Large-Scale Analysis of Oura Ring Data During Pregnancy: Temporal Trajectories in Sleep, Temperature Trends, Cardiorespiratory, and Activity Metrics.

Background: Pregnancy and childbirth involve significant health challenges, including preventable maternal deaths, severe complications, and disparities tied to social determinants, emphasizing the need for improved maternal care. Pregnancy could benefit from a more comprehensive, continuous care model that captures dynamic changes and enhances maternal-fetal outcomes.

Objective: This large-scale, real-world, high-density study uses wearable data to investigate maternal biobehavioral trajectories for pregnancies leading to loss, preterm, and term births, exploring how demographics factors like age and body mass index (BMI) affect these trajectories.

Methods: Retrospective observational analysis of pregnancies from a sample of 10,318 18-51-year-old female Oura Ring users (324 preterm births, 5039 term births, 4955 pregnancies ending in loss before 20 weeks of gestation). Oura biobehavioral data were analyzed across a 64-week window encompassing 8 weeks pre-pregnancy, through pregnancy and postpartum, via Generalized Estimating Equation (GEE) statistical modeling.

Results: Gestational age emerged as a significant factor across all domains among term pregnancies (P < .001). During the first trimester, participants experienced marked sleep changes, peaking around week 9 and characterized by more time in bed (+30 min), asleep (+15 min), and awake (+15 min) compared to pre-pregnancy. Metrics declined and stabilized in the second trimester; by the third, time in bed returned to baseline, while sleep remained reduced and wakefulness elevated. At birth, time in bed and wakefulness peaked, and sleep duration reached its minimum, with nighttime wake exceeding 3 standard deviations above baseline. Temperature changes were more pronounced, sustained, and occurred earlier than sleep changes-becoming evident by week 4, peaking at +0.3 °C above baseline by week 9, and showing a steady decline until birth. A secondary, modest increase (+0.1 °C) was observed near birth, followed by a decline postpartum. Heart rate (HR) increased steadily, peaking at +10 bpm above baseline at week 32, while HR variability (HRV) declined by >15 ms in a mirrored pattern. Respiratory rate peaked around week 9 and declined thereafter. Step count declined in the first trimester, with a ~2,000-step reduction at around week 8. After a slight rebound mid-pregnancy, activity declined again, reaching its lowest point near birth, with >2,500 fewer steps than pre-pregnancy. Age and BMI showed significant but modest interaction effects (all P <.01). In pregnancies ending in loss, deviations emerged up to two weeks prior. Time in bed decreased starting ~2 weeks before loss (P <.001), followed by reductions in sleep duration (P <.001), temperature trends (P <.001), respiratory rate (P =.019), HR (P =.005), and awake time (P =.033).

Conclusions: These findings highlight the complex dynamics underlying changes in participants' sleep, temperature trends, cardiorespiratory, and activity data throughout pregnancy, involving extensive adaptations. A deeper focus on normative changes can advance maternal-fetal medicine, improve clinical outcomes, and address scientific gaps.

Clinicaltrial: