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Difficulty: HardLabor, Delivery, and Puerperium

A 26-year-old G1P0 woman at 39 weeks gestation is evaluated in the labor and delivery unit for active labor. Her pregnancy has been uncomplicated. Her membranes spontaneously ruptured 4 hours ago, yielding clear fluid. Her temperature is 37.1°C (98.8°F), blood pressure is 120/78 mm Hg, and pulse is 88/min. Laboratory studies show a hemoglobin concentration of 10.5 g/dL. The cervix is 7 cm dilated, 100% effaced, and the fetal vertex is at 0 station. Uterine contractions occur every 3 minutes and are of moderate intensity. Fetal heart rate monitoring demonstrates a baseline of 140/min with moderate variability. Over the last 45 minutes, there are recurrent, abrupt decreases in the fetal heart rate to 80-90/min, lasting for 45-60 seconds, which occur with approximately 60% of the contractions. The decelerations rapidly return to the baseline. Maternal repositioning to the left lateral decubitus position, administration of oxygen, and an intravenous fluid bolus are performed, but the fetal heart rate pattern remains unchanged over the next 15 minutes. Which of the following is the most appropriate next step in management?

  1. AmnioinfusionAnswer
  2. B
    Cesarean delivery
  3. C
    Vacuum-assisted vaginal delivery
  4. D
    Administration of terbutaline
  5. E
    Transfusion of packed red blood cells

Answer

Amnioinfusion
The correct answer is amnioinfusion. This patient's fetal heart rate monitoring demonstrates recurrent variable decelerations, which are defined as abrupt decreases in the fetal heart rate (onset to nadir in less than 30 seconds) that drop at least 15 beats per minute below baseline for at least 15 seconds. They are caused by umbilical cord compression, which is particularly common after the rupture of membranes (as seen in this patient) due to the loss of amniotic fluid cushioning. Initial management of recurrent variable decelerations involves noninvasive intrauterine resuscitation, including maternal repositioning, intravenous fluid administration, and supplemental oxygen. If the decelerations persist despite these initial measures, the next appropriate step is an amnioinfusion. This procedure involves instilling an isotonic fluid (such as normal saline) through an intrauterine pressure catheter into the amniotic cavity. The added fluid restores the amniotic cushion, relieves the compression on the umbilical cord, and often resolves the decelerations, potentially avoiding an unnecessary surgical delivery.

Step-by-Step Solution

1
Analyze the fetal heart rate (FHR) description.
The FHR shows abrupt decreases to 80-90/min that quickly return to baseline.
Abrupt decreases in FHR characterize variable decelerations, which are typically caused by umbilical cord compression.
2
Evaluate the current management status.
Initial intrauterine resuscitation (maternal repositioning, oxygen, IV fluids) has already been performed without success.
Variable decelerations are first managed with noninvasive maneuvers. If these fail, escalated intervention is required.
3
Determine the next best step for refractory variable decelerations.
Amnioinfusion is indicated.
Instilling saline into the amniotic cavity relieves umbilical cord compression and often resolves variable decelerations, potentially averting the need for a cesarean delivery.

Key Concept

Recurrent variable decelerations are caused by umbilical cord compression. If initial intrauterine resuscitation measures fail, the next step in management is amnioinfusion.
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Topics

Labor, Delivery, and Puerperium

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