First trimester interleukin-6 levels help to predict adverse pregnancy outcomes in both thyroid autoantibody positive and negative patients.

AIM: The aim of the present study is to compare pregnancy outcomes among patients with and without thyroid antibodies and/or subclinical hypothyroidism and investigate whether there is an association between first trimester maternal plasma interleukin-6 (IL-6) levels and adverse pregnancy outcomes.

METHODS: A case-control study was carried out including 83 pregnant women (40 thyroid antibody positive and 43 healthy controls). The predictive value of first trimester maternal plasma IL-6 levels on adverse pregnancy outcomes were investigated. The optimal cut-off points of IL-6 for determining maternal and fetal outcomes were evaluated by receiver operating characteristic analyses.

RESULTS: Compared with the control, median IL-6 levels were significantly higher in thyroid antibody positive pregnancies (median 1.58 vs 1.63 pg/mL; P = 0.047). IL-6 levels were found to be significantly higher in women who had suffered a miscarriage (P = 0.002), preterm delivery (P < 0.001), intrauterine growth restriction (P = 0.047), preterm premature rupture of membranes (P = 0.043) and overall prenatal complications (P < 0.001). A statistically significant negative correlation between gestational week at birth and IL-6 levels was also determined among all participants involved in the study (r = -0.385, P < 0.001).

CONCLUSION: IL-6 levels are significantly increased in thyroid antibody positive patients and predictive for future adverse outcomes, irrespective of thyroid autoimmunity. Increased first trimester IL-6 levels independently predict adverse pregnancy outcomes, regardless of subclinical hypothyroidism.