MMP9 and atrial fibrillation: Similarly, using Cox proportional hazards regression analyses, high AF levels of lipocalin-2 (hazard ratio: 3.45; 95% CI, 1.99–5.95, P < 0.001), MMP-9 (hazard ratio: 3.47; 95% CI, 1.99–6.02, P < 0.001), and S100 A8/A9 (hazard ratio: 1.78; 95% CI, 1.12–2.84, P = 0.015) were found to be significantly associated with shorter sampling-to-delivery intervals, after adjusting for gestational age at sampling and use of tocolytics.