Aim To test the hypothesis that altered A Disintegrin and Metalloproteinase Domains with Thrombospondins motifs (ADAMTS) is implicated in the etiopathogenesis of gestational diabetes mellitus (GDM). Methods All pregnant women who underwent elective amniocentesis for karyotype analysis between January 1, 2016, and January 1, 2018, were included in this study. From this cohort, the study group consisting of 20 patients diagnosed with GDM was selected and compared against a control group consisting of 20 age- and body mass index (BMI)-matched patients without GDM. ADAMTS4, ADAMTS5, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) levels were compared in the second trimester amniotic fluid of patients with GDM and normoglycemic pregnant women. Results No significant differences were observed between GDM and control groups regarding age, BMI, gestational age at amniocentesis and indication for amniocentesis. Mean amniotic fluid ADAMTS4 and ADAMTS5 levels were significantly increased in the GDM group compared with the control group (253.5 +/- 18.7 pg/mL and 188.5 +/- 21.3 pg/mL, P < 0.001; 192.9 +/- 16.4 pg/mL and 154.8 +/- 19.9 pg/mL, P = 0.021, respectively). Significant increases in IL-6 and TNF-alpha levels were also detected in the amniotic fluid of GDM patients relative to controls (136.2 +/- 17.3 pg/mL and 98.3 +/- 11.5 pg/mL, P < 0.001; 154.2 +/- 12.5 pg/mL and 86.2 +/- 10.8 pg/mL, P < 0.001, respectively). Conclusion The data presented here suggest that increased levels of ADAMTS4, ADAMTS5, IL-6 and TNF-alpha may play an important role in the progression of GDM. C1 [Melekoglu, Rauf; Yilmaz, Ercan; Bastemur, Ayse G.] Univ Inonu, Fac Med, Dept Obstet & Gynecol, TR-44280 Malatya, Turkey. [Ciftci, Osman] Univ Pamukkale, Fac Med, Dept Med Pharmacol, Denizli, Turkey. [Celik, Ebru] Univ Koc, Dept Obstet & Gynecol, Fac Med, Istanbul, Turkey.