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A 33-year-old primigravid presents for an evaluation after a first-trimester ultrasound. She was told that she was carrying twins, but they were joined at the belly and chest. She also complains of increased distress and anxiety since her first appointment.
She wants to know more about the twins being joined. If an ultrasonographic scan is done, what can be observed that differentiates this dyad from dorsally conjoined twins?
Choices:
1. They are monochorionic and monoamniotic.
2. They have two separate umbilical cords.
3. They almost always have separate organs.
4. They have a single shared umbilical cord.
Answer: 4 -They have a single shared umbilical cord.
Explanations:
• Conjoined twins can be broadly categorized into non-dorsally conjoined twins, including ventral, lateral, and caudal conjunction, and dorsally conjoined twins. Non-dorsal conjunction may have a varied presentation but has a single umbilical cord shared between the twins.
• It is proposed that non-dorsal conjunction may be initiated by initial duplication of axial primordia, which leads to change in the axial orientation and interaction aplasia.
• Non-Dorsal conjunction is more likely to share vital organs than dorsal conjunction.
•Dorsal conjunction may occur because of secondary fusion of initially separate monozygotic twins. Dorsal conjunction presents with two umbilical cords and mostly separate internal organs.
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