The main reasons for not being able to do glucose test in early pregnancy include fetal instability, easy misdiagnosis, and not reaching the peak of incidence. 1. Fetal instability: nausea, vomiting and other pregnancy symptoms are obvious in early pregnancy, and it is necessary to take a lot of glucose water before doing glucose tolerance, which is easy to aggravate the pregnancy reaction of pregnant women. 2. Easily misdiagnosed: estrogen and progesterone in early pregnancy will affect insulin secretion and interfere with the results of glucose tolerance test, making it easy to misdiagnose. 3. Not to the peak of the onset of the disease: early pregnancy is not particularly obvious changes in the demand for blood glucose, the probability of gestational diabetes in early pregnancy is relatively low, the demand for blood glucose after 24 weeks of pregnancy is obvious, and then do glucose tolerance, which seems to be more necessary. Glucose tolerance is usually done in the 24-28 weeks of pregnancy, but the symptoms of high blood sugar in early pregnancy, you can also go to the hospital in time to do glucose tolerance.