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Difficulty: Very hardLabor, Delivery, and Puerperium

A 30-year-old gravid 2, para 1 at 40 weeks gestation is admitted to the labor and delivery unit for induction of labor due to diet-controlled gestational diabetes mellitus. Her cervix is 5 cm dilated, 90% effaced, and the fetal head is at -1 station. Over the last 30 minutes, the electronic fetal monitor has recorded an average of 7 uterine contractions per 10-minute window. The fetal heart rate baseline is 145/min with minimal variability, featuring recurrent decelerations that begin after the peak of each contraction and reach their nadir following the contraction's conclusion.

Recognizing the abnormal tracing, the clinical team immediately terminates the oxytocin infusion, repositions the patient into the left lateral decubitus position, and administers an intravenous isotonic fluid bolus. Fifteen minutes later, the physician reevaluates the patient. The uterine contraction frequency remains unchanged at 7 per 10-minute window, and the fetal heart rate continues to exhibit the same deceleration pattern. The patient's blood pressure is 118/76 mm Hg, and her pulse is 92/min. Which of the following is the most appropriate next step in management?

  1. Administer terbutalineAnswer
  2. B
    Proceed to cesarean delivery
  3. C
    Begin an isotonic amnioinfusion
  4. D
    Apply a fetal scalp electrode
  5. E
    Administer intravenous ephedrine

Answer

Administer terbutaline
The correct intervention is to administer terbutaline. The patient is experiencing uterine tachysystole (defined as more than 5 contractions in a 10-minute window) complicated by a Category II fetal heart rate tracing with recurrent late decelerations, indicating uteroplacental insufficiency. The initial management of tachysystole with an abnormal fetal heart rate pattern includes conservative intrauterine resuscitative measures: maternal repositioning, intravenous fluid administration, oxygen supplementation, and immediate cessation of any uterotonic agents (e.g., oxytocin). If uterine tachysystole and the abnormal fetal heart rate pattern persist despite these initial measures, the administration of a fast-acting tocolytic agent, such as terbutaline (a beta-2 adrenergic agonist), is the next best step. Tocolysis relaxes the uterine musculature, increasing the interval between contractions to allow for intervillous blood flow and improved fetal oxygenation. If the abnormal tracing persists despite tocolytic therapy, then prompt delivery via cesarean section is indicated.

Step-by-Step Solution

1
Identify the primary complication based on the electronic fetal monitoring data.
The tracing shows 7 contractions per 10 minutes (tachysystole) and late decelerations with minimal variability (Category II/III tracing indicating uteroplacental insufficiency).
Accurate interpretation of the fetal heart rate and contraction pattern is necessary to guide intervention.
2
Evaluate the response to initial intrauterine resuscitative measures.
Despite maternal repositioning, fluid bolus, and cessation of oxytocin, the tachysystole and late decelerations persist.
Standard initial management aims to improve uteroplacental blood flow without medication, but its failure necessitates escalating care.
3
Determine the next appropriate therapeutic intervention.
Administration of a fast-acting tocolytic agent (terbutaline) is required to relax the uterus.
Decreasing the contraction frequency will allow adequate time for placental reperfusion and improve fetal oxygenation, potentially avoiding a cesarean delivery.

Key Concept

Management of persistent uterine tachysystole with an abnormal fetal heart rate
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Topics

Labor, Delivery, and Puerperium

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