Inclusion Criteria:  All of following conditions must be met:  The range of pregnant week is between 8 to 13+6 weeks; The range of age is between 20 to 45 years; Pregnancy naturally and singleton pregnancy; According to the 2020 GDM high-risk population scoring model, those who gets equal to or larger than 80 scores will be assigned to high-risk group and equal to or smaller than 20 scores to low-risk group;  Exclusion Criteria:  Meeting one of the following conditions will be excluded:  Smoking or drinking alcohols; Pregnant women who used antibiotics before 1 month enrollment; Combined with Chronic hepatitis, nephritis, chronic gastritis, gastric ulcer, chronic colitis, hyperthyroidism, hypothyroidism (except subclinical hypothyroidism) and blood diseases before pregnancy; Pregnant women who has a long-term medication history; Those who reject signing the inform consent; Those who has participated other clinical trail in the same period