Physiological Integrity Q 27
Which of the following is a characteristic of a reassuring fetal heart rate pattern?
A. A fetal heart rate of 170–180 bpm
B. A baseline variability of 25–35 bpm
C. Ominous periodic changes
D. Acceleration of FHR with fetal movements
Correct Answer: D. Acceleration of FHR with fetal movements
Accelerations with movement are normal. Accelerations are transient increases in the FHR. They are usually associated with fetal movement, vaginal examinations, uterine contractions, umbilical vein compression, fetal scalp stimulation or even external acoustic stimulation. The presence of accelerations is considered a reassuring sign of fetal well-being.
Option A: The average fetal heart rate is between 110 and 160 beats per minute. The normal FHR range is between 120 and 160 beats per minute (bpm). The baseline rate is interpreted as changed if the alteration persists for more than 15 minutes. Prematurity, maternal anxiety and maternal fever may increase the baseline rate, while fetal maturity decreases the baseline rate.
Option B: Baseline variability is defined as fluctuations in the fetal heart rate of more than 2 cycles per minute. Marked variability is at >25 BPM. The FHR is under constant variation from the baseline. This variability reflects a healthy nervous system, chemoreceptors, baroreceptors and cardiac responsiveness. Prematurity decreases variability; therefore, there is little rate fluctuation before 28 weeks. Variability should be normal after 32 weeks.
Option C: If there are ominous periodic changes, it would indicate an abnormality in the fetal heart rate pattern. Fetal hypoxia, congenital heart anomalies and fetal tachycardia also cause decreased variability. Beat-to-beat or short-term variability is the oscillation of the FHR around the baseline in amplitude of 5 to 10 bpm. Long-term variability is a somewhat slower oscillation in heart rate and has a frequency of three to 10 cycles per minute and an amplitude of 10 to 25 bpm.