Teratologic evaluation of rats prenatally exposed to pulsed‐wave ultrasound

Abstract

While there are no known risks associated with diagnostic ultrasound, uncertainty about the safety of prenatal ultrasound exposure remains. The purpose of the present experiment was to evaluate the teratogenic potential of pulsed-wave (pw) ultrasound in rats, in the absence of maternal anesthesia or restraint. Pregnant CD rats, trained to remain immobile in a water-filled ultrasound exposure tank, were scanned with 3-MHz pw ultrasound at levels of 0, 2, 20 or 30 W/cm2 ISPTA (spatial peak, temporal average intensity) on gestational days 4-19 for approximately 10 min/day. Examination of fetuses on E20 revealed no increase in skeletal or visceral malformations in groups exposed to pw ultrasound in utero. The number of implantations/dam was significantly increased in all pw ultrasound exposure groups compared to sham-exposed animals and, in a possibly related finding, resorptions were increased in the two highest exposure groups. Although significantly increased compared to controls, resorption frequencies in these groups were low (< 10%). No exposure-related changes in fetal weights were observed in offspring of rats scanned with pw ultrasound during gestation. The results indicate that, under the conditions described, no overt embryotoxicity is associated with gestational exposure to pw ultrasound intensities of up to 30 W/cm2.

Biological effects of high-frequency ultrasound exposure during mouse organogenesis

“…Effects of diagnostic US exposure on fetal body weight have also been reported in some studies, but not in others (Fisher et al 1994). Previous investigations of bioeffects associated with high-frequency US biomicroscopy have included the anterior segment of the rabbit eye, in which exposures with the focal point placed on the cornea resulted in no evidence of changes in the tissue (50 MHz, IM SPTA.3 34.2 mW/cm 2 , 30 min, 10-kHz pulse-repetition frequency, PRF; Silverman et al 2001).…”

“…The data on the effect of in utero exposure of mice to diagnostic US is highly inconsistent, with some studies reporting effects on embryonic/fetal viability and/or increased malformation rates, but others have found no effects (reviewed in Fisher et al 1994). Effects of diagnostic US exposure on fetal body weight have also been reported in some studies, but not in others (Fisher et al 1994).…”

“…Calculated values for heart short axis (SA), long axis (LA) and weight and kidney short axis (SA), long axis (LA) and weight of pups born to five pregnant females exposed to us and/or anesthetic at 8.5 or 10.5 days of gestation Cage control Anesthetic-exposed B-mode-exposed Doppler-exposed Williams 1990). The use of anesthesia or restraint during insonation could potentially confound the experimental results because both are associated with developmental toxicity (reviewed in Fisher et al 1994). Restraint stress is a well-known teratogen; however, there is no evidence that restraint of anesthetically induced unconscious mothers causes significant alterations in pregnancy outcome or postnatal behavior (Jensh and Brent 1999).…”

Cincinnati water maze: A review of the development, methods, and evidence as a test of egocentric learning and memory

“…In a collaborative project with ultrasound engineers and ultrasound physicians, we developed an ultrasound exposure system for rats (Smith et al, 1990). We used the system to test for teratogenic effects of continuous (Vorhees et al, 1991b) or pulsed ultrasound (Fisher et al, 1993) and in both cases found no teratogenicity in the CWM under standard lighting. We next used the same system to evaluate the neurobehavioral effects of prenatal continuous or pulsed wave ultrasound and again found no effects in the CWM under standard room lighting (Vorhees et al, 1994c; Fisher et al, 1996).…”

The safe use of non‐medical ultrasound

“…Applied to medicine, this forms the basis of the ‘ primum non nocere ’ (first do no harm) approach as well as the ALARA (as low as reasonably achievable) principle. Effects of insonating waves have been demonstrated in animals10–16 and investigations into several biological effects in humans have been documented in the literature, the conclusions of which are summarized in the AIUM epidemiology statement17. There is very little information on energy output and exposure in clinical obstetric ultrasound.…”