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Question

Difficulty: HardLabor, Delivery, and Puerperium

Shortly after admission to the labor and delivery unit, a multigravid patient at 3838 weeks gestation experiences spontaneous rupture of membranes. Her prenatal records indicate an uncomplicated pregnancy, though a second-trimester anatomy scan noted a velamentous cord insertion. Immediately following the rupture of membranes, the nurse observes approximately 150 mL150\text{ mL} of bright red fluid pooling on the underpads. The external fetal monitor, which previously showed a category I tracing, now demonstrates a sudden, persistent decrease in the fetal heart rate to 75/min75/\text{min} that has lasted for 44 minutes without any sign of recovery. The patient denies any sharp abdominal pain, and her uterus is soft and non-tender between mild contractions. Maternal blood pressure is 115/75 mmHg115/75\text{ mmHg} and heart rate is 88/min88/\text{min}. Which of the following is the most appropriate initial management for this patient?

  1. Proceed immediately to cesarean deliveryAnswer
  2. B
    Initiate maternal repositioning, oxygen, and an intravenous fluid bolus
  3. C
    Perform an urgent bedside transvaginal ultrasound
  4. D
    Perform a sterile vaginal examination to place a fetal scalp electrode
  5. E
    Continue expectant management and observation

Answer

Proceed immediately to cesarean delivery
The clinical triad of a known velamentous cord insertion, painless bright red vaginal bleeding upon spontaneous membrane rupture, and a sudden, severe fetal bradycardia is highly specific for a ruptured vasa previa. In vasa previa, fetal blood vessels cross the internal cervical os without the protection of Wharton's jelly. When the membranes rupture, these vessels can tear. Because the total blood volume of a term fetus is only about 250 mL/kg250\text{ mL}/\text{kg}, loss of even a small amount of blood leads to rapid fetal exsanguination and hypovolemic shock (manifesting as profound bradycardia). The only definitive and life-saving management is an emergent cesarean delivery. Standard conservative measures are contraindicated as they waste critical time.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has painless, bright red vaginal bleeding immediately following rupture of membranes, paired with sudden, prolonged fetal bradycardia.
Identifying the nature of the bleeding and fetal heart rate changes is essential to determine the etiology.
2
Correlate the presentation with the patient's prenatal history.
The history of a velamentous cord insertion combined with the acute presentation strongly suggests ruptured vasa previa.
Vasa previa occurs when unprotected fetal vessels run through the amniotic membranes over the cervix, which are highly susceptible to tearing upon rupture of membranes.
3
Determine the appropriate management.
Because the bleeding is of fetal origin (fetal blood volume is very small), exsanguination and fetal demise occur within minutes. Immediate surgical delivery is required.
Standard conservative measures for fetal distress are insufficient when active fetal hemorrhage is occurring.

Key Concept

Ruptured vasa previa classically presents with painless vaginal bleeding and sudden fetal bradycardia immediately following rupture of membranes, requiring emergent cesarean delivery to prevent fetal exsanguination.
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Topics

Labor, Delivery, and Puerperium

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