Association between interleukin-6 and preterm birth: a meta-analysis

Interleukin (IL)-6 is a pro-inflammatory cytokine that plays an important role in preterm birth (PTB), Several meta-analyses investigated the association between IL-6 and PTB, but definitive conclusion has not yet been achieved. This updated meta-analysis aimed to ascertain the association between IL-6 and PTB by examining IL-6 levels in both normal birth and PTB groups. Prospective cohort studies were retrieved in PubMed, Embase, and the Cochrane library from their inception until 18 February 2020. The primary outcome was the association between IL-6 and PTB, and secondary outcomes were the association between IL-6 and spontaneous PTB. Nine studies involving 1904 patients were included. Overall, IL-6 from different sample types (maternal blood, amniotic fluid and cervicovaginal fluid) was associated with PTB (standard mean difference [SMD]: 0.86, 95% confidence interval [CI]: 0.32 to 1.39, <i>p</i> &lt; 0.001). Furthermore, the association was significant for IL-6 only in amniotic fluid (SMD: 1.87, 95%CI: 0.82 to 2.93, <i>p</i> &lt; 0.001) and cervicovaginal fluid (SMD: 0.46, 95%CI: 0.09 to 0.84, <i>p</i> = 0.022), but not significant in maternal blood (SMD: −0.11, 95%CI: −0.57 to 0.34, <i>p</i> = 0.623). In addition, IL-6 was also associated with spontaneous PTB (SMD: 1.57, 95% CI: 0.18 to 2.95, <i>p</i> &lt; 0.001). Based on the available evidence, IL-6 in amniotic fluid and cervicovaginal fluid might be useful for predicting preterm birth. KEY MESSAGESBased on the available evidenceIL-6 in amniotic fluid and cervicovaginal fluid might be useful for predicting preterm birth Based on the available evidence IL-6 in amniotic fluid and cervicovaginal fluid might be useful for predicting preterm birth