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Difficulty: HardObstetric Complications

An obstetric team is managing a multiparous patient at 36 weeks gestation who is admitted to the labor unit for induction of labor due to poorly controlled gestational diabetes. Her prenatal care was delayed, and she had only a single second-trimester ultrasound which was reportedly normal. Following artificial rupture of membranes at 5 centimeters of cervical dilation to place an internal fetal scalp electrode, the patient immediately develops moderate, bright red vaginal bleeding. Her blood pressure is 118/76 mm Hg, and pulse is 84/min. The electronic fetal monitor subsequently demonstrates a visually smooth, undulating baseline heart rate that fluctuates evenly between 130 and 150/min. This pattern repeats 4 times per minute and exhibits an absolute lack of short-term beat-to-beat variability. The fetal heart rate does not change in response to vibroacoustic stimulation. Uterine contractions remain regular every 4 minutes. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Administer an intravenous fluid bolus and reposition the patient to the left lateral decubitus position
  2. B
    Reassure the patient that these findings represent normal cervical changes and a physiologic fetal sleep cycle
  3. Perform an emergent cesarean deliveryAnswer
  4. D
    Administer intravenous terbutaline to temporarily halt uterine contractions
  5. E
    Draw maternal blood for an urgent Kleihauer-Betke test to determine the source of hemorrhage

Answer

Perform an emergent cesarean delivery
The most appropriate next step is to perform an emergent cesarean delivery. This patient's presentation is pathognomonic for a ruptured vasa previa. Vasa previa is an obstetric complication where unprotected fetal blood vessels course through the amniotic membranes directly over the internal cervical os. When the membranes were artificially ruptured (amniotomy), these fetal vessels were torn. Because the bleeding is entirely fetal in origin, the mother's vital signs remain stable. However, the fetus has a very small total blood volume, meaning even minimal bleeding causes rapid fetal exsanguination. This is confirmed by the continuous fetal monitor showing a sinusoidal pattern—a smooth, sine-wave-like baseline with absent short-term variability—which is highly indicative of severe fetal anemia and hypoxia. Fetal death is imminent, making immediate surgical delivery the only viable intervention.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient experienced moderate, bright red, painless vaginal bleeding immediately following artificial rupture of membranes. Maternal vital signs remain completely stable.
Stable maternal vitals with significant vaginal bleeding suggests the blood loss is of fetal origin, not maternal.
2
Interpret the fetal heart rate (FHR) monitor findings.
The FHR shows a smooth, undulating baseline (130-150/min) at 4 cycles per minute with absent short-term variability, which is a classic sinusoidal pattern.
A sinusoidal FHR pattern is a Category III tracing strongly associated with severe fetal anemia and hypoxia.
3
Synthesize the findings to establish a diagnosis.
The combination of immediate bleeding post-amniotomy, stable maternal vitals, and a sinusoidal FHR pattern is diagnostic of ruptured vasa previa.
Vasa previa occurs when unprotected fetal vessels run across the internal cervical os. Amniotomy tore these vessels, causing rapid fetal exsanguination (hence the sinusoidal pattern).
4
Determine the most appropriate management.
Immediate transfer to the operating room for an emergent cesarean delivery.
Because the fetal blood volume is very small (approx. 80-100 mL/kg), even a seemingly moderate hemorrhage is rapidly fatal. Emergent delivery is the only definitive, life-saving treatment.

Key Concept

Ruptured vasa previa presents with painless vaginal bleeding and rapid fetal deterioration (e.g., sinusoidal fetal heart rate pattern) immediately after membrane rupture, requiring emergent cesarean delivery.

Alternative Method

In a clinical setting without active bleeding, vasa previa is ideally diagnosed via prenatal transvaginal ultrasound using color Doppler, allowing for a planned cesarean delivery at 34-35 weeks gestation before the onset of labor or membrane rupture.
Estimated Time:1m 30s
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Topics

Obstetric Complications

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