Effects of continuous wave ultrasound on the mouse at different stages of gestation

Abstract

At five selected stages of gestation spanning days 1 through 13, mice were exposed dorsally to continuous wave ultrasound at 2 MHz, 1 W/cm2. At 200 and 400 W s/cm2 the pregnancy rate decreased and some mortality occurred. Survivors displayed reductions in mean maternal body weight gains in excess of those due to reductions in the mean number of viable fetuses and, in agreement with O'Brien [Ultrasound Meal. 2, 531–532 (1976)], decreases in mean fetal weights at necropsy before parturition. Dose response curves were obtained for fetal weight loss. Except possibly for a decrease in survival rate of fetuses exposed to 400 W s/cm2 on days 1 and 13, none of the stages of gestation was particularly sensitive to any of the effects observed. Light and electron microscope studies of ovarian, corpora lutean, and placental tissues revealed cytoplasmic and ultrastructural disruption; mitochondria showed the greatest sensitivity. The severity of ultrastructural damage appeared to be dose related. Measurements of temperature rises in the uterus to 45°C or more indicate a thermal mechanism as one cause of these effects. [Research supported by the National Institute of General Medical Sciences, Grant No. GM 22684.]