Ultrasound uses frequency between 2-12mhz to image soft tissues. Focused energy of that frequency will produce heat in the tissue. In a forming fetus, that heat is much more dangerous than it would be to a fully formed baby.

Heat may burst small cells, hinder growth resulting in low birth weight, possibly interfere with forming fetal brain tissues resulting in more ADHD children and adults. These are all just speculative consequences from the sudden projection of focused heat, but the body is a very sensitive organism and is heat/cold sensitive. When men wear briefs instead of boxers the sperm count goes down. This is a heat induced reduction of cell performance. So clearly the application of localized heat to fetal tissue cannot assist cell function, and must serve as a threat to cell efficiency/function.

When science understands more about frequency relationship as it regards to cellular processes, there will come about a whole new interest in the dangers of specific high frequency fields and their possible interference with biological processes. And as with all technologies that become widespread and reported as universally safe, eventually their downside is discovered. Think mercury amalgamated fillings.

While Lindy's statement has no substantive backing in medical papers, and is also not bound to get any real soon, it doesn't mean it is completely fallacious or in time we may not see warnings or time limits issued with ultrasounds.

The medical industry is all about money. These machines generate huge profits for their manufacturers and the manufacturers have a vested interest in keeping the background noise to a minimum. If someone could draw a statistical link from ultrasounds to any condition, the industry will move to protect itself from lawsuits with a precautionary wording and yet another release form.

No doubt ultrasound has saved many lives by its usefulness. There can also be little doubt that there does exist a downside as well, even if it is not yet fully defined or backed by 30 different studies.

The job of the parent is to become literate enough to understand any potential dangers and not approach technology like a child as a toy to be played with. Trusting one's doctor only goes so far as well. A doctor is a salesperson for medicine and medical procedures and makes their living from the purchase of same. This can also never be forgotten. Using sonograms (ultrasound), as is often done now, solely to determine the sex of the baby seems rather unwarranted and is just another way to generate revenues during pregnancy.