Nonstress test and maternal position.

Abstract

Antepartum evaluation of 225 low-risk primipara and 262 high-risk primipara and multipara using nonstress testing revealed 53 to be nonreactive when the test was performed in the supine position. When the test was repeated in the lateral decubitus position, it became reactive nonstress testing in 21 of these patients. This group of patients with a supine nonreactive nonstress test and a lateral reactive nonstress test demonstrated an associated compression of the abdominal aorta by the pregnant uterus in the supine, but not the lateral position. This study distinguishes three types of nonreactive nonstress tests: those due to placental insufficiency, those resulting from compression of the abdominal aorta by the pregnant uterus, and the falsely nonreactive. The percentage of false nonreactive nonstress tests results will be reduced by performing the test in the lateral decubitus position.