I don't know anything about IUGR but I do know about our bodies copying themselves and it sounds like yours is doing the same thing it has done in the past. If you are measuring 2 weeks behind already, then I think it would be safe to assume that your doctor is right. I know that with my pregnancies, I had PIH and the first 3, like you were close together, and then there was 4 and a half years between the 3rd and 4th babies and I thought that because of the time in between these babies that I wouldn't have the same problem but I did. In fact it was worse. Listen to your doctor. With your size I would think that you would probably run a slightly higher risk of having a smaller baby anyway. It doesn't sound like you are a very big person yourself... I'm sure that its suggested for you to gain more than the average amount of weight while you are pregnant. I don't know, it just what I have read, typically smaller women tend to need to gain a bit more while they are pregnant. But don't be fooled, most often, not always, but most often our bodies do what they know and it sounds like this time is the same as before. You should have an appointment coming up, talk to your doctor about ways to avoid having an early/small baby.
S.