Effect of Amniotomy on Uteroplacental and Fetoplacental Flow Velocity Waveforms

ABSTRACT

Artificial rupture of fetal amnionic membranes is frequently performed in normally progressing spontaneous labor, although the maternal and fetal effects of the procedure have not been clearly defined. The effect of elective amniotomy on placental impedance to blood flow in the umbilical artery and arcuate branches of the uterine artery was determined by analysis of blood flow velocity waveforms (FVWs) recorded with continuous wave Doppler ultrasound in 15 pregnant women at term. All patients were in spontaneous, normally progressing labor after an uneventful pregnancy. Electronic fetal heart rate monitoring and real-time ultrasound examination of the fetuses were unremarkable. FVWs were obtained immediately before and after amniotomy. Fourteen patients progressed to spontaneous vaginal delivery, and one patient underwent repeat cesarean section for arrest of dilation in the active phase of labor. No maternal, fetal, or neonatal complications were recorded. Calculated mean systolic/diastolic ratios of FVWs obtained before and after amniotomy were compared by means of Wilcoxon's signed rank test, and no significant differences were found. We conclude that early elective amniotomy exerts no demonstrable deleterious effect on impedance to uteropla-cental or fetoplacental blood flow in healthy women at term.