This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Blood chimerism is most likely to occur in which of the following? 
Select and explain. 
A. Monochorionic Monozygotic twins, B. Monochorionic Dizygotic twins, C. Dichorionic Dizygotic twins, D. Singleton pregnancy
B: Monochorionic Dizygotic twins
Answer: B: Monochorionic Dizygotic twins 
Explanation: Chimerism refers to the amount each cord blood or the recipient contributes to hematopoiesis. Monochorionic Dizygotic twins tends to exhibit blood chimerism. There is no established theory to sustantiate whether chimerism occurs in monochorionic monozygotic twins, dichorionic dizygotic twins, dichorionic monozygotic twins and singleton pregnancies. Ref: Avery's Diseases of the Newborn By H. William Taeusch, Robea A. Ballard, Christine A. Gleason, Mary Ellen Avery, Page 61 Pathology of the human placenta By Ku Benirschke, Peter Kaufmann, Page 8