A 35-year-old woman, gravida 2, para 1, at 41 weeks gestation is admitted to the labor and… — USMLE Step 2 CK

A $35$ -year-old woman, gravida $2$ , para $1$ , at $41$ weeks gestation is admitted to the labor and delivery unit for induction of labor due to a post-term pregnancy. An intravenous oxytocin infusion is started. Six hours later, her cervix is $5\text{ cm}$ dilated and $90\%$ effaced, with the fetal vertex at $-1$ station. Uterine contractions are occurring every $4\text{ minutes}$ and are of moderate intensity. Her temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $120/75\text{ mmHg}$ , and pulse is $88\text{/min}$ . Laboratory studies from admission show a hemoglobin of $10.6\text{ g/dL}$ and a platelet count of $210,000\text{/mm}^3$ . The fetal heart rate monitoring demonstrates a baseline of $135\text{/min}$ with minimal variability. Over the past $20\text{ minutes}$ , the tracing reveals recurrent, gradual decreases in the fetal heart rate that begin after the peak of each contraction and take approximately $40\text{ seconds}$ to reach their nadir. The fetal heart rate returns to baseline only after the contraction has fully ended. Which of the following is the most appropriate next step in management?

A
Immediate emergency cesarean delivery
B
Maintain oxytocin infusion and apply a fetal scalp electrode
C
Transfusion of packed red blood cells
Discontinue oxytocin infusion and reposition the patient laterallyAnswer
E
Transcervical amnioinfusion

Answer

Discontinue oxytocin infusion and reposition the patient laterally.

The patient's fetal heart rate tracing demonstrates late decelerations (a gradual decrease in heart rate beginning after the contraction peak), which are a hallmark sign of uteroplacental insufficiency. The first-line management for this Category II tracing is intrauterine resuscitation. This involves discontinuing uterotonic agents (such as oxytocin) to reduce uterine activity and maternal repositioning (typically to the left lateral decubitus position) to relieve aortocaval compression and maximize uterine blood flow. Additional resuscitative measures can include an intravenous fluid bolus and the administration of supplemental oxygen.

Step-by-Step Solution

Analyze the fetal heart rate (FHR) tracing described in the stem.

The tracing shows recurrent decelerations with a gradual onset that begin after the peak of the contraction and return to baseline after the contraction ends.

Identifying the specific type of FHR deceleration is required to determine the underlying etiology and guide management.

Correlate the FHR pattern with its pathophysiology.

The pattern describes late decelerations, which are indicative of uteroplacental insufficiency.

Late decelerations reflect transient fetal hypoxemia during uterine contractions due to compromised placental perfusion, which is commonly seen in post-term pregnancies.

Determine the initial management for late decelerations in a patient receiving oxytocin.

The most appropriate next step is intrauterine resuscitation, starting with discontinuing the oxytocin infusion and repositioning the patient laterally.

Discontinuing oxytocin reduces uterine activity, thereby improving placental blood flow. Lateral maternal repositioning relieves aortocaval compression, further optimizing cardiac output and uterine perfusion.

Key Concept

Recurrent late decelerations indicate uteroplacental insufficiency and should initially be managed with intrauterine resuscitation, which includes discontinuing uterotonics (like oxytocin), lateral maternal repositioning, an intravenous fluid bolus, and supplemental oxygen.

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