Project abstract The research proposed in this supplement study expands on the parent study, which aims to determine interrelationships among abdominal fat accretion, sedentary behavior during pregnancy, and maternal cardiorespiratory fitness (CRF), and the independent and interactive effects on GDM risk, defined as insulin sensitivity and β-cell function. Our proposed study will characterize current physical activity patterns using accelerometer data collected in a racially-diverse group of 115 pregnant women from the parent study at each trimester (Aim 1), and will further determine associations between free-living moderate and vigorous activity levels and our two primary metabolic outcomes, insulin sensitivity (Aim 2A) and β-cell function (Aim 2B) at 26- 28 weeks gestation. If funded, this supplement award will also provide support for five student trainees to help conduct this research and participate on our supportive and engaging team environment at Kennesaw State University, a large, undergraduate-focused R2 university.