Isolated echogenic intracardiac focus.

Has anyone been told this after their 20 week ultrasound? Everything else looks great but my dr said she wants to have another look in 4-6 weeks. She also said not to worry but this is my 4th pregnancy and the first time anything has been 100% 'routine'. So it's been hard not to worry. My ultrasound isn't for almost 3 more weeks.