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Difficulty: HardObstetric Complications

A 24-year-old G1P0 woman at 39 weeks gestation is admitted to the labor and delivery unit in active labor. Six hours after admission, her cervix is 8 cm dilated and 100% effaced, with the fetal vertex at 0 station. Spontaneous rupture of membranes occurred 4 hours ago, yielding clear fluid. Uterine contractions are occurring every 3 to 4 minutes and are of adequate intensity. The continuous fetal heart rate monitor demonstrates a baseline of 145/min and moderate variability. However, abrupt decreases in the fetal heart rate to 80/min are noted with nearly every contraction. The onset to nadir of these decelerations takes approximately 15 seconds, and they last for 30 to 45 seconds before rapidly returning to baseline. Maternal repositioning to the left lateral decubitus position and administration of an intravenous fluid bolus are performed, but the decelerations persist. Maternal vital signs remain within normal limits. Which of the following is the most appropriate next step in management?

  1. Perform an amnioinfusionAnswer
  2. B
    Proceed to emergent cesarean delivery
  3. C
    Administer intravenous terbutaline
  4. D
    Reassurance and continued routine monitoring
  5. E
    Attempt operative vaginal delivery with vacuum extraction

Answer

The most appropriate next step in management is to perform an amnioinfusion.
The correct action is an amnioinfusion because the patient presents with recurrent variable decelerations (abrupt onset to nadir) that have not resolved with initial conservative measures like maternal repositioning and intravenous fluids. Since the fetal heart rate tracing maintains moderate variability (Category II), immediate surgical delivery is not required. Amnioinfusion involves instilling isotonic fluid into the uterine cavity, which helps relieve the umbilical cord compression underlying the decelerations, particularly in the setting of ruptured membranes.

Step-by-Step Solution

1
Interpret the continuous fetal heart rate tracing.
The FHR shows a normal baseline (145/min) and moderate variability, but with abrupt decelerations (onset to nadir <30 seconds) occurring with contractions.
Identifying the deceleration type precisely distinguishes variable decelerations (abrupt) from late decelerations (gradual).
2
Identify the underlying pathophysiology of the FHR abnormality.
Recurrent variable decelerations are recognized as a sign of umbilical cord compression, which is common following rupture of membranes.
Understanding the etiology guides targeted therapy to relieve the compression.
3
Evaluate the clinical response to initial resuscitative measures.
Initial interventions (maternal repositioning and intravenous fluid bolus) were ineffective in resolving the decelerations.
Failure of first-line measures dictates progression to the next step in the clinical management algorithm.
4
Select the definitive next step for unresolved recurrent variable decelerations in a Category II tracing.
Amnioinfusion is chosen to artificially restore amniotic fluid volume and decompress the umbilical cord.
This is the standard of care to relieve cord compression before considering a cesarean delivery, provided the FHR tracing remains Category II.

Key Concept

Management of recurrent variable decelerations in labor involves sequential intrauterine resuscitation; if initial measures like maternal repositioning and IV fluids fail, an amnioinfusion is indicated to relieve umbilical cord compression.
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Topics

Obstetric Complications

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