My baby boy is big

Cierra • This mine and my husband`s third child. We have a handsome boy and a perfect little girl. We are expecting another boy and couldn`t be happier
I went to the doctor yesterday and I am measuring 27cm long which is huge for 24 weeks. He put me f an for a sonogram for my next appointment to see why. Should I be worried?? This is pregnancy 3 for me and never had them say that.