Feto-fetal transfusion syndrome

According to various authors1-3 vascular anastomosis is present in 85-100% of all monochorial placentae, and may allow the unbalanced transfer of blood from one twin to another. Such vascular communications may be obvious on inspection or on injection ofdye into the placental vessels. The most common anastomosis is of direct arterio-arterial type, but some are veno-venous. Perhaps of greater pathological significance is artero-venous anastomosis between the two circulatory systems. The feto-fetal transfusion syndrome (FFTS) is one of the contributory factors to the increased morbidity and mortality in monozygotic twin pregnancies. It has been suggested that two types of FFTS exist: a chronic form existing during pregnancy, and an acute form occurring only during parturition. In chronic FFTS the donor twin, owing to an unbalanced transfer of blood, is generally hypovolaemic and anaemic, and shows varying degrees of growth retardation. In severe cases this twin may die in utero resulting in a fetus papyraceus at birth. The recipient twin however is hypervolaemic, polycythaemic, and is often the larger of the two. In severe cases this twin may develop cardiac hypertrophy and congestive cardiac failure. Furthermore increased urine production by this twin may lead to hydramnios and precipitate premature labour.4 5 In acute FFTS the twins are generally similar in weight and length but one is polycythaemic and hypervolaemic and the other anaemic and hypovolaemic.