A prospective cohort study was conducted to :1. explore the effective of diet intervention on blood glucose control; 2. observe the changeable composition of microbiota; 3. seek the possible microbiome intervened to prevent GDM.

1. Gestational diabetes mellitus（GDM） is one of the most complications during pregnancy and it is associated with many adverse outcomes for both mother and children in short or long term. Appropriate nutritional intervention is beneficial for the control of blood glucose. However, the strategy of intervention and mechanism remain uncertain. Previous studies have shown that diet maybe influence blood glucose via effecting the composition of gut microbiome. Recently, most studies collect only one sample and combine with the diet review, which have some limitations in revealing the effect of diet on gut microbiota and the process of change in blood glucose. This study aims to achieve the target of controlling blood glucose via diet intervention, which includes staple food distribution, food list and nutritional advice, describe the change of gut microbiota in women with GDM before and after the intervention via amplicon sequencing, estimate the effectiveness of diet intervention on controlling blood glucose and explore the correlation between the level of blood glucose and transition of bacterial diversity by monitoring blood glucose and glycated hemoglobin. Furthermore, explore the mechanism of "diet-bacterial diversity-blood glucose". Investigators hope deeply understand the mechanism of controlling blood glucose via diet intervention and find the effective diet control, probable bacterial intervention, which may be applied in clinical practice.This project is a prospective cohort study designed to explore the effect of diet to control blood glucose on the composition of gut microbiota in women with GDM.
2. The study aims to enroll 50 participants with GDM and 20 participants with non-GDM. They will be provided with medical nutritional intervention and need to collect stool samples before and after intervention, separately. Nutritional professionals provide nutritional suggestions to manage blood glucose via examining food diary . All participants need exam glycated hemoglobin every two weeks and monitor fast blood glucose and 2 hour postprandial blood glucose in a one day. Total times of monitoring blood glucose is at least three times every week. Researchers record the situation of blood glucose both groups. Besides, participants need collect stool sample at 28 weeks (before the intervention) and 32 weeks (after the intervention), respectively. Samples will be sequenced by amplicon to describe the effects of diet intervention on the gut microbiome.

Inclusion Criteria:

• Pregnant women who can have a regular labor inspection and delivery in the labor inspection hospital;
• The range of age is between 18 to 45 years;
• Pregnancy naturally and singleton pregnancy;
• Pregnant women with or without gestational diabetes diagnosed by oral glucose tolerance test at 24 to 28 weeks of pregnancy;
• Those who can skillfully use social software in mobile phones and obey the plan of follow-ups;
• Those who voluntary signing of informing consent.

Exclusion Criteria:

• Patients with pre-pregnancy diabetes or abnormal oral glucose tolerance test screening in early resulting from high risks or known pre-pregnancy glucose intolerance;
• Those who were estimated by endocrinology that their value of blood glucose is controlled by not only diet interventions but also drugs;
• Pregnant women who used antibiotics before 1 month enrollment ;
• Those who combined some metabolic diseases, such as hematological system diseases and nervous system diseases;
• Those who reject signing inform consent.