Controlled amnioreduction outcome
Amniotic pressures were measured prior, during and at the end of the AR procedure. The pattern of the decreasing amniotic pressure during removal of the excess volume of fluid is depicted in Figure 1. The pressures reached a plateau at the end of the completed procedures except the 5 patients in which AR was interrupted due to the patient discomfort. There was no correlation between the amount of drained amniotic volume, duration of AR procedure and the reached pressure plateau. The obtained amniotic pressures were compared with the normal pressures as reported by Fisket al 16. The pressure drop at each AR procedure is shown in Figure 2 along with the reference range for singleton pregnancies. The initial pressures for all patients were higher than the normal range. As expected, the post-procedure pressures were lowered to be in the reference range in 61.1% of cases while slightly higher than the norm in 38.9%.
The umbilical artery S/D values that were measured for each fetus pre- and post-procedure are compared with the reference range for singleton pregnancies 25. The initial S/D ratio of recipient was higher (mean percent difference is 29.3%) in 3 cases, while in the rest cases the donor twin had the higher S/D ratio. Absence of end diastolic flow (AEDF) occurred in 3 donors, and thus, an arbitrary value of 9 was given as the initial one for graphic representation. All these donors showed some hemodynamic improvement after the AR. In general, most (23 of 36, i.e., 63.8%) of the post-procedure S/D ratio became within the normal range according to the given weeks of gestation. Comparison of inter-twin differences of S/D ratio values in pre- and post-procedure did not show some tendency: inter-pair differences were significantly decreased after the procedure in 7 twins, increased in 5 twins and were unchanged in 6 cases.