Objective:To investigate the expression levels of matrix metalloproteinase-9 (MMP-9), procalcitonin (PCT), soluble triggering receptor expressed on myeloid cells (sTREM-1) and soluble cell differentiation 14 (sCD14) in pregnant women with premature rupture of membranes (PROM) and their predictive value for chorioamnionitis.Methods:A total of 132 pregnant women with PROM who received treatment in Tengzhou Central People's Hospital from January 2016 to June 2017 were included in the study group. These women were assigned to pre-term PROM group (gestational age < 37 weeks, n = 58) and full-term PROM group (gestational age > 37 weeks, n = 74). A total of 106 concurrent full-term healthy pregnant women were included in the control group. Pregnant women in the PROM group were also assigned into an infection group ( n = 51) and a non-infection group ( n = 81). Serum levels of MMP-9, PCT, sTREM-1 and sCD14 were compared between study and control groups, and their value in the diagnosis of PROM complicated with chorioamnionitis was analyzed. Results:The expression levels of MMP-9 [(271.42 ± 34.16) ng/L], PCT [(54.57 ± 8.16) pg/mL], sTREM-1 [(0.51 ± 0.11) ng/mL] and sCD14 [(60.23 ± 9.49) ng/mL] in the study group were significantly higher than those in the control group [(54.97 ± 10.08) ng/L, (26.04 ± 1.98) pg/mL, (0.19 ± 0.04) ng/mL, (42.04 ± 10.33) ng/mL, t = 27.064, 13.767, 14.831, -13.342, all P < 0.01). The expression levels of MMP-9 [(314.05 ± 45.37) ng/L], PCT [(0.61 ± 0.18) ng/mL], sTREM-1 [(63.12 ± 10.12) pg/mL] and sCD14 [(68.07 ± 11.05) ng/mL] in the pre-term PROM group were significantly higher than those in the full-term PROM group [(238.01 ± 40.45) ng/L, (47.87 ± 8.90) pg/mL, (0.43 ± 0.14) ng/mL, (54.09 ± 10.33) ng/mL, t = 9.103, 8.862, -10.538, 6.494, all P < 0.05). The expression levels of MMP-9 [(343.74 ± 43.74) ng/L], PCT [(69.88 ± 8.83) pg/mL], sTREM-1 [(0.67 ± 0.16) ng/mL], sCD14 [(70.41 ± 8.89) ng/mL] in the infection group were significantly higher than those in the non-infection group [(230.09 ± 49.82) ng/L, (45.82 ± 11.04) pg/mL, (0.42 ± 0.19) ng/mL and (54.41 ± 12.42) ng/mL, t = 23.655, 12.014, 9.382, 11.306, all P < 0.01]. The sensitivity (94.23%), specificity (93.75%), positive predictive value (92.45%) and negative predictive value (96.20%) of combined detection of these indexes in the diagnosis of PROM complicated by chorioamnionitis were significantly higher than those of other indexes detected alone (all P < 0.05). Conclusion:Combined detection of serum levels of MMP-9, PCT, sTREM-1 and sCD14 can be used as an effective auxiliary index for the diagnosis of early premature rupture of membranes complicated with chorioamnionitis.