Oura has published findings from one of the largest longitudinal analyses of pregnancy-related physiological changes, using data from more than 10,000 pregnancies tracked with Oura Ring. The study, published in JMIR mHealth and Uhealth, examined how key health metrics evolve from preconception through pregnancy and postpartum.
The research analyzed anonymized data from Oura Ring Gen3 users who self-reported pregnancies between May 2023 and November 2024. The dataset included 5,039 term births, 324 preterm births, and 4,955 pregnancies ending in loss before 20 weeks of gestation.
Researchers tracked sleep patterns, resting heart rate, heart rate variability, respiratory rate, activity levels and body temperature to identify physiological trajectories across pregnancy stages.
Key findings include a body temperature increase of 0.3°C above baseline by week 9 of pregnancy, with a steady decline until birth. Resting heart rate increased by 10 bpm above baseline at week 32, while heart rate variability declined by more than 15 milliseconds in a mirrored pattern. Sleep duration increased by approximately 15 minutes in the first trimester before declining and reaching its minimum around birth.
The study identified subtle early differences in participants who experienced pregnancy loss. These individuals showed a flatter temperature increase, lower sleep duration, and reversal of increases in respiratory rate and resting heart rate up to two weeks before pregnancy ended, compared to those who continued to term births.
“It may seem surprising, but this research is one of the few papers that even begins to describe what is considered normal for a pregnancy,” Chris Curry, Oura’s Clinical Director of Women’s Health said. “What is exciting about this science is that once we establish and validate what a healthy baseline is, we can explore the patterns that may be linked to risk of diseases.”
The company noted that wearable data cannot be used as a diagnostic tool for pregnancy health. However, the research team aims to explore how continuous physiological monitoring could help clinicians identify risks earlier and inform personalized care throughout pregnancy and postpartum.
Activity levels showed a progressive decrease from pre-pregnancy baseline until delivery, while respiratory rate peaked around week 9 before declining. Following birth, respiratory rate dropped below baseline levels.
