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

Background: 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.Material and methods: 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.Results: 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, p < 0.001). Furthermore, the association was significant for IL-6 only in amniotic fluid (SMD: 1.87, 95%CI: 0.82 to 2.93, p < 0.001) and cervicovaginal fluid (SMD: 0.46, 95%CI: 0.09 to 0.84, p = 0.022), but not significant in maternal blood (SMD: -0.11, 95%CI: -0.57 to 0.34, p = 0.623). In addition, IL-6 was also associated with spontaneous PTB (SMD: 1.57, 95% CI: 0.18 to 2.95, p < 0.001).Conclusions: Based on the available evidence, IL-6 in amniotic fluid and cervicovaginal fluid might be useful for predicting preterm birth.