Changes in fetal hemodynamics with ritodrine tocolysis

Objective To evaluate the effect of ritodrine on the fetalcardiovascular system. Methods Cardiac and extracardiac Doppler waveforms wererecorded in 12 fetuses prior to and during ritodrine therapyused for preterm labor. Maternal and fetal heart rates, theDoppler pulsatility indices of the umbilical artery, middlecerebral artery, descending thoracic aorta and renal artery,and time velocity integrals of the atrioventricular valves andthe ductus arteriosus, were measured. Results Ritodrine infusion caused an increase in maternaland fetal heart rates, the left cardiac output as measured bythe product of time velocity integral and heart rate, and thepulsatility index of the middle cerebral artery, and a decreasein the pulsatility index of the umbilical artery. Conclusions Ritodrine infusion may alter placental andcerebral blood flow and may have a selective effect on the leftside of the heart. INTRODUCTION Ritodrine is a commonly used beta sympathomimetic agent fortocolysis in several countries. It causes maternal tachycardia,a rise in systolic pressure, and a decrease in diastolic pressure