MMP9 and preterm premature rupture of the membranes: Kaplan-Meier survival analyses revealed that PPROM women with higher AF levels of lipocalin-2 (≥ 0.36 μg/mL; log-rank test, P < 0.001), MMP-9 (≥ 4.27 ng/mL; log-rank test, P < 0.001), or S100 A8/A9 (≤ 10.99 μg/mL; log-rank test, P = 0.004) exhibited significantly shorter sampling-to-delivery intervals (Fig 4).