baby weight

I been seeing alot of post where they are 20w and some are even saying how much the baby weight already. But when i went in and got my ultrasound done at 20w they didnt tell me that just told me he was a week and 5 days behind growth. Is that why i didnt get told how much he was weighting? I go back in 4 weeks to do another ultrasound to check on him will they tell me then?