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Difficulty: MediumObstetric Complications

A 29-year-old woman, gravida 1, para 0, at 40 weeks gestation is admitted to the labor and delivery unit in spontaneous labor. Her pregnancy has been uncomplicated. Four hours after admission, her cervical examination reveals 6 cm dilation, 90% effacement, and -1 station. She is currently receiving an intravenous oxytocin infusion for labor augmentation due to inadequate cervical progression. Her temperature is 37.1°C (98.8°F), blood pressure is 120/78 mm Hg, and pulse is 88/min. Continuous fetal monitoring shows a baseline heart rate of 145/min with moderate variability. Over the last 30 minutes, there is an average of 7 contractions in a 10-minute window. The fetal heart rate tracing demonstrates symmetric, gradual decreases in the fetal heart rate that begin after the peak of the contraction and return to baseline after the contraction ends. These decelerations are occurring with nearly every contraction. Which of the following is the most appropriate next step in management?

  1. Discontinue the intravenous oxytocinAnswer
  2. B
    Prepare for an emergent cesarean delivery
  3. C
    Administer a transcervical amnioinfusion
  4. D
    Continue current management and observe closely
  5. E
    Administer intravenous terbutaline

Answer

Discontinue the intravenous oxytocin
The correct intervention is to discontinue the intravenous oxytocin. The patient's presentation of 7 contractions in a 10-minute window indicates uterine tachysystole. The associated gradual decreases in fetal heart rate that begin after the contraction peak are late decelerations, which occur due to uteroplacental insufficiency. The excessive frequency of contractions restricts blood flow to the intervillous space, causing transient fetal hypoxemia. The initial step in intrauterine resuscitation for tachysystole is to discontinue any uterotonic agents. Other immediate measures include maternal repositioning (left lateral decubitus), administering an intravenous fluid bolus, and providing supplemental oxygen.

Step-by-Step Solution

1
Analyze the contraction pattern described in the fetal heart rate tracing.
The tracing shows 7 contractions in a 10-minute window, which meets the definition for uterine tachysystole (abnormally frequent contractions, defined as >5 contractions in 10 minutes averaged over 30 minutes).
Identifying abnormal uterine activity is crucial because it can compromise blood flow to the intervillous space.
2
Interpret the type of fetal heart rate decelerations occurring.
The decelerations are described as symmetric and gradual, beginning after the peak of the contraction and returning to baseline after the contraction ends. This is the classic description of late decelerations.
Late decelerations signify uteroplacental insufficiency and transient fetal hypoxemia.
3
Synthesize the findings to determine the next best step in management.
The patient has uteroplacental insufficiency driven by oxytocin-induced uterine tachysystole. The immediate intervention required is intrauterine resuscitation by discontinuing the oxytocin infusion.
Stopping the uterotonic agent is the most direct way to reduce contraction frequency, thereby restoring placental perfusion and improving fetal oxygenation.

Key Concept

The initial management of recurrent late decelerations caused by oxytocin-induced uterine tachysystole is discontinuation of the oxytocin infusion.
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Topics

Obstetric Complications

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