Extracellular matrix‐related and serine protease proteins in the amniotic fluid of women with early preterm labor: Association with spontaneous preterm birth, intra‐amniotic inflammation, and microbial invasion of the amniotic cavity

Abstract Problem We aimed to determine whether altered levels of various extracellular matrix (ECM)‐related and serine protease proteins in the amniotic fluid (AF) are associated with imminent spontaneous preterm birth (SPTB; ≤7 days) and intra‐amniotic inflammation and/or microbial invasion of the amniotic cavity (IAI/MIAC) in women with early preterm labor (PTL). Method of study This retrospective cohort study included 252 women with singleton pregnancies undergoing transabdominal amniocentesis who demonstrated PTL (24–31 weeks). The AF was cultured for microorganism detection to characterize MIAC. IL‐6 concentrations were determined in the AF samples to identify IAI (≥2.6 ng/mL). The following mediators were measured in the AF samples using ELISA: kallistatin, lumican, MMP‐2, SPARC, TGFBI, and uPA. Results Kallistatin, MMP‐2, TGFBI, and uPA levels were significantly higher and SPARC and lumican levels were significantly lower in the AF of women who spontaneously delivered within 7 days than in the AF of those who delivered after 7 days; the levels of the first five mediators were independent of baseline clinical variables. In the multivariate analysis, elevated levels of kallistatin, MMP‐2, TGFBI, and uPA and low levels of lumican and SPARC in the AF were significantly associated with IAI/MIAC and MIAC, even after adjusting for the gestational age at sampling. The areas under the curves of the aforementioned biomarkers ranged from 0.58 to 0.87 for the diagnoses of each of the corresponding endpoints. Conclusion ECM‐related (SPARC, TGFBI, lumican, and MMP‐2) and serine protease (kallistatin and uPA) proteins in the AF are involved in preterm parturition and regulation of intra‐amniotic inflammatory/infectious responses in PTL.