Postural blood pressure differences in pregnancy: A prospective study of blood pressure differences between supine and left lateral position as measured by ultrasound

Abstract

Differences in blood pressure between the supine and left lateral positions were studied in pregnant subjects under standardized conditions with an automated ultrasound device. Cross-sectional studies were performed in 125 nulliparous pregnant women after the twenty-eighth week of amenorrhea and in 42 nonpregnant controls. Arterial blood pressure in the left lateral position was lower than in the supine position. This difference was due largely to differences in hydrostatic pressure. Large errors in measurement and regression to the mean contributed to a wide spread in measured values. Neither hypertension nor pregnancy alone gave an enhanced postural difference in blood pressure. Hypertension in pregnancy was associated with a significantly larger positional change in diastolic blood pressure (D) than in systolic blood pressure (S). This study pleads for a standardized procedure for the measurement of blood pressure in gravidas in the supine position, for the detection of peripheral vasoconstriction in the supine position, and to compare clinical blood pressure studies in different institutions.