Daily Changes in Sleep Stages and Associated Cardiovascular Parameters During Pregnancy: Using a Wearable Device

Yuqing Guo^1*Qi Xu²Laura Narvaez¹Nikil Dutt³Priscilla Kehoe¹Annie Qu²

• ¹Sue and Bill Gross School of Nursing, University of California, Irvine, Irvine, United States
• ²Department of Statistics, University of California, Irvine, Irvine, United States
• ³Departments of Computer Science, University of California, Irvine, Irvine, United States

Objective: Growing evidence links sleep disturbances with gestational hypertension and/or preeclampsia. Most studies rely on self-reported surveys that cannot capture sleep stages as objective indicators of cardiovascular health. The objective of this study was to utilize a wearable device to describe changes in nightly sleep stages during pregnancy and investigate their relationships with resting heart rate (HR) and heart rate variability (HRV). Methods: This longitudinal descriptive study encompassed 981 observation days among 14 pregnant women, 86% of whom self-identified as Hispanic. The Oura ring collected nighttime sleep and cardiovascular data every 5 minutes, including deep, Rapid Eye Movement (REM), light sleep, and awake, as well as HR and HRV. The frequency and duration of each sleep stage occurrence indicated daily sleep characteristics. Linear mixed models were employed to detect daily changes in sleep stages and to investigate their associations with cardiovascular parameters while adjusting for gestational weeks, maternal age, and pre-pregnancy body mass index. Results: Significant daily changes occurred in deep/light sleep and awake (all p < 0.05), but not in REM. The deep sleep onset significantly increased (p = 0.03), while the deep sleep occurrence frequency decreased (p < 0.001). The duration per light sleep decreased (p = 0.04) while awake increased (p = 0.009). More deep sleep was significantly associated with lower HR but higher HRV (all p values < 0.01). REM sleep had opposite patterns, associated with increased HR and decreased HRV (all p values < 0.01). Light sleep/awake showed no significant associations with HR/HRV. Discussion: This is the first study using a wearable device to describe daily associations between sleep and cardiovascular parameters during pregnancy among primarily Hispanic pregnant women. The findings suggest that non-invasive wearable devices monitoring deep sleep and parasympathetic nervous system activity could inform digital interventions on how to enhance deep sleep and promote cardiovascular health in pregnant women. Conclusion: Wearable device monitoring can identify critical changes in sleep during pregnancy, particularly the relationship whereby greater deep sleep is associated with favorable cardiovascular health markers. These findings lay the groundwork for developing personalized, technology-enabled maternal health interventions to promote cardiovascular wellness during pregnancy.