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Difficulty: MediumObstetric Complications

A primigravid patient at 39 weeks and 5 days of gestation is admitted to the labor and delivery ward in active labor. She has no significant past medical history and her prenatal course was unremarkable. Pelvic examination reveals a cervix that is 7 cm dilated and 100% effaced, with the fetal vertex at 0 station. Clear amniotic fluid is noted following spontaneous membrane rupture three hours ago. Uterine contractions are occurring every 3 minutes. The continuous fetal heart rate monitor shows a baseline of 145/min with moderate variability. During the last 40 minutes, there are recurrent, abrupt decreases in the fetal heart rate to 85/min that last for approximately 45 seconds. The onset, depth, and duration of these decelerations vary from one contraction to the next, often without a consistent relationship to the peak of the contraction. Initial resuscitative measures, including maternal repositioning to the left lateral decubitus position and administration of an intravenous fluid bolus, have been performed. Despite these interventions, the fetal heart rate pattern remains unchanged. Which of the following is the most appropriate next step in management?

  1. A
    Proceed immediately to cesarean delivery
  2. B
    Administer intravenous terbutaline
  3. Initiate a transcervical amnioinfusionAnswer
  4. D
    Reassure the patient and continue routine observation
  5. E
    Administer intravenous oxytocin

Answer

The most appropriate next step is to initiate a transcervical amnioinfusion.
The patient's fetal heart rate tracing demonstrates recurrent variable decelerations, characterized by abrupt decreases in heart rate that vary in timing relative to uterine contractions. These are primarily caused by umbilical cord compression, which is common following the rupture of membranes. When initial intrauterine resuscitative measures (such as maternal repositioning and intravenous fluid boluses) fail to resolve recurrent variable decelerations, the next most appropriate step is a transcervical amnioinfusion. This procedure involves instilling isotonic fluid into the amniotic cavity to artificially restore amniotic fluid volume, thereby cushioning the umbilical cord, relieving compression, and decreasing the need for operative delivery.

Step-by-Step Solution

1
Interpret the fetal heart rate tracing.
The tracing demonstrates recurrent variable decelerations.
The abrupt decreases in heart rate (onset to nadir <30 seconds) that vary in timing relative to uterine contractions define variable decelerations.
2
Determine the underlying etiology.
Umbilical cord compression.
Variable decelerations are classically caused by compression of the umbilical cord, which frequently occurs after rupture of membranes due to the loss of protective amniotic fluid.
3
Evaluate the response to initial resuscitative measures.
The decelerations persisted despite maternal repositioning and IV fluids.
Initial conservative management failed to successfully relieve the cord compression.
4
Select the definitive next best step in management.
Transcervical amnioinfusion.
Instillation of fluid into the uterine cavity artificially restores the amniotic fluid volume, providing a cushion for the umbilical cord and thereby resolving the decelerations and potentially avoiding a cesarean delivery.

Key Concept

Management of recurrent variable decelerations with amnioinfusion
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Topics

Obstetric Complications

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