Thin septum in heart?

Dee

Had my 20 week scan today and everything was normal but the tech kept coming back to his heart. Then he calmly says “uh the septum in his heart is thinner than it should be so you’ll have to get this checked”..... now I’m panicking!

Has anybody experienced this? I have a follow up ultrasound at 28 weeks to check and see if it was just a developmental delay . His heart is pumping fine but I’m still worried!