INDOMETHACIN-INDUCED PLACENTAL VASODILATION - ASSOCIATION WITH FETAL DUCTAL CONSTRICTION

Objectives: 1. To compare the pulsatility index (PI) of the umbilical artery in two groups of fetuses versus controls: those who had ductal constriction after maternal indomethacin therapy and those who had no ductal constriction. 2. To evaluate the paired changes in umbilical ar tery PI in the individual fetus who had ductal constriction. Methods: Image-directed pulsed Doppler echocardiography was performed in two gr oups of fetuses, 48 fetuses from normal pregnancies and 44 fetuses who se mothers received indomethacin for premature labor. Maximal fetal bl ood velocity waveforms of ductus arteriosus and umbilical artery were recorded and analyzed for maximal, end-diastolic, and mean velocity. T he PIs of these two vessels were calculated. Results: The umbilical ar tery PI in studies with ductal constriction was significantly lower th an those in the group without ductal constriction and the normal contr ol. In the individual fetus who had ductal constriction, the umbilical artery PI was also decreased significantly when the ductal constricti on occurred compared with the baseline value. Conclusions: Indomethaci n exposure sufficient to cause ductal constriction has an effect on th e placental blood velocity pattern. The decrease in PI suggested decre ased placental resistance, perhaps by the differential effect of indom ethacin on the production of prostacyclin and thromboxane or by the me chanical effect of uterine relaxation.