Summary
Large-scale wearable studies confirm HRV decreases from pre-pregnancy through the third trimester (from ~40ms to ~30ms RMSSD), then begins recovering in the final weeks before delivery.
Methods
Apple Women's Health Study with continuous wearable monitoring
Key Findings
- HRV decreased from 39.9ms pre-pregnancy to 29.9ms in third trimester
- Heart rate increased significantly in second trimester
- HRV began rebounding in last weeks of pregnancy
- Circadian HRV patterns also change during pregnancy
- Altered HRV may predict pregnancy complications
Limitations
Normal variation significant, individual baselines matter
What This Means for You
During pregnancy, expect progressively lower HRV—this reflects normal cardiovascular adaptations. Compare to your own pregnancy baseline, not pre-pregnancy values. Alert your provider if HRV drops unusually.
Source
Read the original paper in Cell Reports Medicine ↗
Added to HRV Zone: 2025-01-10