Shadow on babies heart

Ruscell • Im 27. I have 3 beautiful kids and a step son. I am on my 4th baby finger crossed. 8th pregnancy.
In 19w 5d and the ultrasound shows a small shadow on her heart. Im going to be refered to a specialist and was told not to stress about it but i cant help but be worried. Anyone else deal with this and if so how did it turn out?