Pericardial effusion experiences?

I’m a nervous wreck for in one week I get to see baby’s heart and if any fluid accumulated in the last month. Has anyone had any experience with this? At my anatomy scan I had 1.9mm and then about a month later 2.6mm. The report says trivial and psychological in nature. I just haven’t been able to turn my brain off and there is absolutely no information online about this.