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Difficulty: HardObstetric Complications

A 31-year-old woman, gravida 3, para 2, at 35 weeks and 2 days of gestation presents to the obstetrical triage unit reporting a sudden gush of clear vaginal fluid that occurred 30 minutes ago. Shortly after her arrival, she experiences another gush of fluid, this time mixed with a moderate amount of bright red blood. The patient reports no uterine contractions or abdominal pain. Her temperature is 37.1°C (98.8°F), blood pressure is 112/72 mm Hg, and pulse is 88/min. Physical examination reveals a soft, non-tender uterus. A prenatal ultrasound at 20 weeks revealed an anterior placenta with a succenturiate lobe in the lower uterine segment. Continuous electronic fetal monitoring shows a baseline heart rate of 140/min that rapidly deteriorates into a smooth, undulating pattern with a frequency of 3 to 5 cycles per minute and absent variability. Which of the following is the most appropriate next step in the management of this patient?

  1. Proceed to emergent cesarean deliveryAnswer
  2. B
    Initiate a transcervical amnioinfusion
  3. C
    Administer intravenous magnesium sulfate and intramuscular betamethasone
  4. D
    Perform a sterile digital cervical examination
  5. E
    Obtain maternal blood for a Kleihauer-Betke test

Answer

Proceed to emergent cesarean delivery
The patient's clinical presentation of painless vaginal bleeding immediately following rupture of membranes, combined with a succenturiate placental lobe and a sinusoidal fetal heart rate pattern, is highly indicative of ruptured vasa previa. Vasa previa occurs when fetal blood vessels run through the amniotic membranes directly over the internal cervical os. When the membranes rupture, these unprotected vessels can easily tear, leading to rapid fetal exsanguination. The smooth, undulating fetal heart rate pattern described (sinusoidal pattern) is a classic Category III tracing that signifies severe fetal anemia and hypoxia. Because total fetal blood volume is very small, exsanguination occurs rapidly. The only definitive and life-saving management is immediate emergent cesarean delivery.

Step-by-Step Solution

1
Analyze the maternal presentation and risk factors.
The patient has painless vaginal bleeding immediately following rupture of membranes, with a known ultrasound history of a succenturiate placental lobe.
A succenturiate lobe often involves fetal vessels traveling through the membranes unprotected by Wharton jelly or placental tissue, which defines vasa previa.
2
Interpret the fetal heart rate (FHR) tracing.
The FHR shows a smooth, undulating pattern at 3 to 5 cycles per minute with absent variability.
This describes a sinusoidal FHR pattern, which is a Category III tracing strongly associated with severe fetal anemia, hypoxia, and acute exsanguination.
3
Determine the definitive next best step in management.
Emergent cesarean delivery must be performed immediately.
Rupture of vasa previa causes rapid fetal blood loss. Because fetal blood volume is extremely small, any delay for further testing or conservative management will result in fetal death.

Key Concept

Vasa Previa Rupture and Sinusoidal Fetal Heart Rate Pattern
Estimated Time:1m 30s
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Topics

Obstetric Complications

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