Intra-Amniotic Pressure Reduction in Twin-Twin Transfusion Syndrome

OBJECTIVE: Our purpose was to measure intra-amniotic pressure before and after decompression amniocentesis in twin-twin transfusion syndrome. STUDY DESIGN: Intra-amniotic pressures were measured during decompression amniocentesis on 18 occasions in 5 pregnancies complicated by twin-twin transfusion syndrome. The intra-amniotic pressure was determined with a water manometer before and after removal of amniotic fluid. For comparison, intra-amniotic pressure was determined in 10 uncomplicated gestations. RESULTS: Initial intra-amniotic pressures in twin-twin transfusion gestations (mean, 17.2 ± 5.2 cm H₂O; range, 5.5 to 33.0 cm H₂O) were higher than those of the uncomplicated gestations (mean, 8.4 ± 3.3 cm H₂O; range, 3.5 to 13.5 cm H₂O; p < 0.002). Intra-amniotic pressures following therapeutic amniocentesis (mean, 10.9 ± 5.1 cm H₂O; range, 3.5 to 23.0 cm H₂O) were not different from those of the uncomplicated gestations (p = 0.16). CONCLUSION: The intra-amniotic pressure in twin-twin transfusion gestations is higher than that of the uncomplicated gestation. Decompression amniocentesis reduces intra-amniotic pressure to that of the uncomplicated gestation.