OCCASIONAL REVIEW: Twin‐Twin Transfusion Syndrome: Intraamniotic Pressure Measurement in the Assessment of Volume Reduction at Serial Amniocenteses

EDITORIAL COMMENT: We accepted this paper for publication because we consider it contains important information on management of patients with acute polyhydramnios. However the editorial committee considers that there is still doubt regarding how commonly fetofetal transfusion is the aetiological mechanism of the acute polyhydramnios syndrome seen in uniovular twins. We have reviewed the clinical data of the 13 cases reported by Steinberg and colleagues(A) with a particular emphasis on the haemoglobin discrepancies between the twins and whether or not the polyhydramnios was associated with the recipient twin. The findings were that there were only 4 cases where there were haemoglobin measurements performed on both twins; in only 2 of the 4 was the difference more than 4 g/dL and in both cases the smaller twin had a higher haemoglobin value. In 1 of the cases the haemoglobin values of the twins were 5.5 and 9.8 g/dL respectively and the smaller twin had the higher haemoglobin value; there was polyhydramnios in both sacs. In the other case where there was a haemoglobin discrepancy of more than 4 g/dL the smaller twin had the higher haemoglobin (20.7 g/dL) and the larger twin had a haemoglobin value of 16.6 g/dL and only this larger twin had a polyhydramniotic sac. It seems to us that the mechanism of acute polyhydramnios may not be the same in all cases and it is not proven that fetofetal haemorrhage is a convincing explanation for all cases. One of the problems in elucidating the problem is that these patients are often incompletely documented because of stillbirth or uncertainty as to whether the small or large twin occupied the polyhydramniotic sac. Summary: Two cases of severe twin‐twin transfusion syndrome are described. In both, serial amniocenteses were followed by resolution of the disordered inter‐twin haemodynamics with 4 intact term survivors. In all reports to date of aggressive reduction with or without successful outcome, volume reduction has been dictated by subjective or semiquantitative ultrasonic estimates of liquor volume. With the use of intraamniotic pressure estimation we describe a more rational basis for the removal of these large volumes of amniotic fluid.