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Difficulty: MediumLabor, Delivery, and Puerperium

A 29-year-old nulliparous woman at 39 weeks gestation is evaluated in the labor and delivery unit due to a concerning fetal heart rate tracing. Her pregnancy has been uncomplicated. She was admitted in active labor and her cervix is currently 7 cm dilated and 100% effaced, with the fetal presenting part at +1 station. Uterine contractions are occurring every 2 to 3 minutes, each lasting approximately 60 seconds. Spontaneous rupture of membranes occurred 2 hours ago, revealing clear fluid. The continuous electronic fetal monitor demonstrates a baseline heart rate of 135/min with moderate variability. With each of the last four contractions, there is an abrupt decrease in the fetal heart rate to 85/min that reaches its nadir in 15 seconds and resolves quickly as the contraction subsides. The decelerations last approximately 45 seconds each. The patient is promptly repositioned to the left lateral decubitus position and administered an intravenous fluid bolus. However, the subsequent three contractions demonstrate the exact same fetal heart rate pattern. Maternal blood pressure is 118/76 mm Hg and pulse is 88/min. Which of the following is the most appropriate next step in management?

  1. A
    Administration of subcutaneous terbutaline
  2. B
    Emergency cesarean delivery
  3. Initiation of an amnioinfusionAnswer
  4. D
    Augmentation with intravenous oxytocin
  5. E
    Continued expectant management

Answer

Initiation of an amnioinfusion
The correct answer is the initiation of an amnioinfusion. This patient's fetal heart rate tracing demonstrates recurrent variable decelerations, defined as visually apparent abrupt decreases in heart rate (onset to nadir less than 30 seconds) lasting between 15 seconds and 2 minutes, occurring with more than 50% of uterine contractions. Variable decelerations are typically caused by umbilical cord compression, which can occur due to oligohydramnios, cord prolapse, or normal descent of the fetus. Initial intrauterine resuscitation for recurrent variable decelerations includes maternal repositioning (to relieve mechanical cord compression) and intravenous fluid boluses. Because this patient's decelerations persist despite these first-line maneuvers, the next best step is an amnioinfusion. This procedure involves instilling normal saline or lactated Ringer's solution into the uterine cavity via an intrauterine pressure catheter. The added fluid artificially increases amniotic fluid volume, which cushions the umbilical cord, reduces the incidence of cord compression, and decreases the need for cesarean delivery.

Step-by-Step Solution

1
Analyze the fetal heart rate tracing
Abrupt decreases in the fetal heart rate lasting 45 seconds that occur with every contraction indicate recurrent variable decelerations.
Accurate interpretation of the fetal heart rate pattern is necessary to identify the underlying pathophysiology, which in this case is umbilical cord compression.
2
Evaluate the response to initial resuscitative measures
The decelerations persist despite maternal repositioning and administration of an intravenous fluid bolus.
First-line interventions were appropriately attempted but failed to relieve the mechanical cord compression.
3
Determine the next step in the management algorithm
Select amnioinfusion to artificially replace amniotic fluid and cushion the umbilical cord.
Amnioinfusion is the standard second-line therapy for recurrent variable decelerations to prevent the need for an emergency cesarean delivery.

Key Concept

Recurrent variable decelerations unresponsive to initial resuscitative measures (repositioning, intravenous fluids) should be managed with amnioinfusion to relieve umbilical cord compression.
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Topics

Labor, Delivery, and Puerperium

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