A primigravid patient at 40 weeks and 3 days of gestation is admitted to the labor and del… — USMLE Step 2 CK

A primigravid patient at $40$ weeks and $3$ days of gestation is admitted to the labor and delivery unit for an elective induction of labor. An induction is currently underway using a continuous intravenous oxytocin infusion. Her epidural analgesia is functioning well and providing adequate pain relief. Her vital signs are within normal limits, with a blood pressure of $118/74$ mm Hg, a heart rate of $82$ /min, and a temperature of $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ). Routine admission laboratory studies reveal a hemoglobin of $10.5$ g/dL and a platelet count of $165,000/\text{mm}^3$ . A recent pelvic examination demonstrates cervical dilation of $6$ cm and effacement of $100\%$ , with the fetal vertex at $0$ station. External tocodynamometry records uterine contractions occurring every $2$ to $3$ minutes. Cardiotocography displays a baseline fetal heart rate of $128$ /min accompanied by minimal variability. The tracing also shows gradual, symmetric drops in the fetal heart rate to a nadir of $115$ /min. The onset of each drop consistently begins after the peak of the associated contraction, and the heart rate returns to baseline only after the uterine tone has normalized. These episodes occur with nearly every contraction. Which of the following is the most appropriate next step in management?

Halt the intravenous oxytocin infusionAnswer
B
Prepare the patient for an urgent cesarean delivery
C
Infuse warmed saline via a transcervical intrauterine pressure catheter
D
Maintain current observation as this is a benign finding
E
Administer a transfusion of packed red blood cells

Answer

Halt the intravenous oxytocin infusion

The patient's fetal heart rate tracing reveals recurrent late decelerations (decreases that begin after the contraction's peak) accompanied by minimal variability. This is a concerning pattern indicative of uteroplacental insufficiency and transient fetal hypoxia. The most appropriate immediate step is to initiate intrauterine resuscitation to restore adequate placental perfusion. Halting the intravenous oxytocin infusion is a critical first-line intervention because it decreases contraction frequency and intensity, allowing the uteroplacental blood flow time to recover. Additional concurrent resuscitative steps typically include repositioning the mother into a lateral decubitus position, administering an intravenous fluid bolus, and providing supplemental oxygen.

Step-by-Step Solution

Interpret the cardiotocography (CTG) tracing.

The tracing demonstrates a baseline of 128/min with minimal variability and recurrent late decelerations (symmetric drops beginning after the contraction peak).

Accurate interpretation of the fetal heart rate is required to identify the presence and type of fetal distress.

Diagnose the underlying etiology of the fetal heart rate abnormalities.

Recurrent late decelerations are a hallmark of uteroplacental insufficiency, which leads to transient fetal hypoxia.

Understanding that the placenta is failing to provide adequate oxygen during contractions dictates the required therapeutic approach.

Select the most appropriate initial medical intervention.

The primary goal is to improve uteroplacental blood flow by reducing uterine work; this is achieved by immediately stopping the oxytocin infusion.

Before invasive procedures (like cesarean delivery) are considered, first-line intrauterine resuscitation measures must be deployed.

Key Concept

Intrauterine resuscitation for recurrent late decelerations

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