Factors influencing aortocaval compression in late pregnancy

Abstract

The circulatory effects of postural change in late pregnancy were investigated in 20 healthy pregnant women. Maximum stroke volume (93.2 ± 11.9 ml) was recorded with the subject in the left lateral position and was significantly (p < 0.001) reduced in the supine, right lateral, and lithotomy positions, but was largely unchanged in the standing motionless position (89.9 ± 12.6 ml). Diastolic, systolic, and mean arterial blood pressures and total peripheral vascular resistance were significantly (p < 0.001) increased in the supine, right lateral, lithotomy, and upright motionless positions when compared to the same variables in the left lateral position. The following factors were found to be significantly correlated to the hemodynamic response to the supine recumbent position: maternal age (p < 0.05), the position of the fetus in the uterus (p < 0.05), and systolic (p < 0.001) and diastolic (p < 0.001) blood pressures measured with the subject in the left lateral position. The implications of the present findings for modern obstetric delivery care and the etiology of the supine hypotensive syndrome are discussed.