20 week anatomy scan

Jen
During my scan yesterday the doc found a heart defect t and also said he is measuring three weeks behind. She said one may not relate to the other but then said she thinks this is digeorges syndrome.
I don't know what tothink or Do. Echo is set for tomorrow but they suggested I do an amnio. Any suggestions or information anyone can give me on this topic? 
Maybe my baby is just growing at a smaller rate... maybe my due date is off by a week? All these questions are rushing thru my head