53.美莉產檢時超音波發現，此雙胞胎有兩個羊膜腔，但共用一個胎盤，會有發生雙胞胎間輸血 症候群（twin-to-twin transfusion syndrome）的風險，關於雙胞胎間輸血症候群（TTTS）， 下列敘述何者錯誤？
(A)TTTS發生原因目前認為和共用胎盤，且兩個胎兒間的血管相通（vascular anastomosis） 造成血流不平衡有關
(B)recipient的血液容積增加，會造成羊水過多，嚴重時會有心臟衰竭的現象
(C)donor的血液供給recipient，造成donor的血液容積下降，胎兒腎臟灌流（renal perfusion）下降，所以尿量變少，會使羊水過少（oligohydramnios），嚴重時超音波下 donor膀胱會看不到，且常被推擠至一角落（stuck twin）
(D)美莉的兩個雙胞胎間如果體重差異超過30%，就可診斷為TTTS

 It is the combination of oligohydramnios and polyhydramnios in a MC twin pair seen by ultrasound that indicates the diagnosis of TTTS.

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WIKI 

Quintero Stages

A staging system is commonly used to classify the severity of TTTS.^[3]

Stage I: A small amount of amniotic fluid (oligohydramnios) is found around the donor twin and a large amount of amniotic fluid (polyhydramnios) is found around the recipient twin.

Stage II: In addition to the description above, the ultrasound is not able to identify the bladder in the donor twin.

Stage III: In addition to the characteristics of Stages I and II, there is abnormal blood flow in the umbilical cords of the twins.

Stage IV: In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (fetal hydrops).

Stage V: In addition to all of the above findings, one of the twins has died. This can happen to either twin. The risk to either the donor or the recipient is roughly equal & is quite high in Stage II or higher TTTS.