BACKGROUND: Gestational diabetes mellitus (GDM) has a strong relationship with an increased risk of maternal and perinatal complications. However, in Basrah, Iraq, studies regarding GDM are still limited. In current study, we aimed to investigate the association between insulin resistance and some clinical predictors of GDM among pregnant women in 1st and 3rd trimesters of gestation.METHODS: This case-control study was conducted on 44 pregnant women with GDM and 45 without GDM aged 20 to 40 years who applied for GDM screening during the first (9-13 week) and third trimester (24-28 week) of pregnancy. Demographics, blood glucose, HbA1c, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), spexin, nesfatin-1, orexin-A, vaspin and lipid profile levels were compared between groups.RESULTS: Subjects with GDM showed a higher level of glucose, insulin HOMA-IR, HbA1c, spexin, vaspin in the first and third trimesters of pregnancy (p<0.01) compared to the healthy subjects. Meanwhile in the first and third trimester, subjects with GDM showed significantly lower level of nesfatin-1 and orexin-A compare to the control. In third trimester, oral glucose tolerance test (OGTT) outcomes for fasting glucose at 1 hour, 2 hours, and 3 hours after glucose load were significantly higher (p<0.01). According to the area under the receiver operating characteristics (ROC) curve (AUC) findings, HOMA-IR, spexin, and vaspin may be more effective predictors biomarkers for GDM in pregnant subjects, while orexin-A and nesfatin-1 were ineffective.CONCLUSION: The correlation of insulin resistance and adipokines in the first and thrid trimester was not significantly different, which may cast new light on the possible role as an etiological cause of GDM and might be a better monitoring parameter in women with GDM. KEYWORDS: gestational diabetes mellitus, insulin resistance, vaspin, spexin, orexin-A, nesfatin-1