I think its interesting that you say babys grow at different rates because my Sonographer who is also a specialist Ob at Nepean said that bubs are all the same size up to 21 weeks which is when they start putting on fat.

I am measureing a week behind my EDD going off LMP. He said that i ovulated late and im a week behind the hospital dates. I asked him if there was any chance that this bub is just a bit smaller and my dates are correct and this is when he said about them all growing and being the same size and length. Its annoying to get different opinions.
My Ob at hospital said he wasnt going to alter the dates to marry up with the U/S but last app. he wrote down the u/s date.....arrrrrrggghhhh.