ABSTRACT Greater than 45% of women in the United States experience excessive gestational weight gain (GWG) leading to increased cardiovascular disease (CVD) risk during pregnancy, postpartum and beyond (≥10 years). Excess fat accumulation and specific fat distribution patterns, such as abdominal visceral fat, accelerate vascular aging in the general population. However, the composition of GWG is scarcely reported. Therefore, a knowledge gap exists in understanding whether the vascular aging response is associated with changes in body composition and fat distribution during pregnancy and postpartum. This proposal supplements the Mother and Infant Determinants of vascular Aging Study (MIDAS; R01HL157075). The MIDAS study will enroll 840 racially and ethnically diverse healthy and medically complicated mother/infant dyads between 34-40 weeks gestation. At 34-40 weeks gestation, within 48 hours of delivery, and at 6 and 12 months postpartum, the MIDAS study will assess vascular aging and CVD risk by measuring pulse wave velocity (PWV), and examine relationships among biologic, personal, social, and ecological disease risk factors with PWV. The objective of this proposal is to elucidate how body composition (Aim 1) and fat distribution (Aim 2) changes during and following pregnancy impact postpartum CVD risk. Although obesity, defined by body mass index, is a proposed modifiable risk factor, body composition (i.e., %fat) and fat distribution (i.e., visceral adipose tissue) were not a focus of the parent grant. Therefore, this proposal will complement the existing MIDAS study by leading the data collection and in-depth analysis of gestational and postpartum body composition. The study specific aims are: 1) determine the association between the trajectory of %fat from 34-40 weeks gestation to 12 months postpartum and PWV at 12 months postpartum in 840 racially and ethnically diverse pregnant women, and 2) determine the association between the change in fat distribution from 6 to 12 months postpartum with PWV at 12 months postpartum in a subset of women (n=280). We will also explore whether race moderates the proposed associations in Aims 1 and 2; racial and ethnic minority women have a greater prevalence of obesity and are at a greater risk for pregnancy complications and CVD compared with non-Hispanic white women. This time sensitive supplement leverages access to a large, diverse cohort of pregnant and postpartum women and a multi-disciplinary team of mentors with expertise in CVD risk and maternal health. As a result, we are well positioned to complete the proposed aims. Additionally, this supplement will enable an early career investigator to: 1) gain experience conducting a well-defined research project evaluating CVD risk in pregnant women, 2) develop her grantsmanship and, 3) expand her research network and learn from a successful mentorship team. This supplement will be an integral component to the MIDAS study by focusing on adiposity- related r...