The placental blood flow was assessed by the 99mTc accumulation method in 10 normal pregnancies in the left lateral recumbent position accomplished by a 15.degree. wedge and in the supine position. The postural change caused a 17% decrease in the mean placental accumulation rate, which was not statistically significant. Patients (10) were moved from the left lateral recumbent position to the upright position, which caused a statistically significant 23% decrease in the mean accumulation rate. Other hemodynamic variables studied were the maternal heart rate and the systolic and diastolic blood pressures. The clinical significance of the hemodynamic changes produced by alterations in posture are briefly discussed.