Question:hard
Confined blood chimerism is associated with which of the following?
Confined blood chimerism is associated with which of the following?
Show Hint
Blood swap needs vascular anastomoses, which exist only in a shared monochorionic placenta.
Updated On: Jun 24, 2026
- Dichorionic diamniotic twins
- Monochorionic diamniotic twins
- Singleton pregnancy
- Monochorionic monoamniotic twins
Show Solution
The Correct Option is B
Solution and Explanation
Work from the mechanism. Chimerism means one body carrying two genetically different cell lines. When this is restricted to the bloodstream it is called confined (or hematopoietic) blood chimerism, and it appears when twins swap blood cells before birth.
For blood to pass from one twin to another there must be a physical plumbing link between their circulations. That link only exists when the twins share one placenta, that is, a monochorionic placenta, where vascular anastomoses connect the two fetal circulations. Twins with two separate placentas (dichorionic) have no such bridges, so cells cannot cross and chimerism does not develop. A singleton has no partner at all.
The word confined signals that the donated cells settle only in the hematopoietic compartment rather than seeding every tissue, consistent with an exchange through shared placental vessels. Of the listed options, the monochorionic diamniotic twin pair is the classic monochorionic arrangement that carries these anastomoses and is the keyed association for confined blood chimerism.
So shared-placenta twins, specifically monochorionic diamniotic, are the answer.
\[\boxed{\text{Monochorionic diamniotic twins}}\]
For blood to pass from one twin to another there must be a physical plumbing link between their circulations. That link only exists when the twins share one placenta, that is, a monochorionic placenta, where vascular anastomoses connect the two fetal circulations. Twins with two separate placentas (dichorionic) have no such bridges, so cells cannot cross and chimerism does not develop. A singleton has no partner at all.
The word confined signals that the donated cells settle only in the hematopoietic compartment rather than seeding every tissue, consistent with an exchange through shared placental vessels. Of the listed options, the monochorionic diamniotic twin pair is the classic monochorionic arrangement that carries these anastomoses and is the keyed association for confined blood chimerism.
So shared-placenta twins, specifically monochorionic diamniotic, are the answer.
\[\boxed{\text{Monochorionic diamniotic twins}}\]
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