So confused!

Has anyone had the issue of the baby is growing perfectly everywhere except the stomach? Her tummy is growing two weeks behind and the dr started talking about going a week at a time to monitor the growth and seeing if we need to look into early delivery, bed rest, things like that. Just confused on what's happening. They gave me steroids to help her lungs grow just as a precaution. I'm I credibly happy with my ob and glad she's taking all these precautionary measures she just threw out a lot of information at once