I think the weight rules are a bit too stringent, and their major failing is that they look more at numbers than nutrients. I know the docs don't like more than a certain # of lbs but they are conducting their practise in an environment of fear of lawsuits so they take the CYA road and tell their moms to do what is ultimately the safest for the practise. If you don't have a clear cut case of diabetes, and are eating nutrient dense foods and not a bunch of junk, you will be growing a healthy baby that is a normal size for your body.
At this point, any further ultrasounds will be less and less and less accurate. They aren't that accurate to start and as the baby gets bigger they get worse. I had one baby who was supposedly 7+ lb come out at 5lb 13oz. Late ultrasounds are accurate to "+/- 2lb" so that means there's a four lb range the baby could be... in other words, it isn't really more accurate than a guess.
Here's some insight on the weight issue in the words of a midwife -
"My thing with clients is "How do you eat? What do you eat?"
I am not concerned as much with numbers on a scale as I am with PROPER nutrition throughout pregnancy. I am amazed at how many women do not have any idea about correct diet throughout pregnancy and what a difference it makes in their general health as well as the labor , delivery and post partum period.
I do have my clients weigh themselves each visit, but I also keep a close check on how they are doing with their eating habits. ON AN AVERAGE, my clients gain between 25-45 lbs. But, if they are taking in what they need to be, their body will determine the pounds gained. Many women have a "JUMP" somewhere in their second trimester. I have seen it over and over. So, I'm not concerned when a mom comes in between four and six months and has gained seven to ten pounds in a month. I would be concerned if she did that every time, but knowing what the body needs at different stages of pregnancy helps monitor the overall picture.
By the way, the babies born to these women average between 8 - 10 pounds. Healthy and no problems with birthing. They are off to a good start.
My bottom line: Don't JUST look at the numbers, look at the intake."