ObjectiveTo investigate the expression of amniotic fluid levels and blood serum levels of matrix metalloproteinases-8 (MMP-8) and interleukin-6 (IL-6) in women with preterm delivery. MethodsBetween January 2010 and December 2012, we collected the amniotic fluid of 102 preterm pregnant women and 98 full term pregnant women and analyzed the MMP-8 levels and IL-6 levels in amniotic fluid and blood serum. Meanwhile, we also collected the amniotic fluid to do bacterial culture. ResultsThe amniotic fluid levels of MMP-8 in preterm pregnant women were higher than those in full term pregnant women [(320.45±59.88) vs (153.72±29.12) ng/mL, P<0.05], but there was no obvious discrepancy in the blood serum levels of MMP-8 in the two groups [(9.56±2.11) vs (9.42±2.01) ng/mL, P>0.05]. Both amniotic fluid levels and blood serum levels of IL-6 in preterm pregnant women were significantly higher than the full term pregnant women [(90.5±16.3] vs (20.6±12.5) μg/L, P<0.05; (159.2±20.4) vs (22.3±11.8) μg/L, P<0.05]. The positive bacterial culture rate of preterm pregnant women was higher than the full term pregnant women (8.8% vs 1.0%, P<0.05). ConclusionInfection is the most important reason for preterm pregnancy. MMP-8 level increases in the amniotic fluid, and the level of IL-6 in amniotic fluid and blood serum is a valuable clinical index for identifying premature delivery.