I guess the thing is, people are saying, well, the risk is small, so if it reassures you, get it done. My problem with that is, WE DON"T KNOW THE RISKS. We don't know if they're very small or relatively large. X-rays, as Alegna pointed out, were used routinely for a while before it became apparent that they caused considerable risk of defects. I don't think the potential risk of ultrasounds is as scary as with X-rays (which carry a huge risk), because with X-rays the damage was easy to see once the damaged babies who had been subjected to prenatal X-rays started to be born. And we don't see waves of severely damaged babies, where the damage is clearly due to ultrasounds. But that certainly doesn't rule out that some damage is done. Perhaps subtle damage. Virtually no studies have been done on the safety of ultrasound. That is so mind-boggling to me.
Ultrasounds cause tiny pockets of intensely heated cells, and tiny air bubbles, within the fetus. There are called cavitation. We have NO idea of the effect of cavitation upon the developing fetus. What if the small pockets of intense heat are caused in the brain? Maybe the baby will not be brain-damaged, but merely won't be as smart as it would otherwise have been. Or maybe autism will be the result. What if cavitation occurs in the kidney? Maybe kidney damage will occur that won't be clinically noticeable until the kid is in his/her 20's. Maybe the damage will be done to the developing ovaries, and PCOS will result--which the baby won't know or care about until she is grown up and trying to have a baby of her own. Maybe the liver will be slightly damaged, and that will become apparent several decades later. Now maybe none of these things happens, or happens very rarely... but we just don't know. When we don't know the risk, and there is no known benefit (i.e., better outcomes are NOT seen with routine ultrasound), then TO ME it seems like it's obvious that it's better not to have an ultrasound done in the absence of some indication.
Having said all that, I know not everybody thinks the way I do or balances risk/benefit equations the same way, and I certainly don't judge or think harshly of anybody who chooses to get an ultrasound for peace of mind. I just think that the confidence in their safety and helpfulness is vastly overrated in the public eye. And I know it's hard to buck the trend--the vast majority of Americans thinks they're perfectly safe, and indeed that it's somehow dangerous NOT to have one. And even OBs, sadly, perpetuate these falsehoods, though they ought to be the ones to educate us away from them.
Catherine