A fasting blood glucose of 5.4 mmol/L during pregnancy can be categorized into two types of cases: diabetic combined pregnancy and gestational diabetes, which is usually less serious. 1. Diabetic pregnancy: If diabetes is diagnosed before pregnancy and pregnancy occurs after the diagnosis of diabetes, it is called diabetic pregnancy. In this case, if the blood glucose is controlled during pregnancy and reaches 5.4mmol/L, it means that the blood glucose is well controlled, and this situation is not serious, so there is no need to worry too much. 2. Gestational diabetes mellitus: Different degrees of hyperglycemia caused by abnormalities of glucose tolerance found or occurring during pregnancy, when the abnormalities of blood glucose reach certain diagnostic criteria, it is called gestational diabetes mellitus. In this case, the blood glucose is 5.4mmol/L, but after life interventions the blood glucose can be reduced to normal, the target organs, such as heart, kidney and other functions are also normal, there is no fundus hemorrhage and other complications, then in most cases, the fetus can be normal growth and development, there will be no malformations and other conditions, and is not serious. High blood glucose during pregnancy should be taken seriously, if the blood glucose has been poorly controlled, or even has a tendency to rise, it may cause serious consequences: the pregnant woman may experience various complications, such as ketoacidosis, diabetic microangiopathy, etc.; the fetus may also be affected by high blood glucose, intrauterine growth restriction, or even fetal distress and fetal malformations. During pregnancy, you should pay attention to diet and appropriate exercise, and if high blood sugar occurs, you should seek medical attention in time and follow up according to the doctor’s advice.