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Difficulty: EasyLabor, Delivery, and Puerperium

An 18-year-old nulliparous patient at 38 weeks gestation is evaluated on the labor and delivery unit. She was admitted in active labor, and artificial rupture of membranes was performed two hours ago. Her temperature is 37.0°C (98.6°F) and blood pressure is 110/70 mmHg. Cervical examination shows 7 cm dilation, 100% effacement, and the fetal vertex at +1 station. The external fetal monitor shows a baseline heart rate of 145/min with moderate variability. During the monitoring period, the fetal heart rate frequently exhibits abrupt decreases to 85/min. These decreases reach their nadir within 15 seconds of onset, last for roughly 45 seconds, and rapidly return to the baseline of 145/min. These episodes occur during the majority of her uterine contractions. Which of the following is the most appropriate initial step in management?

  1. A
    Amnioinfusion
  2. B
    Cesarean delivery
  3. Maternal repositioningAnswer
  4. D
    Intravenous oxytocin
  5. E
    Subcutaneous terbutaline

Answer

Maternal repositioning
The patient's fetal heart rate (FHR) tracing demonstrates variable decelerations. Variable decelerations are visually defined by an abrupt decrease in the FHR (onset to nadir in less than 30 seconds) of at least 15 beats per minute, lasting at least 15 seconds, and returning to baseline in less than 2 minutes. They are caused by umbilical cord compression, a complication that is particularly common after the rupture of membranes reduces the cushioning effect of the amniotic fluid. The most appropriate initial step in management is maternal repositioning (e.g., placing the patient in the lateral decubitus position). This non-invasive maneuver shifts the position of the fetus and the uterus, frequently relieving the mechanical compression on the umbilical cord and restoring normal umbilical blood flow.

Step-by-Step Solution

1
Analyze the fetal heart rate (FHR) tracing characteristics.
The FHR shows abrupt decreases (nadir reached in < 30 seconds) that drop ≥ 15/min below baseline and last ≥ 15 seconds, identifying them as variable decelerations.
Accurate identification of the deceleration type is required to determine the underlying pathophysiology.
2
Determine the physiological cause of the decelerations.
Variable decelerations are caused by umbilical cord compression, which frequently occurs after membrane rupture reduces the protective cushioning of amniotic fluid.
Understanding the etiology dictates whether the issue can be resolved with positional changes or requires medical intervention.
3
Select the appropriate first-line management step.
Maternal repositioning (e.g., to the left or right lateral decubitus position) is selected as the initial intervention.
Intrauterine resuscitation protocols dictate starting with the least invasive maneuver to relieve mechanical pressure on the cord before escalating to procedures like amnioinfusion.

Key Concept

Variable fetal heart rate decelerations are caused by umbilical cord compression and should initially be managed with non-invasive maternal repositioning.
Estimated Time:1m 0s
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Topics

Labor, Delivery, and Puerperium

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