Biological effects and possible hazards.

Confirmed experimental mammalian biological effects have occurred at intensities above 100 mW/cm2. Reports (mostly with in vitro cell systems) of effects using diagnostic ultrasound have not been independently confirmed. In most cases the mechanisms of action by which reported biological effects have occurred are unknown. The occurrence of cavitation in tissues is not well documented. For these reasons it is difficult and inappropriate to make conclusions or determinations regarding the clinical safety of diagnostic ultrasound based on the current experimental data available. Epidemiological studies published in the scientific literature have indicated no effects of diagnostic ultrasound on fetus or mother. However, the experimental epidemiological data available are not sufficient to make final judgements regarding safety of diagnostic ultrasound. Its benefits are well known and documented. The approach to be taken in this situation is to use diagnostic ultrasound when medically indicated and to minimize exposure by minimizing time and intensity. There is little scientific literature support for the postulate that diagnostic ultrasound as currently used is hazardous. We believe that ultrasound is safe enough to use in any pregnant woman at any gestational age as often as the clinical indications are present, without need for informed consent (Hohler, 1982). However, since our experimental and epidemiological basis for risk assessment is far from complete, it is not wise to use diagnostic ultrasound indiscriminately.