Teratologic evaluation of rats prenatally exposed to pulsed-wave ultrasound

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 waterfilled ultrasound exposure tank, were scanned with 3‐MHz pw ultrasound at levels of 0, 2, 20 or 30 W/cm2 lSPTA (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 (