Severe Twin‐Twin Transfusion Syndrome: Current Management Concepts

EDITORIAL COMMENT: This and the following paper illustrate that serial amniocentesis has resulted in a marked improvement of results in women with uniovular twins with the twin‐twin transfusion syndrome where one twin has polyhydramnios. Since the perinatal survival rate has been approximately quadrupled using this technique, we would respectfully disagree with the advocacy of a controlled trial to assess the value of therapeutic amniocentesis in these cases. Our editorial committee considers that the case has been made, and that it would probably be unethical to withhold treatment in a condition which untreated has a perinatal mortality rate of 60–100%. However we agree that our understanding of this disorder remains incomplete. The size of these series suggests that the condition is becoming more common which is surely not possible. We require an audit of a community series ‐ ideally from the perinatal units of each Australian State ‐ to calculate the contribution of polyhydramnios (twin‐twin transfusion syndrome) to the perinatal mortality rate in twin pregnancy. Consideration of the rates that existed when the State perinatal units were established 9 years ago should show if the incidence of the condition has changed, and also give an idea of the possible contribution of treatment of twin‐twin transfusion to the improvement that has occurred in results of twin pregnancy e.g. in 1985 in Victoria the perinatal mortality rate was 4.3% in 1,422 infants bom from multiple pregnancies; in 1992 the comparable mortality rate was 3.2% in 1,755 infants born from multiple pregnancies. How many deaths may be prevented by early diagnosis and treatment of twin‐twin transfusion syndrome by serial amniocenteses? Multiple pregnancy remains an important cause of perinatal mortality ‐ 10.9% (56 of 516) of all perinatal deaths of infants with birth‐weight of 500 g or more in Victoria in 1992. This paper does not consider whether the polyhydramnios in these cases is acute or chronic. Perhaps timely diagnosis and treatment prevents the onset of acute polyhydramnios that one previously associated with a severely distressed mother who required delivery which resulted in her infants dying from prematurity. Does successful treatment of polyhydramnios in twin‐twin transfusion syndrome, by reduction of pressure in the polyhydramniotic sac, cause cessation of the twin to twin transfusion?; does treatment result in the twins no longer having discordant haemoglobin values?, a difference that was previously required for verification of the diagnosis. The important data in the cases described in this and the following paper indicate that this fascinating complication of monozygotic twins continues to puzzle us. Author's response to editorial comment: The clinical opinions at King Edward Memorial Hospital are that there appears to be an increase in the number of cases of oligohydramnios‐polyhydramnios sequence seen antenatally but our information is confounded by the widespread application of ultrasound and prompt referral once an abnormality is detected. The latter is influenced greatly by the excellence of our neonatal paediatric service. I would comment that the published series of therapeutic amniocentesis are noncontrolled and suffer significant bias, hence the concept of conducting a randomized controlled trial. Whilst superficially the results are excellent, therapeutic amniocentesis has commenced in an era of excellent survival for the preterm fetus, and the older studies in which this technique was not employed did not have such an advantage. Hence, obstetricians are aggressive in delivering these infants in optimal condition with liberal use ofCaesarean section and premature interruption of pregnancy for evidence of fetal compromise. The argument against a randomized study is that there is no other safe, widely applicable therapy available for the oligohydramnios‐polyhydramnios sequence. Summary: The presence of functioning vascular anastomoses within the monochorionic placentation of a monozygotic twin pregnancy is responsible for the twin‐ twin transfusion syndrome. This is a heterogeneous disorder with a wide spectrum of severity. In the most severe form it results in the oligohydramnios‐polyhydramnios sequence with a marked disparity in intertwin biometry and amniotic fluid volume. Without therapy, the perinatal mortality of severe twin‐twin transfusion syndrome is 60–100%. Several therapeutic interventions have been attempted with therapeutic amniocentesis producing the most consistent improvement in fetal survival rates. The outcome of 10 cases of severe twin‐twin transfusion syndrome, presenting as the oligohydramnios‐polyhydramnios sequence, is presented. Gestational age at presentation ranged from 20–34 weeks. Three fetuses were hydropic at initial presentation and of these only 1 survived. All cases were treated with serial aggressive therapeutic amniocentesis, the number of procedures ranging from 1–9/patient. The volume of amniotic fluid removed ranged from 3,200‐14,000 mL. Gestation was prolonged a mean of 46 days (range 1–106 days). The perinatal survival rate was 65% (13/20 infants). Preterm premature rupture of membranes and secondary preterm birth complicated 1 pregnancy treated with therapeutic amniocentesis. Short‐term morbidity in the liveborn infants was predominantly secondary to prematurity and renal cortical necrosis. Severe twin‐twin transfusion syndrome is the most common aetiology of the oligohydramnios‐polyhydramnios sequence. Therapeutic amniocentesis offers an intervention that may reduce the high perinatal loss rate previously observed with this disorder.