Gestational diabetes mellitus is one of the most common medical comorbidities in pregnancy, including the combination of pregnancy in patients with diabetes mellitus and diabetes mellitus occurring during pregnancy (GDM). A global, multicenter, prospective study by the National Institutes of Health has shown that hyperglycemia is associated with adverse pregnancy outcomes, and that even pregnant women with blood glucose levels in the normal range are at increased risk for cesarean delivery rates, neonatal hypoglycemia, and hyperinsulinemia as their blood glucose levels rise. It is also well documented that the incidence of gestational hypertension, preeclampsia, and antepartum hemorrhage is significantly higher in pregnant women with GDM than in those without GDM. Gestational diabetes mellitus Microproteinuria is more common As early as the 1880s, foreign scholar Viberti introduced the concept of microproteinuria and used it as a sensitive indicator of early renal damage in diabetes mellitus. Some scholars reported that the incidence of microproteinuria in the pregnancy population was 7.8%, while in patients with type 1 diabetes combined with pregnancy, the incidence of microproteinuria and dominant proteinuria were 11% and 5%, respectively, and the incidence of microproteinuria in pregnant women with diabetes combined with pregnancy was significantly higher than that in pregnant women with GDM, which was thought to be related to the damage to renal vascular endothelial cells caused by the persistent hyperglycemic state of pregnant women with diabetes before pregnancy. It is now believed that urinary microprotein creatinine ratio is a sensitive indicator of vascular endothelial function. The occurrence of urinary microprotein may indicate reduced arterial compliance in patients. In addition, patients with metabolic dysfunction are more likely to develop microproteinuria. Even if urinary microprotein excretion is in the normal range, the level of urinary microprotein excretion is significantly associated with renin-angiotensin system activity. Microproteinuria is closely associated with adverse pregnancy Maternal-fetal-placenta as a closely related and interacting whole, and placental vascular endothelial dysfunction from various causes can induce the release of relevant cytokines and hormones in vivo, which have an impact on the vascular endothelial function of the maternal system. There is controversy regarding the occurrence of positive urinary microprotein and adverse pregnancy outcomes. It has been reported in the literature that the incidence of preeclampsia, preterm delivery, premature rupture of membranes, and fetal growth restriction is significantly higher in pregnant women with positive urine microprotein than in those with negative urine microprotein in the second trimester, and especially in early pregnancy, the risk of developing preeclampsia is four times higher in those with positive microprotein than in those with normal microprotein. In addition, urinary microprotein levels are associated with the incidence of preterm delivery. It has been suggested that positive urine microprotein in the second trimester is an independent risk factor for the development of preeclampsia, preterm delivery, premature rupture of membranes, and fetal growth restriction in pregnant women. However, due to the different selection of some study subjects and gestational weeks, some scholars believe that urine microprotein is not a sensitive indicator for predicting preterm birth and preeclampsia, because their findings suggest that urine microprotein excretion is not related to gestational weeks, and urine microprotein creatinine ratio test cannot improve the predictive accuracy of preeclampsia, and that positive urine microprotein is not yet a good predictor of preeclampsia and preterm birth in low-risk pregnant women. Urine microprotein positivity may be the combined result of vascular endothelial dysfunction and metabolic disorders in pregnant patients with gestational diabetes. Many adverse pregnancy outcomes are associated with urine microprotein, and because the incidence of adverse pregnancy outcomes is higher than that of ordinary low-risk pregnant women, urine microprotein may be a not negligible indicator to predict the occurrence of adverse pregnancy outcomes in early stages of high-risk pregnancies such as gestational diabetes mellitus.