Effects of therapeutic amniocentesis on uterine and umbilical artery velocimetry in cases of severe symptomatic polyhydramnios.

The objective of this study was to determine the effects of removal of amniotic fluid in cases of symptomatic severe polyhydramnios on Doppler waveform indices of the uterine and umbilical arteries and flow velocities of the uterine arteries. Nine women underwent therapeutic amniocentesis during ten pregnancies for symptomatic polyhydramnios due to Beckwith-Wiedemann Syndrome (n = 1), esophageal atresia (n = 2), chorioangioma (n = 1), twin-twin transfusion syndrome (n = 3), a presumed autosomal recessive syndrome (n = 2), and an unbalanced double translocation (n = 1; partial dup 3q and partial del 9p syndrome). An average of 2.78 +/- 0.9 (range 1-4) 1 of fluid were removed at each procedure between the gestational ages of 18 and 34 weeks (mean of 28 weeks). The systolic/diastolic (S/D) ratio, pulsitility index (PI), and resistance index (RI) of the uterine and umbilical arteries were obtained before and after the procedure using color and pulsed Doppler. After angle correction, the peak systolic velocity (PSV) and mean velocity (MV) in centimeters/second (cm/s) of the uterine arteries were also determined. The presence or absence of a uterine artery waveform notch was determined. Dominant uterine arteries were defined as those with lower impedance indices or higher flow velocities. Statistical analysis was performed with the Wilcoxon signed-rank test. Significance was set at P < 0.05. There was a significant increase in the median value of the uterine artery MV (43.8 vs. 81.1 cm/s, P = 0.005) and PSV (74.2 vs. 125.5 cm/s, P = 0.007) after amniocentesis. The uterine S/D (3.0 vs. 1.84, P = 0.007), PI (1.12 vs. 0.68, P = 0.008), and RI (0.60 vs. 0.45, P = 0.005) impedance indices significantly decreased following amniocentesis. When uterine arteries were categorized as dominant vs. nondominant, there were greater improvements in impedance indices and flow velocities in the nondominant uterine arteries. There were three cases of unilateral and one case of bilateral early diastolic notches of the uterine artery waveforms which either resolved (n = 4) or improved (n = 1). There was no effect on the umbilical artery impedance indices. Therapeutic amniocentesis significantly improved uterine artery impedance indices and resulted in improved flow velocities, while there was no effect on umbilical artery waveform indices. The procedure resulted in the disappearance or improvement of the uterine waveform notch. Our findings suggest that in cases of severe polyhydramnios abnormal uterine artery velocimetry may not be due to lack of trophoblastic invasion of the spiral arteries but to increased intrauterine pressure secondary to polyhydramnios.