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Difficulty: EasyLabor, Delivery, and Puerperium

A 24-year-old primigravid woman at 39 weeks gestation is evaluated on the labor and delivery unit. She is in spontaneous active labor following an uncomplicated prenatal course. Her temperature is 37.1°C (98.8°F), blood pressure is 118/76 mm Hg, and pulse is 82/min. Cervical examination reveals 7 cm dilation, 100% effacement, and +1 station. Continuous electronic fetal monitoring demonstrates a baseline heart rate of 145/min with moderate variability. There are periodic, symmetric, gradual decreases in the fetal heart rate that begin exactly as the uterine contractions start, reach their nadir at the peak of the contractions, and return to baseline as the contractions end. The lowest heart rate recorded during these episodes is 125/min. What is the most appropriate next step in the management of this patient?

  1. Continue current expectant managementAnswer
  2. B
    Administer a short-acting tocolytic agent
  3. C
    Infuse intrauterine isotonic fluid
  4. D
    Change the maternal laboring position
  5. E
    Prepare for an urgent operative delivery

Answer

Continue current expectant management
The correct response is to continue expectant management. The clinical vignette describes a classic Category I fetal heart rate (FHR) tracing with early decelerations. Early decelerations are characterized by a gradual decrease in the FHR (onset to nadir ≥30 seconds) that is perfectly symmetric with the uterine contraction; the nadir of the deceleration occurs exactly at the peak of the contraction. This pattern is a benign, physiologic reflex caused by fetal head compression as the fetus descends through the birth canal. The compression alters cerebral blood flow, stimulating the vagus nerve and temporarily slowing the heart rate. Because early decelerations are not associated with fetal hypoxia or acidemia, no intrauterine resuscitation or alteration in the delivery plan is required.

Step-by-Step Solution

1
Analyze the described fetal heart rate (FHR) tracing characteristics.
The baseline (145/min) and variability (moderate) are normal. There are gradual decelerations that perfectly mirror the uterine contractions in timing.
Accurate interpretation of the FHR tracing is required to classify it and determine if the fetus is experiencing distress.
2
Correlate the specific FHR deceleration pattern with its underlying physiologic or pathologic etiology.
Symmetric, gradual decelerations with a nadir aligning with the peak of the contraction are defined as early decelerations, which result from fetal head compression.
Differentiating between early (head compression), variable (cord compression), and late (uteroplacental insufficiency) decelerations dictates the clinical approach.
3
Determine the appropriate management based on the etiology of the decelerations.
Because early decelerations are a benign reflex mediated by increased vagal tone and do not indicate fetal hypoxia, no intervention is needed. Expectant management should be continued.
Unnecessary interventions must be avoided in reassuring, Category I fetal heart rate tracings.

Key Concept

Early decelerations are a benign, physiologic fetal heart rate pattern caused by fetal head compression during uterine contractions and require expectant management.
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Topics

Labor, Delivery, and Puerperium

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