Sorry AnaB, I agree that we should be very careful in what we except as OK just because the doc says so. BUT with do respect I also think that some of these forums do more harm in promoting scare tactics. I clicked on all the links in your text that you linked to the studies you show overlap so at first when I saw all the links and thought oh my but most of them link to the same articles. All with quotes taken out of context and posted on different web sites. Most of the studies are from the mid 90'ies and if we where literally frying our kids brains for the past 15 years you would think there would have been more concluding studies done or even better evidence of that fact. My first child had around 15 ultrasounds (do to my wife measuring small and low fluid in the first month) he came out on the dd at 7lb14oz and is a very bright right handed child, he has 95 percentile growth rate and he started walking early. My Second had a routine 4-5 ultrasounds and came out 10lb2oz very bright right handed baby, walked early and both are in the best of health at 2&4.
What caught my attention about the studies was that the animals where given between 15min and 4hours! of ultrasound and the one study stated that usual ultrasound in the hospital last an hour. That is simply not true. I was at all of my children's ultra sounds and the longest lasted 3 minutes. The 3 minutes where interrupted and the wand moves around and exposes different parts of the baby for limited time. My wife is an ER doctor and uses ultrasound in anything from some chest pains to abdominal pains, these studies take under 2min. and give very precise imaging for diagnosing very serious problems. My point being that yes if you hold an ultrasound wand to your head everyday for a couple of hours while you watch TV then it will have a bad effect.
Imaging of any kind should be limited and the same goes for ultrasound but 2-3 ultrasounds of 3 minutes based on the articles you posted I doubt very much will hurt a baby.
We didn't want to know the gender but it was very evident in both cases and even a novice like me could see it. It was nice to see the heart beat and some features it made it all real especially with the first one.