How Pregnancy Alters Sleep Patterns and Vital Signs Across Trimesters

Pregnancy causes major shifts in the human body that affect biometrics like heart rate, sleep, and body temperature. Dr Chris Curry, an OB/GYN and clinical director of Women's Health at Oura, shared details on these transformations in an interview with HT Lifestyle.

First Trimester

Sleep patterns change early in pregnancy. Research shows participants spent over 30 minutes more in bed each night during the first trimester, but only gained about 15 minutes of actual sleep. Factors like nausea and frequent bathroom trips make it hard to stay asleep. Body temperature and breathing rate also start to rise within the first few weeks, while resting heart rate and heart rate variability begin to shift from pre-pregnancy levels.

Second and Third Trimesters

Time spent in bed drops in the second trimester and stays steady. The cardiovascular system adapts as resting heart rate steadily increases and heart rate variability steadily decreases. By the third trimester, time in bed matches pre-pregnancy levels, but more time is spent awake, leading to less actual sleep. This trend lasts until birth, when time in bed peaks and sleep time hits its lowest point due to physical discomfort, frequent urination, and anticipation.

Postpartum Phase

After delivery, total time in bed drops sharply compared to pre-pregnancy levels, and time spent awake in bed increases. Newborn feeding and sleep routines heavily influence the mother's biometrics during this time. Meanwhile, resting heart rate and heart rate variability quickly return toward pre-pregnancy baselines within days of delivery.

Context

Pregnancy places heavy demands on a woman's cardiovascular and endocrine systems, forcing the heart and metabolism to work harder to support a developing fetus. Monitoring vital signs like resting heart rate and sleep patterns offers medical professionals clear insights into how well a mother's body is adapting to these physical stresses.