Requested follow up scan

Hi ladies— I had my 20 week scan last Friday and the doctor reviewed the results with me and said everything looked great.

I just got a call from my doctor office asking for a follow up Ultrasound. What gives? I’m so confused because they said everything looked ok but I can’t help but think they need me to come back in because everything doesn’t look so great.

Has this happened to anyone else? Trying not to freak out...