Changes of serum interleukin-6 in healthy pregnant women and establishment of relevant reference intervals

•IL-6 levels are different between non-pregnant and pregnant women.•IL-6 level in the first trimesters is different from the second and third trimesters.•IL-6 levels are no significant difference between the second and third trimester.•Serum IL-6 RIs for the second and third trimester could be combined to calculate.•Serum IL-6 RIs for the first trimester should be established separately. To explore the changes of serum interleukin-6 (IL-6) levels in healthy pregnant women and establish reference intervals (RIs). According to the requirements for the RIs study model and the reference population screening criteria in C28-A3 document, Serum IL-6 levels were measured by electrochemiluminescence immunoassay in 480 healthy Chinese women, including 120 pregnant women in each of the first, second and third trimester and 120 non-pregnant women as the negative control. The establishment of RIs for IL-6 were defined using nonparametric percentile. The RIs for serum IL-6 levels in healthy pregnant women is