Normal fhr
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normal fetal heart rate range bpm obstetrics
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Normal Fetal Heart Rate (FHR)
Baseline FHR
- Normal range: 110 - 160 beats per minute (bpm)
- This is assessed over a 10-minute window, excluding accelerations and decelerations
Abnormal Variants
| Term | Definition |
|---|---|
| Bradycardia | Baseline FHR < 110 bpm |
| Tachycardia | Baseline FHR > 160 bpm |
Normal FHR Characteristics (on CTG/Cardiotocography)
| Feature | Normal (Reassuring) |
|---|---|
| Baseline | 110 - 160 bpm |
| Baseline variability | 5 - 25 bpm |
| Accelerations | Present (≥ 15 bpm rise, lasting ≥ 15 seconds) |
| Decelerations | Absent (or early decelerations only) |
Key Points
- Variability reflects the beat-to-beat variation and indicates a healthy, responsive autonomic nervous system
- Accelerations are a sign of fetal well-being and an intact central nervous system
- Early decelerations (mirror uterine contractions) are benign - caused by head compression
- Late decelerations (after the contraction peak) are non-reassuring - suggest uteroplacental insufficiency
- Variable decelerations are caused by cord compression
FHR Changes with Gestational Age
- Earlier in gestation, the baseline tends to be slightly higher (closer to 160)
- As the fetus matures, the vagal tone increases and the rate tends to fall toward the lower end of normal
Clinical Significance
A reactive non-stress test (NST) requires:
- At least 2 accelerations of ≥ 15 bpm lasting ≥ 15 seconds within a 20-minute window
- This indicates fetal well-being
Note from ACOG/NICE guidelines: A normal (Category I) CTG trace shows a baseline of 110-160 bpm, moderate variability (6-25 bpm), no late or variable decelerations, and presence of accelerations.
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