Review Question - QID 217617

This pregnant patient presents at 38 weeks of gestation with spontaneous rupture of membranes. The fetal heart tracing shows decreases in fetal heart rate that occur following the apex of a contraction (late decelerations), that are indicative of uteroplacental insufficiency.

Late decelerations are defined as decelerations in fetal heart rate that occur following the apex of a uterine contraction. These decelerations are gradual (duration of onset of the deceleration to the nadir of the deceleration is >30 seconds). Late decelerations are a sign of uteroplacental insufficiency and are viewed as potentially dangerous, as they can be associated with a variety of causes of fetal distress. For example, late decelerations may occur in the setting of placental abruption, maternal diabetes, maternal sepsis, or any condition which causes insufficient blood flow to the uterus or placenta. Late decelerations may also occur in the setting of post-term pregnancies. Repetitive late decelerations require urgent intervention. First-line treatment consists of intrauterine resuscitation (e.g., maternal repositioning, intravenous fluids) and scalp stimulation to induce an acceleration, whereas persistent late decelerations require Cesarean section.

Nageotte reviewed the application of fetal heart rate monitoring in the clinical setting. They found that though there is little evidence for its efficacy, its use is widespread. They recommended that healthcare providers understand the pathophysiology underlying fetal heart rate monitoring in order to interpret findings and optimize patient outcomes.

Figure/Illustration A show a fetal heart tracing showing late decelerations (blue arrow), in which the fetal heart rate decreases following the apex of the contraction (red arrow).

Incorrect Answers:
Answer 1: Acidosis of the fetus may cause a sinusoidal tracing on fetal heart monitoring if severe. In this pattern, the fetal heart rate oscillates, appearing like a sine wave. This finding on fetal heart tracing indicates significant fetal anemia, hypoxia, or acidosis and requires urgent intervention with resuscitation (e.g., maternal repositioning, intravenous fluids) and delivery. Opioid use has also been reported to cause sinusoidal fetal heart tracings.

Answer 2: Head compression of the fetus may cause early decelerations, which are characterized by decreases in fetal heart rate that co-occur with the apex of a uterine contraction. Early decelerations are typically a benign finding.

Answer 3: Infection of the amniotic fluid, or chorioamnionitis, typically causes maternal fever and acceleration of the fetal heart rate. Though this patient had spontaneous rupture of membranes with meconium-stained fluid which increases the risk of chorioamnionitis, there is no evidence of chorioamnionitis (e.g., maternal fever, uterine tenderness). Treatment is with prompt broad spectrum antibiotic administration and delivery.

Answer 4: Umbilical cord compression may present with variable decelerations, which are characterized by abrupt decreases in fetal heart rate. They can be easily distinguished from late decelerations by the rapid return to the baseline heart rate. These typically respond to maternal repositioning.

Bullet Summary:
Late decelerations are decreases in fetal heart rate that occur following the apex of a contraction and indicate uteroplacental insufficiency.