Key result
During pregnancy, daily heart rate variability steadily decreased and resting heart rate increased, but these trends reversed 49 days prior to birth with a steady increase in HRV and decrease in RHR.
Why the study?
Characterizing normal HRV and RHR during pregnancy using continuous wearable technology allows for further investigation into disease states, given known decreases in cardiovascular health during pregnancy.
How do heart rate variability and resting heart rate change in healthy women across the perinatal period when monitored continuously with wearable technology?
Cohort (n=18)
No
How do heart rate variability and resting heart rate change in healthy women across the perinatal period when monitored continuously with wearable technology?
Effect estimate: HRV Est. = -0.10; RHR Est. = 0.05
p-value: p=<0.0001
Continuous wearable monitoring reveals significant changes in HRV and RHR throughout pregnancy, including a rapid reversal of trends 49 days prior to birth, which is moderated by physical activity.
Wearable HRV/RHR monitoring detects perinatal autonomic shifts; hypothesis-generating and requires prospective validation before clinical use.
BACKGROUND Characterizing normal heart rate variability (HRV) and resting heart rate (RHR) in healthy women over the course of a pregnancy allows for further investigation into disease states, as pregnancy is the ideal time period for these explorations due to known decreases in cardiovascular health. To our knowledge, this is the first study to continuously monitor HRV and RHR using wearable technology in healthy pregnant women. METHODS A total of eighteen healthy women participated in a prospective cohort study of HRV and RHR while wearing a WHOOP® strap prior to conception, throughout pregnancy, and into postpartum. The study lasted from March 2019 to July 2021; data were analyzed using linear mixed models with splines for non-linear trends. RESULTS Eighteen women were followed for an average of 405.8 days (SD=153). Minutes of logged daily activity decreased from 28 minutes pre-pregnancy to 14 minutes by third trimester. A steady decrease in daily HRV and increase in daily RHR were generally seen during pregnancy (HRV Est. = -0.10, P <0.0001; RHR Est. = 0.05, P <0.0001). The effect was moderated by activity minutes for both HRV and RHR. However, at 49 days prior to birth there was a reversal of these indices with a steady increase in daily HRV (Est.=0.38, P < 0.0001) and decrease in daily RHR (Est. = -0.23, P < 0.0001), regardless of activity level, that continued into the postpartum period. CONCLUSIONS In healthy women, there were significant changes to HRV and RHR throughout pregnancy, including a rapid improvement in cardiovascular health prior to birth that was not otherwise known. Physical activity minutes of any type moderated the known negative consequences of pregnancy on cardiovascular health. By establishing normal changes using daily data, future research can now evaluate disease states as well as physical activity interventions during pregnancy and their impact on cardiovascular fitness.
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Rowan et al. (2022) conducted a cohort in Healthy pregnancy (n=18). Pregnancy and physical activity vs. Pre-pregnancy baseline was evaluated on Daily heart rate variability (HRV) and resting heart rate (RHR) changes (HRV Est. = -0.10; RHR Est. = 0.05, p=<0.0001). During pregnancy, daily heart rate variability steadily decreased and resting heart rate increased, but these trends reversed 49 days prior to birth with a steady increase in HRV and decrease in RHR.
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