IL6 and spontaneous preterm birth: AF IL-6 in the overall population had a very good diagnostic performance with an AUC = 0.82 (95% CI: 0.78–0.85) for HCA prediction, with a sensitivity of 65% (95% CI: 0.55–0.74) and a specificity of 84% (95% CI: 0.76–0.89), performing superiorly for the preterm labor (PTL) group (Area Under Curve (AUC) = 0.88, 95% confidence interval (CI): 0.85–0.91) compared with the Preterm premature rupture of membranes (PPROM) subgroup (AUC = 0.76, 95% CI: 0.72–0.80).