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Difficulty: MediumObstetric Complications

A 32-year-old G2P1 woman at 35 weeks gestation is brought to the obstetric triage unit after experiencing a sudden gush of clear fluid from her vagina, followed immediately by moderate, painless vaginal bleeding. She recently immigrated and has not received regular prenatal care, missing her second-trimester anatomy ultrasound. Her temperature is 36.9°C (98.4°F), blood pressure is 112/72 mm Hg, pulse is 90/min, and respirations are 16/min. Speculum examination reveals clear fluid mixed with bright red blood pooling in the posterior vaginal fornix. The fetal heart rate tracing demonstrates a continuous, smooth, undulating baseline of 140/min with a wave frequency of 4 cycles per minute, absent short-term variability, and no accelerations or true decelerations. Which of the following is the most appropriate next step in management?

  1. A
    Transvaginal ultrasonography
  2. B
    Corticosteroid administration and continuous monitoring
  3. C
    Amnioinfusion via intrauterine pressure catheter
  4. Emergent cesarean deliveryAnswer
  5. E
    Kleihauer-Betke testing and routine observation

Answer

Emergent cesarean delivery
The correct answer is emergent cesarean delivery. This patient's presentation of a sudden gush of clear fluid (membrane rupture) followed immediately by painless vaginal bleeding is highly suspicious for ruptured vasa previa. This complication occurs when fetal blood vessels traverse the lower uterine segment over the internal cervical os, lacking the protection of Wharton's jelly or placental tissue. When the amniotic membranes rupture, these fragile vessels tear, leading to rapid fetal exsanguination. The fetal heart rate tracing confirms this catastrophic event by demonstrating a sinusoidal pattern—a smooth, continuous, undulating baseline with a frequency of 3 to 5 cycles per minute and absent variability. A sinusoidal pattern is a Category III tracing that is heavily associated with severe fetal anemia and hypoxia. Because the total blood volume of a fetus is very small, exsanguination can lead to fetal demise within minutes. Therefore, the only appropriate management is immediate surgical delivery.

Step-by-Step Solution

1
Evaluate the sequence of clinical symptoms.
The patient experienced a sudden rupture of membranes immediately followed by painless vaginal bleeding.
This specific sequence is highly suspicious for ruptured vasa previa, where fetal vessels tear along with the amniotic sac.
2
Interpret the fetal heart rate (FHR) tracing.
The FHR tracing reveals a continuous, smooth, undulating baseline with absent variability (a sinusoidal pattern).
A sinusoidal FHR pattern is a Category III tracing that is pathognomonic for severe fetal anemia and hypoxia, confirming that the vaginal blood is of fetal origin.
3
Determine the definitive management based on fetal stability.
Immediate surgical intervention is required.
Fetal exsanguination from ruptured vasa previa can lead to death within minutes, making emergent cesarean delivery the only appropriate next step.

Key Concept

Ruptured vasa previa presents with painless vaginal bleeding immediately following rupture of membranes and rapid onset of a sinusoidal fetal heart rate pattern, requiring immediate emergent cesarean delivery.
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Topics

Obstetric Complications

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