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Difficulty: HardObstetric Complications

Following the spontaneous onset of regular contractions, a multiparous patient at 38 weeks gestation is admitted to the delivery unit. She is 31 years old (gravida 2, para 1). Her prenatal history is significant for a mid-trimester anatomy ultrasound demonstrating a low-lying placenta; however, a follow-up transvaginal ultrasound at 32 weeks confirmed that the placental edge had migrated 4 cm away from the internal cervical os. Her vital signs upon admission are temperature 37.0°C (98.6°F), blood pressure 118/76 mm Hg, and heart rate 84/min.

Cervical examination demonstrates 6 cm dilation, 100% effacement, and 0 station with a tense, bulging amniotic sac. The baseline fetal heart rate is 140/min with moderate variability and no decelerations. Ten minutes later, the patient's membranes spontaneously rupture. Immediately following the rupture, a large gush of blood-tinged fluid is observed, rapidly followed by frank, bright red vaginal bleeding. The patient's uterine tone remains soft between contractions, and she explicitly denies any new, sudden, or tearing abdominal pain. Simultaneous evaluation of the fetal monitor reveals a precipitous drop in the fetal heart rate to 60/min. Three minutes later, the bradycardia persists without any sign of recovery.

Which of the following is the most appropriate next step in management?

  1. Emergent cesarean deliveryAnswer
  2. B
    Maternal repositioning, oxygen administration, and intravenous fluid bolus
  3. C
    Bedside transabdominal ultrasound
  4. D
    Placement of an intrauterine pressure catheter and amnioinfusion
  5. E
    Reassurance and continued expectant management

Answer

Emergent cesarean delivery is the most appropriate next step due to the high suspicion for a ruptured vasa previa causing rapid fetal exsanguination.
The correct response is emergent cesarean delivery. This patient is exhibiting the pathognomonic triad of a ruptured vasa previa: rupture of membranes, followed by painless vaginal bleeding, and culminating in rapid fetal deterioration (prolonged bradycardia or sinusoidal pattern). Her history of a resolved low-lying placenta is a classic risk factor; as the bulk of the placenta migrates toward the fundus, it can leave behind membranous fetal vessels spanning the cervical os. When the membranes spontaneously ruptured, these unprotected fetal vessels were torn. Because the bleeding is fetal in origin, even a small volume of visible blood represents a massive, life-threatening hemorrhage for the fetus. Immediate surgical delivery is the only intervention that can prevent fetal demise.

Step-by-Step Solution

1
Identify the classic clinical triad presented in the vignette.
The patient experiences spontaneous rupture of membranes, immediately followed by painless frank vaginal bleeding and a sudden, prolonged fetal bradycardia.
Recognizing this triad is critical for distinguishing vasa previa rupture from other causes of intrapartum bleeding.
2
Correlate the acute presentation with the patient's prenatal history.
The patient had a low-lying placenta that 'resolved' by 32 weeks.
As a low-lying placenta migrates upward with the growing uterus, it can leave behind aberrant, unprotected fetal vessels (vasa previa) traversing the fetal membranes over the internal cervical os.
3
Differentiate the etiology from other obstetric emergencies.
The absence of sudden, tearing abdominal pain and the presence of a soft uterus between contractions make placental abruption or uterine rupture highly unlikely.
The bleeding is entirely fetal in origin. Because the total fetal blood volume is small (approximately 250-300 mL at term), rupture of these vessels leads to rapid fetal exsanguination and sudden bradycardia.
4
Determine the definitive management.
The fetus is actively exsanguinating and exhibiting a terminal heart rate pattern.
Immediate emergent cesarean delivery is required to prevent fetal demise. Any delay for diagnostic testing or conservative measures will result in fetal death.

Key Concept

Vasa Previa Rupture and Intrapartum Management
Estimated Time:2m 0s
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Topics

Obstetric Complications

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