Purpose: to evaluate the risk of preterm delivery using the fetal fibronectin test and the measurement of the cervix by transvaginal ultrasonography in pregnant women with previous preterm delivery. Methods: one hundred and seven women were enrolled in the study at 24th, 28thand 32ndweek to detect the presence of fetal fibronectin by immediate-reading membrane test and to perform vaginal ultrasonography to measure the length of the cervix between the internal and external cervical os. The cervix was considered to be short when the cervical length was at or below the cutoff set by the receiver-operating characteristic (ROC) curve for prediction of preterm delivery. Sonographic cervical length and fetal fibronectin were compared to assess the risk of preterm birth before 34 and 37 weeks. Results: the spontaneous preterm delivery rate was 37.4% (40/107). The analysis made by the ROC curve indicated 30 mm as the best cutoff to maximize sensitivity and specificity at 24 and 28 weeks and 25 mm at 32 weeks of gestation. The positive test of fetal fibronectin had a significant relative risk (RR: 1.77; 95% confidence interval (IC): 1.10-2.84) to predict delivery before 37 weeks, when compared with a negative test, only at 28 weeks. The presence of short cervix at 24, 28 and 32 weeks showed a significative RR for birth before 37 weeks. The highest RR occurred with a short cervix at 24 weeks (RR: 4.42; 95% CI: 1.25-15.56). Conclusion: we concluded that the measurement of uterine cervix by vaginal ultrasonography is better than the fetal fibronectin test for evaluating the risk of preterm delivery in women with previous preterm delivery.
Fetal fibronectin; Uterine cervix; Preterm labor; Transvaginal ultrasonography
