Research question (s)/hypothesis:

1. . The effectiveness of the shared care management of gestational diabetes mellitus;
2. . The cost-effectiveness of the shared care management;
3. . Its sustainability

Method (s) Tianjin three-tier antenatal care network established a universal screening program for gestational diabetes mellitus (GDM) in 1998 and up to 2008, the screening program had screened 115348 pregnant women. GDM will be defined as either fasting plasma glucose (PG) ≥5.1 mmol/L or 1-hour PG≥ 10.0 mmol/L or 2-hour PG≥ 8.5 mmol/L after 75 g glucose tolerance test. A total of 920 pregnant women who have GDM and agree to participate will be randomly assign to have the shared care (diet, physical activity and insulin if indicated) or the local usual antenatal care. The sample size has ≥80% power at a 5% type I error to detect the difference in the primary endpoint, birth weight ≥4000 gram and the secondary endpoint, pregnancy-induced hypertension. Hyperglycemia and other clinical data in the two groups of women will be collected during the shared care or the usual care. Logistic regression and cost-effectiveness analysis will be used in the data analysis.

Public health significance: The introduction of the proven management of GDM in Tianjin antenatal care network will justify the universal screening for GDM and reduce the rate of macrosomic infants and reduce pregnancy-induced hypertension, and thus improve pregnancy outcomes of women with GDM.

Sustainability plan: Just as the universal GDM screening in 1998, the shared care model will be introduced into the Tianjin antenatal care network as part of the usual care routine after the proposed study. The success of the care model will also be publicized and expanded to suburban districts and rural counties of Tianjin, possibly other parts of world where universal screening for GDM is a routine practice.

ACKNOWLEDGEMENT This project is supported by a BRIDGES grant from the International Diabetes Federation. BRIDGES, an International Diabetes Federation project, is supported by an educational grant from Lilly Diabetes."

Inclusion Criteria:

• All pregnant women who are diagnosed to have GDM.

Exclusion Criteria:

• Diagnosis of overt diabetes during OGTT;
• Younger than 18 years of age;
• Non-singleton pregnancy;
• Maternal-foetal ABO blood type incompatibility;
• Maternal diseases such as chronic hypertension,thyrotoxicosis, prepregnancy diabetes and use of long-term medications that may affect glucose metabolism.