Prediction of Preterm Birth by Using Qualitative Fetal Fibronectin Test Combined with C-reactive Protein

Park, Jeong Kuy; Park, Sun Hui; Her, Yun Su; Yang, Mi Ai; Lim, Hyun; Jeong, Young Ju; Cho, Sung Nam; Kim, Jong Duk

Abstract

OBJECTIVE
The qualitative test of fibronectin of the cervices and vaginae as well as the C-reactive protein test of pregnant mothers with symptoms of preterm labor were performed in an attempt to examine clinical validity of these factors as predictable elements of preterm delivery.
METHODS
This prospective study was conducted on ninety (90) single pregnancies of gestational age from 24 weeks and 1 day to 34 weeks and 6 days admitted to the hospital with symptoms of preterm labor, which occurred in the period from October 1, 1999 through March 31, 2001. Among these pregnant women, those with a uterine contraction rate of 4 per hour or greater and uterine dilatation of less than 3 cm without PROM were used as the subjects. The qualitative test of fetal fibronectin (ROM check, Adeza Biochemical, USA) of the cervices and vaginae as well as the C-reactive protein test by means of latex agglutination method using maternal blood were performed on these subjects. Of the 90 mothers that participated in this study, 15 dropped out and 75 underwent the qualitative test of fetal fibronectin and C-reactive protein test. The results of each test and the combined tests of both at preterm delivery (1) within 1 week, (2) prior to 34 weeks and (3) prior to 37 weeks were compared and analyzed.
RESULTS
1. 22.4% (15/67) resulted in preterm delivery prior to 34 weeks while 48.0% (36/75) ended up with preterm delivery prior to 37 weeks. 2. In predicting preterm delivery within 7 days and prior to 37 weeks after the test, the fetal fibronectin and C-reactive protein qualitative test were statistically insignificant. The combined tests of both fetal fibronectin and C-reactive protein were statistically insignificant in predicting preterm delivery within 7 days (Odds ratio of 4.2; 95% CI 0.7-23.3 p=0.199) and prior to 37 weeks (Odds ratio of 5.3; 95% CI 0.6-48.3 p=0.116). 3. In predicting preterm delivery prior to 34 weeks, fetal fibronectin and C-reactive protein qualitative test were insignificant statistically. Nevertheless, these two tests in combination showed a statistical significance for preterm delivery prior to 34 weeks: It showed a sensitivity of 26.7% (4/15), a specificity of 95.6% (43/45), a positive predictability of 66.7% (4/6), and negative predictability of 79.6% (43/53) [Odds ratio of 7.8; 95% CI 1.3-48.3, p=0.03].
CONCLUSION
Specificity and positive predictive value improved when the combined fetal fibronectin and C-reactive protein tests in pregnancies with symptoms of preterm labor were performed for preterm delivery before 34 weeks. Consequently, this is a clinically valid predictor of preterm delivery before the 34th week.