Supine hypotensive syndrome.

Abstract

Supine hypotensive syndrome is characterized by severe supine symptoms and hypotension in late pregnancy, which compel the unconstrained subject to change position. Rarely, it may manifest even from the fifth month of pregnancy or postpartum, as well as in the pelvic tilt or sitting positions. Although inferior vena cava compression, influenced primarily by the size of the uterus and exact maternal and fetal position, is the major determinant in its development, other factors may also be important in modulating the circulatory effects of such compression. Advance recognition of susceptibility to the syndrome depends on a history of severe supine symptoms or supine intolerance and an increase in maternal heart rate and decrease in pulse pressure in the supine position. As there seems to be a spectrum of severity from minimal central cardiovascular alterations to severe syncopal shock resulting from supine inferior vena cava compression, it is difficult to define a cutoff point at which the syndrome occurs. Although usually recognizable by maternal symptoms, severe hypotension without symptoms has been reported on three occasions.