity was 86% in this study. For women with preterm labor or delivery prior to 34 weeks, fetal fibronectin had a sensitivity of 75%, a specificity of 90% and a negative predictive value of 98%. These results agree with other investigators who have demonstrated that positive fetal fibronectin correlates with preterm labor or delivery within a 3-4 week period of sampling. Although clinicians may find monthly fetal fibronectin sampling impractical, sampling twice in the second trimester (22-24 weeks and 26-28 weeks) may help in identifying those women destined to deliver preterm in the gestational period with the highest neonatal risk and cost (24-32 weeks).

Key Words:

• Fetal fibronectin
• Preterm labor
• Preterm delivery