Maternity Nursing: Intrapartum Q 42
Which of the following findings meets the criteria of a reassuring FHR pattern?
A. FHR does not change as a result of fetal activity.
B. Average baseline rate ranges between 100 – 140 BPM.
C. Mild late deceleration patterns occur with some contractions.
D. Variability averages between 6 – 10 BPM.
Correct Answer: D. Variability averages between 6 – 10 BPM.
Variability indicates a well-oxygenated fetus with a functioning autonomic nervous system. 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 A: FHR should accelerate with fetal movement. The FHR is controlled by the autonomic nervous system. The inhibitory influence on the heart rate is conveyed by the vagus nerve, whereas excitatory influence is conveyed by the sympathetic nervous system. Progressive vagal dominance occurs as the fetus approaches term and, after birth, results in a gradual decrease in the baseline FHR. Stimulation of the peripheral nerves of the fetus by its own activity (such as movement) or by uterine contractions causes acceleration of the FHR.
Option B: Baseline range for the FHR is 120 to 160 beats per minute. 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 C: Late deceleration patterns are never reassuring, though early and mild variable decelerations are expected, reassuring findings. Late decelerations are associated with uteroplacental insufficiency and are provoked by uterine contractions. Any decrease in uterine blood flow or placental dysfunction can cause late decelerations. Maternal hypotension and uterine hyperstimulation may decrease uterine blood flow. Postdate gestation, preeclampsia, chronic hypertension, and diabetes mellitus are among the causes of placental dysfunction. Other maternal conditions such as acidosis and hypovolemia associated with diabetic ketoacidosis may lead to a decrease in uterine blood flow, late decelerations, and decreased baseline variability.