Abstract Body: Background. Modifiable health behaviors are key components of cardiovascular health in pregnancy and the years after delivery, but the mechanisms by which early pregnancy behaviors shape maternal health outcomes are uncertain. Allostatic load is an objective measure of cumulative psychosocial stress that uses biomarkers to quantify stress through deviations from homeostasis. We hypothesized that healthier behaviors in early pregnancy would be associated with lower cross-sectional and long-term allostatic load. Methods. This secondary analysis included participants in the nuMoM2b-HHS1 prospective cohort who completed assessments in the first trimester of pregnancy and 2-7 (mean 3.2) years following delivery (N=4,296). Self-reported physical activity, diet quality, sleep duration, and smoking history in the first trimester were scored from 0-100 (higher is healthier) using the Life’s Essential 8 algorithm. Latent profiles of behavioral combinations were empirically constructed from these scores. Allostatic load was calculated at both timepoints using a validated set of 11 biomarkers spanning the cardiovascular, inflammatory, and metabolic domains of physiology, assigning 1 point for biomarker values in timepoint-specific high-risk quartiles (score range 0-11, higher is more adverse). Associations between categorical behavioral profiles and allostatic load in the first trimester and 2-7 years following delivery were evaluated using Poisson regression with robust error variance. All models were adjusted for maternal age and self-reported race and ethnicity; the model assessing allostatic load 2-7 years following delivery was also adjusted for first trimester allostatic load. Significance was accepted at p<0.05. Results. Four latent profiles of health behavior combinations in early pregnancy were identified (Table 1): Healthy Behaviors (38%), Healthy Activity/Sleep with Poor Diet/Smoking (19%), Healthy Sleep Only (33%), and Least Healthy Behaviors (10%). Compared to the Healthy Behaviors profile, participants in profiles with lower adherence to healthy behaviors in the first trimester had 12-15% higher allostatic load in the first trimester and 10-15% higher allostatic load 2-7 years following delivery (Table 2). Conclusions. Healthy behaviors in early pregnancy are associated with lower physiological stress both in pregnancy and years following delivery. Future work will examine time-varying health behaviors and allostatic load in the context of childrearing.