I was told my baby may have an enlarged heart: Advice?

.I had a growth scan at 37 weeks pregnant, and at my weekly appointment today, I was told they would be calling me to go to a hospital to do another ultrasound because the baby’s heart was borderline large. At my 20-week anatomy scan, it was normal; she said not to freak out that some ultrasound techs don’t do a good job, so she wants one done at a hospital. Has this happened to anyone? I am freaking out!