Review Question - QID 219720

This patient has no significant complications during pregnancy and is found to have variable decelerations on fetal heart rate monitoring. The most likely cause of these findings is umbilical cord compression.

Fetal heart rate monitoring is a method of assessing fetal well-being. A normal fetal heart ranges between 120-160/min. Accelerations of increased heart rate should also be observed with at least 15/min above baseline for ≥ 15 seconds and < 2 minutes in a 20-minute period when gestational age is > 32 weeks. The presence of at least 2 accelerations would be considered a reactive non-stress test and indicates fetal well-being. Decelerations in fetal heart rate are also associated with fetal conditions such as head compression, cord compression, or uteroplacental insufficiency. Interventions depend upon the findings that are observed on fetal heart rate monitoring. For example, variable decelerations due to umbilical cord compression findings can be corrected by shifting the maternal position or amnioinfusion if membranes have ruptured.

Pillai and James review the evidence regarding the use of fetal heart rate monitoring. They discuss how variability, accelerations, and decelerations can be used to monitor fetal well-being. They recommend being familiar with the range of normal findings so that abnormal tracings can be intervened upon expeditiously.

Figure/Illustration A is a representation of a fetal heart rate tracing demonstrating variable decelerations (red circles) that are not reliably associated with uterine contractions. These findings can be caused by umbilical cord compression.

Incorrect Answers:
Answer 1: Fetal anemia would present with a sinusoidal fetal heart rate monitoring trace. This condition is associated with significantly increased fetal morbidity and mortality. Treatment is with emergent delivery of the fetus when it is past the threshold of viability.

Answer 2: Fetal head compression would present with early decelerations where the decreases in heart rate coincide with the beginning of uterine contractions. They result from a vagal response to head compression. This response is physiologic and is not harmful to the fetus.

Answer 3: Quiet fetal heart cycles are associated with minimal variability and no accelerations and represent a sleep cycle. These cycles are physiologic and do not require intervention.

Answer 5: Uteroplacental insufficiency would present with late decelerations that start after the beginning of uterine contraction. Causes include placental abruption, maternal diabetes, maternal anemia, and maternal sepsis. Treatment for repetitive late decelerations is with emergent interventions as late decelerations are harmful to the fetus and can lead to fetal demise.

Bullet Summary:
Variable decelerations in fetal heart rate monitoring are associated with umbilical cord compression.