Oura Ring Pregnancy: Heart Rate, Temperature, and Sleep

Tracking physiological changes during pregnancy provides valuable insights into maternal health. Wearable devices like the Oura Ring offer continuous monitoring of key metrics, helping individuals observe shifts in heart rate, temperature, sleep, and overall well-being.

Understanding these patterns helps expectant mothers recognize trends in their body’s responses. The following sections explore specific physiological changes detected by the Oura Ring during pregnancy.

Heart Rate Patterns

During pregnancy, the cardiovascular system adapts to support fetal development, and these changes are reflected in heart rate patterns. The Oura Ring tracks heart rate variability (HRV) and resting heart rate (RHR), offering insights into these shifts. Research indicates that RHR begins rising early in pregnancy, often increasing by 10–20 beats per minute (bpm) by the third trimester (Meah et al., 2020). This elevation results from increased blood volume, hormonal fluctuations, and growing metabolic demands.

As RHR rises, HRV decreases, reflecting heightened sympathetic nervous system activity, which helps regulate blood pressure and cardiac output (Klinkenberg et al., 2021). HRV tends to be lowest in the third trimester, marking peak physiological strain before delivery (Bruno et al., 2022).

Nocturnal heart rate also increases, likely due to progesterone’s effects on thermoregulation and cardiovascular function (Pereira et al., 2020). The Oura Ring tracks these overnight patterns, potentially offering early indications of pregnancy progression. Some studies suggest deviations from expected heart rate trends—such as an unusually high RHR or a sudden HRV drop—may signal complications like gestational hypertension or preeclampsia (Fu et al., 2021).

Core Temperature Fluctuations

Core body temperature shifts during pregnancy due to hormonal changes and metabolic adjustments. The Oura Ring tracks deviations from an individual’s baseline, providing a continuous record of these fluctuations. After conception, progesterone raises basal temperature by 0.2°C to 0.5°C, a trend that persists through the first trimester (Silva et al., 2020).

As pregnancy progresses, metabolic rate increases by 15–20%, generating additional heat (Pires et al., 2021). Pregnant individuals often experience sustained nightly temperature elevations as the body adjusts to support fetal growth.

By the third trimester, blood volume expands nearly 50% (Meah et al., 2020), affecting heat distribution and contributing to temperature variability. Some studies suggest fluctuations become more pronounced in the weeks before delivery, possibly signaling the body’s preparation for labor (Bai et al., 2022). The Oura Ring’s real-time tracking offers insights into these physiological transitions.

Respiratory Rate Dynamics

Pregnancy alters respiratory physiology to meet increased oxygen demands. One of the earliest changes is an increase in tidal volume—the amount of air moved per breath—due to progesterone’s role as a respiratory stimulant. This results in mild hyperventilation and a 40% rise in minute ventilation (Hegewald & Crapo, 2020). Despite this, respiratory rate remains relatively stable, typically between 12–20 breaths per minute.

As pregnancy progresses, the expanding uterus shifts the diaphragm upward, reducing lung compliance and altering ventilation distribution. This can create a sensation of breathlessness, particularly during exertion, though lung function remains preserved (LoMauro & Aliverti, 2019). The Oura Ring tracks nighttime respiratory rate variations, offering insights into how these changes manifest over time.

Increased metabolic rate also raises oxygen consumption by 20–30% to support fetal growth (Powell & Carnegie, 2020). This leads to lower arterial carbon dioxide levels, creating mild respiratory alkalosis. While this is a normal adaptation, sudden respiratory rate increases or irregular patterns may indicate conditions such as gestational anemia or respiratory compromise.

Sleep Characteristics

Pregnancy significantly impacts sleep quality, architecture, and duration. The Oura Ring monitors these changes, revealing increased sleep fragmentation as pregnancy progresses. Rising progesterone levels contribute to excessive daytime sleepiness in the first trimester, often leading to longer nighttime sleep. However, by the third trimester, sleep efficiency declines due to frequent awakenings caused by physical discomfort, nocturnal urination, and metabolic shifts. Total sleep time can decrease by up to an hour per night in late pregnancy, with a reduction in restorative deep sleep (Facco et al., 2018).

Pregnancy also alters sleep stage distribution. Rapid eye movement (REM) sleep declines in later pregnancy, likely due to increased sympathetic nervous system activity and frequent awakenings. Lighter sleep stages, particularly N1 and N2, become more dominant, possibly as an adaptive response to heightened physiological stress. The Oura Ring’s sleep tracking provides insights into these shifts, helping expectant mothers recognize changes in their sleep cycles.

Activity Patterns

Physical activity declines during pregnancy due to physiological changes, evolving energy demands, and increasing physical constraints. The Oura Ring tracks movement patterns, step count, and activity levels, providing a detailed picture of these adjustments. Many pregnant individuals experience a gradual decline in moderate-to-vigorous activity, primarily due to fatigue, musculoskeletal discomfort, and weight gain. While the American College of Obstetricians and Gynecologists (ACOG) recommends at least 150 minutes of moderate-intensity exercise per week, adherence often becomes more challenging in later trimesters.

Daily step counts recorded by the Oura Ring highlight these shifts, showing reductions in mobility, particularly in the third trimester when pelvic girdle pain and swelling increase. Tracking these changes helps individuals adjust activity levels based on comfort and energy availability. The Oura Ring’s readiness score, which factors in HRV, temperature, and activity load, can further guide adjustments by indicating recovery status and potential strain.