Among the important types of deviations of the FHR tracing from the baseline is a fetal heart “acceleration.”
These usually occur in response to fetal movement, are 15 BPM above the baseline or more, and last at least 15 seconds (a 15 x 15 acceleration). At gestational ages less than 32 weeks, these accelerations are smaller and briefer, rising 10 BPM and lasting 10 seconds.
![Fetal Heart Accelerations 1 Accelerations](https://brooksidepress.org/mil_ob_gyn/wp-content/uploads/2015/06/efm_accelerations-300x169.jpg)
Accelerations can often be provoked by stimulating the fetal scalp during a pelvic examination, or by acoustically stimulating the fetus with a loud, obnoxious noise. The presence of fetal accelerations is reassuring that the fetus is healthy and tolerating the intrauterine environment well.
![Fetal Heart Accelerations 2 Fetal Acoustic Stimulation with normal fetal heart response](https://brooksidepress.org/mil_ob_gyn/wp-content/uploads/2015/06/efm_fas-300x169.jpg)
During labor, no significance is attached to the absence of fetal accelerations.
In the event that an acceleration lasts longer than 2 minutes, then it is called a “prolonged acceleration.” If it lasts longer than 10 minutes, it is no longer considered an acceleration…it is defined as a change in baseline.