Changes in fetal hemodynamics with ritodrine tocolysis

Objective To evaluate the effect of ritodrine on the fetal cardiovascular s ystem. Methods Cardiac and extracardiac Doppler waveforms were recorded in 12 fetu ses prior to and during ritodrine therapy used for preterm labor. Maternal and fetal heart rates, the Doppler pulsatility indices of the umbilical art ery, middle cerebral artery, descending thoracic aorta and renal artery, an d time velocity integrals of the atrioventricular valves and the ductus art eriosus, were measured. Results Ritodrine infusion caused an increase in maternal and fetal heart r ates, the left cardiac output as measured by the product of time velocity i ntegral and heart rate, and the pulsatility, index of the middle cerebral a rtery, and a decrease in the pulsatility index of the umbilical artery. Conclusions Ritodrine infusion may alter placental and cerebral blood flow and may, have a selective effect on the left side of the heart.