Comment by verisimi

Using the example of a laser - you can have a powerful laser that can burn through metal. A far weaker laser (many magnitudes weaker) could still damage eye sight. Alternatively, water erodes mountains eventually.

I don't think you can argue that ultrasound imaging is harmless or a treatment/dose. It might be that it does nothing. It might also be that it does something (like when it destroys cancer cells) only its far milder, and not an obvious observation.

PS I know there are mild ultrasound devices to aid muscle recovery. These devices do something, presumably. If mild devices are acknowledged to impact muscles etc, some (mild probably) effect is occuring. Given there are occasions where these devices are known to have an impact on adults, why should we presume that there is no impact on the technology when it is looking at a developing foetus?

PPS Even in studies that say there is 'no effect' from ultrasound imaging, there is a tolerance of up to 10% difference between the control and the subjects.

PPPS And of course, sometimes the control is 'children who have only had 1 ultrasound' vs 'children who have 2 or more ultrasounds' - ie the control is not 'children who have who have had no ultrasounds' - ie we do not get true control studies.