Babies head measuring 2-3weeks behind

So I went in today for my 36 week check and strep b test. They did an ultrasound baby weighs 5lbs and 12oz but they said her head is very small so they are sending me to a another doctor for another scan to double check and make sure their measurements weren’t off. I’m nervous because looking things up on google now has me feeling like my baby will have some type of brain development is issues if not already. Has anyone gone through this before?