The preterm labor index and fetal fibronectin for prediction of preterm delivery with intact membranes.

Objective: To compare the preterm labor index with the biochemical marker fetal fibronectin in predicting preterm delivery.

Methods: In 185 women with preterm labor and intact membranes, the preterm labor index was determined based on clinical findings of uterine contractions, bleeding, and cervical dilatation. An immunosorbent assay was used to measure oncofetal fibronectin.

Results: A significant negative correlation was noted between the preterm labor index and the interval from hospitalization to delivery. Based on a receiver operating characteristic curve, a preterm labor index 4 or higher was defined as positive. Rates of preterm delivery overall and of delivery within 1 week in the preterm labor index-negative group were 55.2% and 13.8%, respectively. Those in the preterm labor index-positive group were significantly higher (88.4% and 56.5%). With respect to predicting when a delivery would occur during the first week of hospitalization, the preterm labor index and fetal fibronectin did not differ in sensitivity (77.7% and 73.8%, respectively), specificity (79.5% and 74.2%), positive predictive value (66.7% and 60.8%), or negative predictive value (84.5% and 83.9%). However, within the preterm labor index-negative group, the rates of preterm delivery (68.4%), delivery within 1 week (28.9%), and neonatal treatment in an intensive care unit (36.8%) were significantly higher in fetal fibronectin-positive than in fibronectin-negative cases (46.2%, 9.0%, and 10.3%, respectively).

Conclusion: The preterm labor index was similar to the fetal fibronectin assay in its ability to predict preterm delivery.