This is a randomized controlled trial, aiming to investigate whether a time-restricted eating (TRE) can reduce the incidence of gestational diabetes mellitus (GDM) in high-risk pregnant women. Investigators intend to conduct a 3-month randomized controlled study to compare the effects of 10-hour TRE and habitual eating time on GDM .

Investigators present a multicenter, open-label and parallel-group randomized study. Total 240 women in early pregnancy were randomly assigned to TRE group and SOC (standard of care) group according to the ratio of 1: 1. Participants assigned to the TRE group will be instructed to consume prescribed calories in a 10-hour eating window (from 8:30 am to 18:30 pm) each day and only noncaloric beverages were permitted outside of the eating window over 3 months (from 14-26 gestational weeks). Participants in the SOC group will be instructed to consume prescribed calories following habitual daily eating schedule over 3 months. All participants should follow moderate-intensity physical activity for about 30 minutes every day, and receive diet and exercise counseling during the study period. GDM was diagnosed by 75g oral glucose tolerance test (OGTT) test at about 26 gestational weeks.

Inclusion criteria:

1. Aged 18-50 years;
2. The risk for GDM includes overweight or obesity (BMI ≥ 24 kg/m2 before pregnancy), first-degree relative with diabetes, history of cardiovascular disease, hypertension (≥130/80 mmHg or on therapy for hypertension), HDL cholesterol level < 1 mmol/L and/or a triglyceride level > 2.8 mmol/L, history of GDM, history of macrosomia delivery, individuals with polycystic ovary syndrome, repeated positive fasting urine glucose in the first trimester, or age>45 years according to Guideline of Diagnosis and Treatment of Hyperglycemia in Pregnancy (2022);
3. Less than 14 weeks of gestation;
4. Able to read and complete questionnaires in Chinese;
5. singleton pregnancy.

Exclusion criteria:

1. Pregestational diabetes (including diabetes diagnosed before conception; fasting blood glucose ≥ 7.0 mmol/L or HbA1c ≥ 6.5% in the first trimester; typical symptoms of hyperglycemia or hyperglycemic crisis with optional blood glucose ≥ 11.1 mmol/L);
2. Impaired glucose tolerance (including fasting blood glucose ≥ 5.6 mmol/L or two fasting blood glucose ≥ 5.1 mmol/L in the first trimester);
3. Current or recent use of drugs that affect glucose metabolism such as metformin, glucocorticoids and Orlistat;
4. Severe comorbidities (including cardiac diseases, kidney diseases, hepatopathy, autoimmune diseases, uncontrolled thyroid disease, previous or current malignant tumors, etc.);
5. Fetal malformations or chromosomal abnormalities;
6. Cervical insufficiency (including ultrasonic cervical length < 25 mm before 24 weeks of gestation, history of spontaneous preterm birth at 14-36 weeks of previous pregnancy, or cervical dilation in the past or current pregnancy);
7. Exercise contraindications (including continuous vaginal bleeding, threatened premature labor, placenta previa, premature rupture of membranes, severe anemia, etc.);
8. Drug abuse, which refers to the repetitive, heavy use of drugs with dependent characteristics such as narcotic, psychotropic substances, tobacco and alcohol;
9. Hyperemesis gravidarum, which refers to the severe and persistent nausea and vomiting, unable to eat or eat little that leads to dehydration, ketosis and even acidosis;
10. On a special or prescribed diet for other reasons;
11. Eating window<10 h.

Exit criteria：

1. Failure to comply with or assume the corresponding responsibilities and obligations of the informed agreement;
2. Pregnant women who terminate their pregnancy before completing GDM diagnosis and screening at 24-28 weeks of pregnancy will automatically withdraw from the group, such as severe fetal malformation, eclampsia, abortion, etc.
3. Major diseases, such as particularly serious obstetric medical events, malignant tumors, serious cardiovascular and cerebrovascular diseases, brain injuries, paralysis and other major diseases, can not continue to accept this intervention plan and follow-up, and withdraw from the study;
4. Accidental disability or death caused by non-intervention factors occurred during the study period, and he withdrew from the study;
5. Subjects are subjectively unwilling to continue to accept the intervention program, and sign the withdrawal agreement to withdraw from the group on a voluntary basis, and decide whether to continue to follow up the pregnancy process and outcome according to the specific contents of the withdrawal statement.