Monitoring Fetal Heart Rate
Fetal Heart Rate
I’d like to spend the next few minutes talking a little bit about fetal heart rate and the variability that enters into that when monitoring a fetal heart rate. When we think about that, in order to determine the variability in a fetal heart rate, you first have to establish a baseline.
A baseline is established by taking a 10-minute strip, a reading for 10 minutes, of the fetal heart rate and finding, within that ten minutes, two minutes in which there is a consistency in the heartbeat. No marked variability, nor do you pay attention to parts of that 10-minute strip that might include episodic or periodic changes due to various factors.
You’re looking for two minutes of a heartbeat that is more or less consistent falling within this range between absent and moderate in terms of changes to the heart rate. When establishing your baseline, you take the 10-minute strip, find the two minutes where there is basic consistency in the fetal heart rate (no episodic or periodic impingements on it), no marked changes (marked is basically change by 25 heartbeats or more per minute).
We’re going to establish the baseline then by looking at the 10-minute strip and finding the two minutes there. Then, from that baseline, you can look at the whole strip and determine what sort of variability there is in the fetal heart rate. You would categorize it in one of the four ways.
The first way is absent. This basically means there is no variability discernible, no change in the baseline amplitude whatsoever. A minimal variability would be no more than five. It would be five or less heart beats per minute change between the baseline that’s been established.
A moderate variability would be between six and 25 heart beats per minute change or difference between the baseline that you’ve established. Finally, marked variability in the fetal heart rate would be greater than 25 heart beats per minute change.
It’s important that you know this range, this categorization of the fetal heart rate, in order that you might accurately determine the variability and establish the baseline in monitoring fetal heart rates.