Version May 2024
| Variability |
| Fluctuations in baseline that are irregular in amplitude and frequency |
| Absent = amplitude undetectable |
| Minimal = amplitude 0 to 5 bpm |
| Moderate = amplitude 6 to 25 bpm |
| Marked = amplitude over 25 bpm |
| Measured in a 10-minute window. The amplitude is measured peak to trough. There is no distinction between short-term and long-term variability. |
| Baseline rate |
| Bradycardia = below 110 bpm |
| Normal = 110 to 160 bpm |
| Tachycardia = over 160 bpm |
| The baseline rate is the mean bpm (rounded to 0 or 5) over a 10-minute interval, excluding periodic changes, periods of marked variability, and segments that differ by more than 25 bpm. The baseline must be identifiable for two minutes during the interval (but not necessarily a contiguous two minutes); otherwise, it is considered indeterminate. |
| Acceleration |
| An abrupt* increase in the FHR. Before 32 weeks of gestation, accelerations should last ≥10 sec and peak ≥10 bpm above baseline. As of 32 weeks gestation, accelerations should last ≥15 sec and peak ≥15 bpm above baseline. |
| A prolonged acceleration is ≥2 minutes but less than 10 minutes. An acceleration of 10 minutes or more is considered a change in baseline. |
| Late deceleration |
| A gradual* decrease and return to baseline of the FHR associated with a uterine contraction. The deceleration is delayed in timing, with the nadir of the deceleration occurring after the peak of the contraction. The onset, nadir, and recovery usually occur after the onset, peak, and termination of a contraction. |
| Early deceleration |
| A gradual* decrease and return to baseline of the FHR associated with a uterine contraction. The nadir of the FHR and the peak of the contraction occur at the same time. The deceleration's onset, nadir, and termination are usually coincident with the onset, peak, and termination of the contraction. |
| Variable deceleration |
| An abrupt* decrease in FHR below the baseline. The decrease is ≥15 bpm, lasting ≥15 secs and <2 minutes from onset to return to baseline. The onset, depth, and duration of variable decelerations commonly vary with successive uterine contractions. |
| Prolonged deceleration |
| A decrease in FHR below the baseline of 15 bpm or more, lasting at least 2 minutes but <10 minutes from onset to return to baseline. A prolonged deceleration of 10 minutes or more is considered a change in baseline. |
NICHD: National Institute of Child Health and Human Development; FHR: fetal heart rate; bpm: beats per minute; sec: seconds.
* "Gradual" and "abrupt" changes are defined as taking ≥30 seconds or <30 seconds, respectively, from the onset of the deceleration/acceleration to its nadir/peak.آیا می خواهید مدیلیب را به صفحه اصلی خود اضافه کنید؟
