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Poster Session 4

Category: Physiology/Endocrinology

Poster Session 4

(1202) Three Phenotypes of Maternal Heart Rate Adaptation During the First Postpartum Year

Thursday, February 12, 2026

3:30 PM - 5:00 PM

Submitting Author and Presenting Author(s)

Natalie M. Williams, BS (she/her/hers)

Medical Student (MS3)
Washington State University Elson S. Floyd College of Medicine
Kennewick, Washington, United States

Coauthor(s)

TL

Teresa Lillis, PhD

Rush University Medical Center
Chicago, Illinois, United States
DH

Devon Hansen, PhD

Washington State University Sleep and Performance Research Center
Spokane, Washington, United States

Objective:
Wearable data offers unique windows into perinatal cardiovascular adaptation. Previous studies show heart rate (HR) decreases after delivery and stabilizes by 3-12 months postpartum. However, daily HR patterns across the preconception–postpartum arc remain undescribed. We leveraged two years of wearable HR data to determine whether distinct adaptation trajectories emerged across the postpartum.

Study Design:
Twenty-four primiparous women (26-43 y) contributed daily HR data from 12 months pre-conception through 12 months postpartum and completed surveys capturing subsequent pregnancies. Each participant's mean HR across three preconception months defined their baseline. Daily HR "difference scores" (daily HR minus baseline) were cumulatively summed to generate HR-change curves. Data-driven clustering identified groups with similar curves.

Results:
^{HR curves during preconception oscillated around baseline; most participants showed monotonic increases across pregnancy. Postpartum, three trajectory groups emerged (Figure 1): "Sustained-Low" (n=9) rapidly declined following birth and remained below baseline throughout the postpartum year; "Recovery-to-Plateau" (n=9) declined rapidly then plateaued by ~6 months; "Rebound-High" (n=5) showed initial decline then subsequent HR increase beginning ~6 months postpartum. Every "Rebound-High" participant conceived again within 6–9 months postpartum; no additional postpartum pregnancies occurred in other groups.}

Conclusion:
Daily wearable HR data uncovered three distinct postpartum adaptation phenotypes. Most notably, short interpregnancy interval (IPI < 12 months) showed complete association with a rebound pattern, with every participant conceiving again within 6–9 months, showing renewed HR elevation ~6 months postpartum. This represents the first continuous monitoring evidence that IPI timing correlates with distinct cardiovascular adaptation patterns. These findings warrant further investigation into the relationship between HR trajectory phenotypes and maternal health outcomes.