Prepregnancy body mass index (BMI) and gestational weight gain (GWG) have Significant effects on the risk of pregnancy outcomes such as gestational hypertension disease and gestational diabetes mellitus in singleton pregnancies. This paper is to investigate the relationship between pre-pregnancy body mass index (BMI) and weight gain during pregnancy and pregnancy outcomes in women with twin pregnancy.

Inclusion Criteria:

• Age 18 ~ 41 years old;
• The gestational age of the first diagnosed twin pregnancy is ≤10weeks;
• Double chorionic double amniotic sac pregnancy;

Exclusion Criteria:

• with heart disease, liver disease, kidney disease, complications (chronic hypertension, hyperthyroidism, diabetes and others ), genetic diseases, psychological and mental diseases;
• with history of habitual abortion and cervical insufficiency;

Eligible participants is female.

The participants include women with twin pregnancy meeting the inclusion criteria