A woman in labour with a twin pregnancy is being monitored. The first twin shows a low fetal heart rate. Suddenly the second twin's heart sounds become absent and the mother develops a weak, thready pulse and signs of shock. What is the most likely diagnosis?

1. A

   Uterine rupture

2. B

   Cord prolapse of the second twin

3. C

   Abruptio placentae (placental abruption)

4. D

   Vasa previa

Appeared in: NORCET 9 Prelims-2025

Explanation

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• Uterine rupture is a full-thickness tear of the uterine wall, which is a rare but life-threatening event.
• In this scenario, the twin pregnancy leads to uterine overdistension, a primary risk factor that weakens the uterine muscle.
• The rupture causes massive internal hemorrhage, leading to sudden hypovolemic shock in the mother (weak, thready pulse).
• Simultaneously, the rupture disrupts placental perfusion or leads to fetal expulsion into the abdomen, causing acute fetal hypoxia and the abrupt loss of heart sounds.
• The combination of a known risk factor (twins) with the sudden, simultaneous collapse of both mother and fetus makes uterine rupture the most fitting diagnosis.

Why Other Options Were Wrong

• Option B: Cord prolapse affects only the fetus by compressing the umbilical cord, leading to fetal distress or demise. It does not cause maternal hemorrhage or shock.
• Option C: While abruptio placentae can cause both maternal shock and fetal distress, the presentation in the context of a severely overdistended (twin) uterus makes rupture a more specific diagnosis for such a sudden and catastrophic collapse. The clinical signs of rupture and abruption can be very similar.
• Option D: Vasa previa involves the tearing of fetal blood vessels. The resulting hemorrhage is purely fetal blood. This causes rapid fetal demise but does not affect the mother's circulatory volume or lead to maternal shock.

Related Visual

Clinical Relevance

• Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Recognition and differentiation of life-threatening obstetric emergencies during labor in acute care settings.
• Recognizing the signs of uterine rupture is a critical nursing skill, as immediate intervention is required to save the lives of both the mother and fetus.
• The nurse's primary role is rapid assessment, initiating maternal resuscitation (ABCs - Airway, Breathing, Circulation), activating the emergency response team, and preparing for immediate surgery.
• Patient safety depends on high suspicion in at-risk patients (e.g., twin gestation, prior C-section) and not dismissing sudden changes in maternal or fetal status.

How to Approach the Question

• First, identify the key elements of the clinical scenario: a high-risk pregnancy (twins), an intrapartum setting, and a sudden, severe change in status.
• Separate the maternal signs (weak, thready pulse, shock) from the fetal signs (absent heart sounds of the second twin).
• Analyze the options based on whether they can explain BOTH the maternal and fetal signs simultaneously.
• Rule out options that only explain one part of the clinical picture. Cord prolapse and vasa previa explain fetal demise but not maternal shock.
• Differentiate between the remaining options (uterine rupture and abruptio placentae). Consider the risk factors. The overdistended uterus from a twin pregnancy is a classic risk factor for rupture.
• Conclude that the catastrophic, simultaneous collapse of both mother and fetus in this high-risk setting is most characteristic of uterine rupture.

Concept Tested & Keywords

• Concept Tested: Recognition and differentiation of life-threatening obstetric emergencies during labor.
• Stem keywords: twin pregnancy, labour, absent heart sounds, maternal shock, weak, thready pulse
• Lead-in keywords: most likely diagnosis
• Clinical cues: The presence of a twin pregnancy indicates uterine overdistension, a significant risk factor for uterine rupture.
• Clinical cues: The simultaneous and sudden onset of severe maternal shock and fetal demise is the classic presentation of a catastrophic uterine rupture.

Question ID

QReYSXt25Mj9sWqMbCdGZL

Copy ID

Reference Book

E6 Obstetrics Williams p. 72-94

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 1049-1051