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Difficulty: MediumLabor, Delivery, and Puerperium

A 25-year-old primigravida at 38 weeks gestation is evaluated in the labor and delivery unit for active labor. Her pregnancy has been uncomplicated. Her temperature is 37.0°C (98.6°F), blood pressure is 118/76 mm Hg, and pulse is 82/min. Cervical examination reveals 5 cm dilation, 100% effacement, and 0 station. Artificial rupture of membranes was performed 1 hour ago, yielding clear amniotic fluid. Uterine contractions are occurring every 3 to 4 minutes and palpate as strong. External fetal monitoring shows a baseline heart rate of 140/min with moderate variability. Over the last 30 minutes, there are abrupt decreases in the fetal heart rate to 85/min that last for 40 to 50 seconds before rapidly returning to baseline. These decreases occur in association with 60% of the uterine contractions, and their timing varies relative to the peak of the contractions. The patient is currently positioned in the left lateral decubitus position and is receiving a bolus of intravenous lactated Ringer solution, but the fetal heart rate pattern remains unchanged. Which of the following is the most appropriate next step in management?

  1. Initiation of amnioinfusionAnswer
  2. B
    Immediate cesarean delivery
  3. C
    Administration of intravenous terbutaline
  4. D
    Placement of a fetal scalp electrode
  5. E
    Continuation of current management without intervention

Answer

Initiation of amnioinfusion
The patient's external fetal heart rate tracing demonstrates recurrent variable decelerations. Variable decelerations are defined by an abrupt decrease in the fetal heart rate (onset to nadir < 30 seconds) and are typically caused by umbilical cord compression. They are considered recurrent when they occur with 50% or more of uterine contractions in a 20-minute window. Initial management involves intrauterine resuscitation techniques, including maternal repositioning (to physically shift the fetus off the cord) and intravenous fluid administration. Because this patient is already receiving these interventions without improvement, and her membranes are already ruptured, the next best step is the initiation of an amnioinfusion. Amnioinfusion involves the transcervical instillation of normal saline or lactated Ringer solution directly into the amniotic cavity. This procedure artificially increases the amniotic fluid volume, providing a protective cushion around the umbilical cord, thereby relieving compression and decreasing the likelihood of requiring a cesarean delivery for an abnormal FHR tracing.

Step-by-Step Solution

1
Analyze the fetal heart rate (FHR) tracing to identify the pattern.
The FHR shows abrupt decreases (<30 seconds from onset to nadir) that vary in timing with contractions, indicating variable decelerations.
Accurate interpretation of the FHR tracing is required to determine the underlying pathophysiology, which in this case is umbilical cord compression.
2
Determine the severity and frequency of the decelerations.
The variable decelerations are classified as recurrent because they occur with >50% of uterine contractions over a 30-minute period.
Recurrent variable decelerations require active intervention to prevent progressive fetal hypoxemia and acidemia.
3
Evaluate the response to initial intrauterine resuscitation.
The patient is already in the left lateral decubitus position and receiving IV fluids, but the decelerations persist.
Initial conservative measures have failed to alleviate the cord compression.
4
Select the next appropriate intervention based on standard management guidelines.
Amnioinfusion is indicated to artificially increase amniotic fluid volume and relieve umbilical cord compression.
Amnioinfusion is the next appropriate step for recurrent variable decelerations unresponsive to initial measures in a patient with ruptured membranes, before resorting to cesarean delivery.

Key Concept

Recurrent variable decelerations are typically caused by umbilical cord compression and are managed first with maternal repositioning and IV fluids, followed by amnioinfusion if initial measures fail.
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Topics

Labor, Delivery, and Puerperium

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