Studying the Prediction of Spontaneous Preterm Birth Using Quantitative Fetal Fibronectin (fFN) for Threatened Preterm Labor: A Pilot Study.

Objective

To determine whether the quantitative value of fetal fibronectin (fFN) can predict preterm birth (PTB) in women with Threatened Preterm Labor.

Design

A retrospective study carried out in WWRC between the years 2017-2022.

Method

A total of 94 patients were selected, all of which had a fFN test and were admitted at 24-33 weeks of gestational age. Concentration of fFN was divided into 5 categories: ≤10, 11-49, 50-199, 200-499 and ≥500ng/mL. A concentration of ≥50ng/mL was classified as a positive test and used as an international cutoff value.

Results

A total of 31 women had a fFN value of ≤10ng/mL; of these, 23 (74.19%) delivered term birth (TB) (≥37 weeks of gestational age), with a mean of 10 and a range of 4-14 delivery weeks following fFN testing (m:10, r:4-14), whilst 8 (25.8%) delivered a preterm birth (< 37 weeks of gestational age) (m:6.37, r:2-12).Following this, 14 women had a fFN value of 11-49ng/mL, of which 12 (85.7%) delivered a TB (m:9.58, r:4-13) and 2 (14.2%) delivered a PTB (m:4, r:1-7). A further 24 women had a fFN value of 50-199ng/mL, of which 9 (37.5%) delivered a TB (m:9.1, r:4-16) whilst 15 (62.5%) delivered a PTB (m:3.88, r:0-7). Of 13 women whose fibronectin value ranged between 200-499ng/mL, 7 (3.84%) had a TB (m:9.42, r:6-13) and 6 (6.25%) had a PTB (m:4.16, r:1-9). Finally, a concentration of ≥500ng/mL was detected in 12 women, of which 2 (16.66%) delivered a TB (m:7.5, r:6-9) whilst 10 (83.33%) delivered a PTB (m:4, r:0-10). The total amount of women with a fFN value of ≥50ng/mL was 49, of which 24 (48.97%) delivered a TB (m:9.5, r:4-16) and 25 (51.02%) delivered a PTB (m:4.28, r:0-11).The remaining 45 women who had a fFN value of ≤50ng/mL resulted in 35 (79.5%) TB (m:8.8, r:4-14) and 10 (20.4%) PTB (m:5.9, r:1-12 weeks). The positive and negative predictive values (PPV and NPV) were found to be 48.97% and 77.77% respectively.

Conclusion

Our preliminary data showed that the quantitative value of fFN alone is insufficient to determine PTB. Other factors should be considered such as cervical length, history of PTB, uterine surgeries, PPROM, and more. It is important to consider the etiology of PTB and apply fFN in cases where the test will benefit. The low PPV and NPV could be attributed to small sample size, therefore a larger study is needed to confirm the findings.