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Difficulty: Very hardObstetric Complications

A 26-year-old primigravid patient at 40 weeks gestation is admitted to the labor and delivery unit in active spontaneous labor. Her prenatal course was uncomplicated. Spontaneous rupture of membranes occurred 4 hours ago, revealing thick meconium-stained amniotic fluid. Her temperature is 37.1°C (98.8°F), blood pressure is 118/76 mmHg, and pulse is 82/min.

Pelvic examination demonstrates the cervix is 6 cm dilated, 100% effaced, and the fetal vertex is at 0 station. No structures are palpable ahead of the presenting part.

Continuous external fetal monitoring over the last 30 minutes shows a baseline heart rate of 140/min and moderate variability. There are recurrent, abrupt decreases in the fetal heart rate to 80/min that last for 45 to 60 seconds before returning rapidly to baseline. These decreases do not have a consistent temporal relationship with the uterine contractions. The contractions are occurring every 3 to 4 minutes and last 60 seconds.

The nurse assists the patient into the left lateral, right lateral, and hands-and-knees positions, and administers a 500 mL intravenous bolus of lactated Ringer solution. Despite these resuscitative maneuvers, the fetal heart rate pattern remains unchanged for the next 20 minutes. A repeat cervical examination shows no change in dilation.

Which of the following is the most appropriate next step in management?

  1. Transcervical amnioinfusion to relieve umbilical cord compressionAnswer
  2. B
    Transcervical amnioinfusion to dilute the meconium-stained amniotic fluid
  3. C
    Immediate preparation for an emergent cesarean delivery
  4. D
    Administration of subcutaneous terbutaline
  5. E
    Placement of a fetal scalp electrode for internal monitoring

Answer

The most appropriate next step is to perform a transcervical amnioinfusion to relieve umbilical cord compression.
The patient's fetal heart rate monitoring demonstrates recurrent variable decelerations, characterized by an abrupt decrease in the heart rate (onset to nadir in less than 30 seconds) that is visually unassociated with uterine contractions. Variable decelerations are caused by umbilical cord compression, which can be exacerbated by the loss of amniotic fluid following rupture of membranes. Initial management of recurrent variable decelerations includes maternal repositioning (to shift the fetus off the cord) and intravenous fluid hydration. When these initial resuscitative measures fail to resolve the decelerations, transcervical amnioinfusion (instillation of normal saline or lactated Ringer solution into the uterine cavity) is the next indicated step. Amnioinfusion artificially restores the amniotic fluid volume, providing a protective cushion around the umbilical cord and relieving the compression.

Step-by-Step Solution

1
Analyze the fetal heart rate (FHR) tracing characteristics.
The FHR shows recurrent, abrupt decelerations that vary in timing relative to contractions, identifying them as variable decelerations.
Accurate identification of the deceleration type is essential to determine the underlying pathophysiology.
2
Determine the pathophysiology of the decelerations.
Variable decelerations are caused by umbilical cord compression, which is likely exacerbated in this patient by the spontaneous rupture of membranes and subsequent loss of amniotic fluid.
Understanding the cause directs the specific resuscitative intervention.
3
Evaluate the response to initial resuscitative measures.
Maternal repositioning and intravenous fluids failed to resolve the variable decelerations.
If initial measures fail, secondary interventions are required to prevent fetal acidemia.
4
Select the definitive secondary intervention.
Transcervical amnioinfusion is selected to artificially replace the lost amniotic fluid and cushion the umbilical cord.
Amnioinfusion directly addresses the pathophysiology of cord compression when positional changes are inadequate.

Key Concept

Recurrent variable decelerations are caused by umbilical cord compression and are managed with maternal repositioning followed by transcervical amnioinfusion if initial measures fail. Amnioinfusion is no longer indicated for the prophylactic dilution of meconium.
Estimated Time:1m 30s
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Topics

Obstetric Complications

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