Baby measuring big???

I was 19wks 2 days when I had the anatomy scan. He's been measuring a wk ahead at both of my previous scans(8wks, 12wks) and measured 21wks 2days at this last one.  How ever,his femur  measurement  put him at 24 wks 2 days and his arm measurement was at 23wk 2days. He is weighing in at 13oz already. Should I expect a big baby, with long legs? Both of my previous children   Measured the same as the GA. I'm just a little confused as to why his legs are so long. I'm 5'2 and my husband is 5'10. Neither of us are very tall.  Both previous children were 21 inches long at birth.