Project Summary/Abstract Weight gain patterns during the first year of life are a critical risk factor for long-term cardiometabolic health from infancy through adulthood. Infant obesity risk is influenced by appetitive traits in the first 3 months. These appetitive traits, food responsiveness (FR) and satiety responsiveness (SR), reflect food approach and avoidance behaviors, respectively. However, little is known about factors that affect FR and SR development during infancy, which may inform novel, effective behavioral interventions for obesity risk. Emerging data indicate that sleep and circadian rhythms are related to appetite in children and adults, although little is known about how sleep and circadian rhythms are associated with appetite development in infants. We posit the novel hypothesis that infant sleep/circadian rhythm patterns affect infants’ appetite, and together, they impact infants’ obesity risk. We also posit that the degree of synchronization between maternal and infant circadian rhythms further affects infant appetite development and obesity risk. In the proposed study, pregnant individuals (N=230, body mass index ≥18.5 kg/m2) will be recruited in their third trimester. We acknowledge that not all who give birth identify as women or females. We use the terms "pregnant women," "postpartum women," “maternal,” and "mothers" to refer to all birthing people throughout this application. Maternal-infant sleep and circadian rhythms (focused on rest-activity rhythms and nighttime feeding), along with infant appetite and weight, will be assessed via objective and subjective methods at 1-, 3-, 6-, and 12-months after birth. Thus, to identify potentially modifiable influences on infant weight trajectory, the specific aims are to: (1) determine the concurrent and predictive effects of infant sleep/circadian rhythms on infant appetite development in the first 6 months of life; (2) identify the combined effects of early infant appetite and disrupted sleep/circadian rhythms on rapid infant weight gain in the first 6 months and infant weight outcomes at 12-months; and (3) explore the role of maternal-infant synchronization of rest-activity rhythms in the models of infant sleep/circadian rhythms and appetite predicting infant weight. This proposal addresses compelling questions about sleep, circadian rhythms, and obesity identified in the NHLBI Strategic Vision and NIH Strategic Plan. Notably, in alignment with the Katz Early Stage Investigator Research Grant Program, this proposal involves innovative changes in the PI’s research direction: (1) new population (moving from mothers to infants); (2) new methods (moving from self-report to objective assessment and dyadic metrics); and (3) new potential therapeutic targets (moving from eating-related targets to sleep/circadian rhythms & maternal-infant synchronization). The PI and investigative team have the content and methodological expertise that will ensure successful conduct of the proposed r...