Ultrasound

Sound waves at a pitch higher that most human ears can register have the property of passing through fluid in a way that allows the reflected signals to be imaged. An example of how effective this can be is the ability Bats have evolved to resolve these signals  to the degree of precision that allows them to pick Mosquito's out of the air. Lacking the ability to project or sense these sounds ourselves, we have developed appliances indicate the imagery for us. One of these appliances that has garnered a lot of press in the last few years is the US Navy's use of High Frequency Sonar Using these frequencies allows sub mariners to image their surroundings as if they were looking at a landscape spread out before them. This level of detail requires a lot of energy in the form of sound projected into the water. There is ample evidence that marine mammals exposed to these energy levels experience so much pain that they will actually swim out of the ocean. Autopsies show that many of their eardrums have imploded and they are often bleeding from the ears. 

Another of these appliances is ultrasound imaging which is a non-invasive method of imaging internal body structure.  This is an inexpensive way to get coarse grained images which are adequate for many medical applications. One such application is getting a look at a developing fetus, which is done thousands of times every month in hospitals and clinics. The are no obvious negative effects on the developing fetus. Improvement of this technology allows for dynamic imaging which shows neuromotor activity - movement - and shows that there is often a reflexive response to the ultrasound stimuli as early as 6 weeks.

It would seem prudent to assume that injecting a lot of acoustic energy into the womb could have negative results and potential risk negation opportunities should be considered. One of these would be to match the density of the table on which the patient is prone with the density of the body as closely as possible. Doing so allows much of the unused acoustic energy to dissipate, rather than be reflected back into the womb. The reflected sound creates resonant standing waves where the energy can accumulate to many times it initial value in a small area. Given the complexity and delicacy of the task being undertaken and how artificial ultrasound frequencies and energy densities  to natural development, it would seem prudent to use the technology sparingly and with any precautions available when imaging a developing fetus.