We hypothesized that elevated vaginal levels of matrix metalloproteinase-8 (MMP-8), interleukin-8 (IL-8) and the 70kDa heat shock protein (hsp70), compounds involved in inflammatory responses, correlated with a short cervix in pregnant women.This prospective cohort study used a convenience sample of 64 women in their early third trimester with a singleton pregnancy. A short cervical length was present in 35 women (54.7 %). Vaginal fluid was tested for levels of MMP-8, IL-8 and hsp70 by enzyme-linked immunosorbent assay (ELISA). A receiver operating charasteristic (ROC) analysis was used to calculate the area under the curve (AUC) for each mediator in predicting short cervical length.MMP-8 (109 vs 29.6 ng/ml, p=0.014), IL-8 (689 vs 330 pg/ml, p=0.007) and hsp70 (4.4 vs 2.9 ng/ml, p=0.036) were all elevated in vaginal samples from women with a short cervix. In addition, there was a negative association between the concentration of each compound in vaginal fluid and cervical length p≤0.026). The vaginal IL-8 concentration had the highest negative correlation with a short cervix (AUC=0.7, p=0.007).MMP-8, hsp70 and IL-8 contribute to a pro-inflammatory cervico-vaginal milieu that weakens cervical integrity and leads to a shortening in cervical length (Tab. 4, Fig. 1, Ref. 27).