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雙胞胎的輸血症候群（Twin-to-twin transfusion syndrome）發生比率約為monochorial twins 之25%，（Galea et al., 1982）但事實上比例應該更高，且有程度上之區別，依Quintero Classification 共有五期（如附表），從羊水過多過少（poly-olighydramnios? sequence） 至其中一胎胎死腹中。另一種情況和TTTS類似者為Acardiac Twin (TRAP sequence, Twin reversed-arterial-perfusion)，也是因為Twins之間血管有明顯交通血流交換造成（hemodynamically significant shunts）。
做過產科的醫師都知道，一旦遇上TTTS的case，以往總是兩手一攤，不知如何是好，即使是幸運存活下來，往後所造成的腦部病變也難以預測，一般而言，愈早出現TTTS之case其預後愈差（Bebbington and Wittmann,1989），現今證明不但無法改善預後，而且也無法預防Fetal brain damage.
雙胞胎的輸血症候群之原因來自於血管之交通，所以根本上的治療也應是阻斷血流以避免不均衡之結果（Vascular Volume discrepancy），除了解決生長一大一小，羊水一多一少（破水問題），心臟、膀胱、臍帶一大一小（Heart failure 及? pulmonary hypoplasia）之問題外，以目前社會高標準之期望，產前診斷及治療目標就要減少mortality及morbidity，尤其是Neurological sequalae多出40倍，(Pharoah, 2000)，而又以發生於Vein to? vein anastomosis較為常見 。
超音波於TTTS之運用，除了可以診斷外（Classification, severity, brain injury）另外可以追蹤其變化及加以治療，本部詹耀龍醫師出國進修後，能得到Dr. Quintero 之真傳，利用Laser阻斷血管血流，以避免後遺症。因為只要有TTTS即有可能造成cerbral pathology，特別是發生hypotension, shock 和one fetal death，原因也可能來自於emboli，這種現象也可能早至16 weeks即會發生。（Anderson et al., 1990）在本刊專輯就有一病例。
Quintero has proposed 5 stages of TTTS based on ultrasound findings:
Stage I: This is the initial way that TTTS is seen on ultrasound. ?In stage I, there is oligohydramnios in the donor’s sac with an MVP of ?2 centimeters or less (3/4 inch) and polyhydramnios in the recipient’s sac with a maximum vertical pocket of fluid of 8 centimeters or more (just over 3 inches). ?The bladder of the donor baby is still seen.
Stage II: As defined above, there is polyhydramnios and oligohydramnios but the bladder is no longer seen in the donor twin during the ultrasound evaluation.
Stage III: Blood flow in the fetus can be measured with a special type of ultrasound called Doppler. ?In addition to the findings of Stages I and II, careful study of the blood flow in the umbilical cord and fetal ductus venosus (the large blood vessel in the fetus that returns blood to the heart from the placenta) reveals abnormal patterns in these patterns can occur in either or both fetuses.? In the umbilical cord, the diastolic flow can be either absent or reversed in the umbilical artery. ?This pattern is usually seen in the donor twin.? In the ductus venosus, the diastolic flow can either be absent or reversed. ?This pattern is usually see in the recipient twin due to early heart failure. ?The recipient twin can also exhibit leakage across the main valve on the right side of the heart – this is known as tricuspid regurgitation.
Stage IV: One or both babies shows signs of hydrops. This means there is excess fluid in ?parts of the baby such as swelling of the skin around the head (scalp edema), fluid in the abdomen (ascites), fluid around the lungs (pleural effusions) or fluid around the heart (pericardial effusion). These findings are evidence of heart failure and are typically seen in the recipient twin.
Stage V: One or both babies have died. |
