Gestational diabetes mellitus (GDM) is a transient hyperglycaemic condition identified during pregnancy among pregnant women without history of chronic diabetes. Evidence has shown that GDM leads to a series of adverse health outcomes including pre-term birth, progression to pre-diabetes, and type 2 diabetes after delivery in mothers. Interestingly, GDM is getting more and more prevalent in Asian pregnant women, due to the increasing number of overweight and obesity and genetic susceptibility. Even though there is increasing recognition in GDM, the efficiency and efficacy of treating GDM is poor mostly due to its heterogeneity underlined by various pathophysiological mechanisms. Therefore, understanding better on GDM heterogeneity can help clinicians in offering more targeted treatment and follow-up strategy to GDM mothers. This CSAINV proposal aims to define GDM phenotypes in terms of cardio-metabolic profiles in vivo and treatment response during pregnancy, by using a set of unique and novel technology applied (i.e. continuous glucose profiling and untargeted metabolites profiling). In this proposed 3-year pregnancy cohort, we will recruit 800 overweight or obese Asian pregnant women in early pregnancy without a history of diabetes until delivery. We aim to develop a systematic antenatal and postnatal screening, treatment and intervention guidance in GDM mothers.