Abstract: Objective To determine the effect of plasma lipids on gestational diabetes mellitus (GDM) of pregnant women in their first trimester. Methods 354 healthy singleton primiparas were followed up in three hospitals in Chengdu until delivery. Basic information about pregnancy was collected using a questionnaire. Dietary intake was assessed using 24 h dietary recall at (12±1) weeks of gestation. Their total energy intake in the first trimester was calculated with a nutrition calculator. Blood samples of the participants were also taken at the (12±1) weeks of gestation to determine plasma triglyceride (TG), total cholesterol (TC), high-density lipoproteincholesterol (HDL-C), low-density lipoproteincholesterol (LDL-C), fasting blood-glucose (FBG). 75 goral glucose tolerance test (OGTT) was conducted at 24-28 weeks of gestation for the diagnosis of GDM. Multiple logistic regression analyses were performed to estimate odds ratio (OR) of risk factors. Receiver operating characteristic (ROC) curves were drawn to determine the optimal operating point (OOP) of TG level for predicting GDM. Results Women with GDM had significantly higher levels of plasma TG, TC and LDL-C than those without GDM (P<0.05). After adjustment for maternal pre-pregnant BMI and other confounding factors, women with TG≥1.59 mmol/L and 1.26-1.59 mmol/L showed a higher risk of GDM: 3.86-fold 〔95% confidence interval (CI)：1.35-11.08〕 and 2.46-fold (95%CI：1.05-6.51) as compared with those with TG <0.94 mmol/L, respectively. The OOP was determined at 1.27 mmol/L with high sensitivity and specificity, and area under the curve 0.634 (95%CI：0.574-0.711). Conclusion TG level in the first trimester is associated with GDM. It is important to monitor plasma lipids in pregnant women.