Abstract: Objective：To investigate the inflammatory factors and coagulation function in patients with gestational diabetes mellitus (GDM) and subclinical hypothyroidism (SCH), and the effects on the pregnancy outcome. Methods：Sixty GDM patients with SCH (the combined group), 55 GDM patients (the simple group) and 60 healthy pregnant women (the control group) were selected. The inflammatory factors, coagulation function and pregnancy outcome in the three groups were compared. Results：Compared with the control group, the level of tumor necrosis factor-α (TNF-α), hypersensitive C-reactive protein (hs-CRP) and fibrinogen (FIB) in the simple group and the combined group were increased significantly (P＜0.05). The above parameters in the combined group were significantly higher than those in the simple group (P＜0.05). There were no significant differences in the levels of activated partial thromboplastin time (APTT) and prothrombin time (PT) among the three groups (P＞0.05). The rate of fetal growth restriction in the simple group and the combined group was significantly higher than that in the control group. The rate of cesarean section in the combined group was significantly higher than that in the control group or the simple group (P＜0.05). There were no significant differences in the incidences of preterm birth and placental abruption in the three groups (P＞0.05). Conclusions：GDM combined with SCH can cause abnormal FIB level, which significantly increases the inflammatory stress and the risk of adverse effects such as fetal growth restriction and cesarean section. Monitoring the inflammatory stress and coagulation function in those patients with GDM and SCH should be strengthened in clinical practice.

Key words: Diabetes, gestational, Hypothyroidism, Tumor necrosis factor-alpha, C-reactive protein, Prothrombin time, Fibrinogen, Pregnancy outcome