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Difficulty: MediumLabor, Delivery, and Puerperium

A 24-year-old primigravida at 40 weeks and 3 days gestation is evaluated in the labor and delivery ward. She was admitted in spontaneous active labor 8 hours ago. Her temperature is 37.1°C (98.8°F), blood pressure is 118/74 mm Hg, and pulse is 82/min. The estimated fetal weight is 3300 g. A cervical examination shows 8 cm dilation, 100% effacement, and +1 station. Artificial rupture of membranes was performed 4 hours ago and revealed clear fluid. Uterine contractions are occurring every 2 to 3 minutes. Continuous fetal monitoring demonstrates a baseline heart rate of 145/min with moderate variability. During the last 45 minutes, the fetal heart rate has repeatedly shown abrupt decreases to 85/min that last for 40 to 60 seconds and occur with most contractions. The patient has been repositioned to the left lateral decubitus position, and an intravenous fluid bolus has been completed, but the decelerations persist. Which of the following is the most appropriate next step in management?

  1. AmnioinfusionAnswer
  2. B
    Cesarean delivery
  3. C
    Intravenous terbutaline
  4. D
    Observation with continuous monitoring
  5. E
    Vacuum-assisted vaginal delivery

Answer

Amnioinfusion
The patient's fetal monitoring shows recurrent variable decelerations (abrupt decreases in fetal heart rate lasting less than 2 minutes) with moderate baseline variability. Variable decelerations are characteristically caused by umbilical cord compression. When initial conservative measures, such as maternal repositioning (to relieve occult cord compression) and intravenous fluid boluses, fail to resolve recurrent variable decelerations, amnioinfusion is the most appropriate next step. Amnioinfusion involves instilling isotonic fluid into the uterine cavity through an intrauterine pressure catheter. This artificially replaces the amniotic fluid volume, effectively cushioning the umbilical cord, reducing compression during contractions, and often avoiding the need for an emergent Cesarean delivery.

Step-by-Step Solution

1
Interpret the fetal heart rate tracing.
The tracing shows a baseline of 145/min with moderate variability and abrupt decreases to 85/min lasting 40-60 seconds with contractions.
These findings are diagnostic of recurrent variable decelerations, which indicate umbilical cord compression.
2
Assess the response to initial interventions.
Maternal repositioning and an intravenous fluid bolus have already been attempted but failed to resolve the decelerations.
This establishes that first-line conservative intrauterine resuscitation measures have been exhausted and a more targeted intervention is required.
3
Determine the definitive next step for unresolved recurrent variable decelerations.
Amnioinfusion is the preferred intervention.
Instilling saline into the uterine cavity restores fluid volume, cushioning the umbilical cord to relieve compression while allowing labor to safely continue.

Key Concept

Recurrent variable decelerations indicate umbilical cord compression. When initial measures like maternal repositioning fail, amnioinfusion is the next best step to alleviate compression and prevent the need for Cesarean delivery.
Estimated Time:1m 15s
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Topics

Labor, Delivery, and Puerperium

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