QCOM
Quillen College of Medicine, East Tennessee State University


Acceleration

 

A visually apparent increase (onset to peak in less than 30 sec) in the FHR from the most recently calculated baseline
- The duration of an acceleration is defined as the time from the initial change in FHR from the baseline to the return of the FHR to the baseline
- At 32 weeks of gestation and beyond, an acceleration has an acme of 15 beats per min or more above baseline, with a duration of 15 sec or more but less than 2 min
- Before 32 weeks of gestation, an acceleration has an acme of 10 beats per min or more above baseline, with a duration of 10 sec or more but less than 2 min
- Prolonged acceleration lasts 2 min or more, but less than 10 min
- If an acceleration lasts 10 min or longer, it is a baseline change

(NICHD)


Accelerations of the FHR may be periodic (that is, occurring in relation to a contraction) or episodic (no association with a contraction). Most are episodic. These episodic accelerations are generally in response to fetal movement, with a need for increased perfusion, and therefore transiently increased sympathetic tone, or due to fetal stimulation, such as scalp stimulation with a vaginal exam, abdominal palpation, or vibroacoustic stimulation.

Periodic accelerations are those associated with uterine contractions and may be due either to fetal stimulation (particularly in breech presentation) or due to mild cord compression (that is, compression of the umbilical vein only).

FHR accelerations and good (moderate) variability are closely associated and sometimes may be visually indistinguishable, though both are reflective of a well-oxygenated fetus.

The presence of accelerations forms the basis of the nonstress test (NST). An NST is said to be reactive when there are at least two accelerations in a 20 minute period, along with moderate variability and no decelerations.

Below is an example of fetal acceleration.  Please click to enlarge.

Acceleration Video 1

Acceleration Video 2

Acceleration Video 3

Acceleration Video 4

 


 

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