Effects of intravenous terbutaline on maternal circulation and fetal heart activity

The effects of terbutaline on maternal circulation and fetal heart activity were studied in 15 healthy pregnant women admitted for external cephalic version. The two-step infusion of terbutaline (5-10 micrograms/min) resulted in increases in maternal heart rate (p less than 0.001), cardiac output (p less than 0.001), systolic arterial pressure (p less than 0.001) and pulse pressure (p less than 0.001), while diastolic arterial pressure (p less than 0.001) and total peripheral vascular resistance (p less than 0.001) were reduced. Mean arterial pressure was unchanged after the infusion. Fetal heart activity assessed by cardiotocography showed a gradual increase in baseline fetal heart rate (p less than 0.01) and an increased percentage acceleration time (p less than 0.05). Fetal movements also increased during the infusion (p less than 0.05). The terbutaline infusion had a positive inotropic effect and produced decreased systemic vascular resistance in the pregnant woman, and placental transfer of the drug resulted in increased fetal heart activity. The potential influence of the drug-induced changes in maternal hemodynamics on utero-placental perfusion require further investigation.