Exercise Intervention to Prevent Gestational Diabetes

This study evaluates the role of exercise intervention in reducing the risk of gestational diabetes mellitus(GDM) risk of overweight/obese(prepregnancy BMI≥24kg/m\^2） Chinese pregnant women. Half of participants will have exercise intervention, while the other half will not. Both of the two group will have regular prenatal care.

An increasing number of women are entering pregnancy in an overweight or obese state. The overweight/obesity epidemic among women of reproductive age has led to an increasing incidence of gestational diabetes mellitus (GDM)，and other metabolic and obstetric complications, such as fetal macrosomia, maternal obesity and type 2 diabetes.

Exercise may be a non-invasive therapeutic option for preventing and managing GDM that can be readily applied to the antenatal population.But so far, the effects of exercise interventions on the incidence of GDM and other adverse perinatal outcomes have been scarce, especially in Chinese pregnant women.

So the aim of the investigators study is to evaluate whether exercise intervention in overweight/obese(prepregnancy BMI≥24kg/m\^2） Chinese pregnant women can reduce their risk of GDM and GDM related adverse pregnant outcomes.

Overweight/obese Chinese pregnant women (prepregnancy BMI≥24kg/m\^2） will be randomly divided into exercise intervention group and control group in their first trimester（less than 13 gestational weeks), pregnant women randomised to the exercise intervention group will complete three supervised, exercise sessions each week by using a stational bike, and exercise sessions will be completed on alternate days. Both exercise group and control group have regular prenatal care.

During 24-28 gestatioanl weeks,GDM will be diagnosed by an oral glucose tolerance test (OGTT) according to the new World Health Organization criteria as fasting glucose level in fasting whole blood 5.1 mmol/L or more, or 2-hour value 8.5mmol/L or more.Then the investigators can compare the GDM risk in each group, and find out if exercise intervention can reduce the risk of GDM in overweight/obese Chinese pregnant women.

Following，no matter pregnant women who were diagnosed with GDM in the intervention group or the control group,they will all have standard medical managemen, and continue what they do before until they give birth. That means pregnnat women in the intervention group will continue to have exercise intervention and regular prenatal care despite whether they have GDM or not.

So when they give birth, the investigators can compare pregnant outcomes between four groups, that is exercise group without GDM, exercise group with GDM, control group without GDM and control group with GDM.And the pregnant outcomes include preterm birth rates, fetal birth weight, Aparga score, cesarean rate and so on.

In this study, the investigators will also collect participants' blood samples in first, second and third trimester respectively,and collect cord blood samples, placenta samples,muscle samples and aidpose tissues when they give birh.Thus the investigators can also do some basic reasearch about the potential mechanisms of exercise in preventing GDM.

Eligibility Criteria:
Inclusion Criteria:

* Chinese overweight/obese(prepregnancy BMI≥24kg/m\^2) pregnant women aged between 18 years and 45 years with a singleton live fetus.

Exclusion Criteria:

* High-risk pregnancies or diseases that could interfere with participation (or both), such as heart insufficiency, infectious diseases, cervical incompetence, multiple pregnancy,serious blood diseases, serious hypertension,absence of prenatal control, risk of premature labour.
* Prepregnant type 1 or 2 diabetes mellitus.
* Impaired glucose trolerance (IGT) and impaired fasting glucose(IFG)