Do you have mothers here whose children had or have pericardial effusi…

Do you have mothers here whose children had or have pericardial effusion (fluid in the heart cavity)? We discovered it during pregnancy, they said it might resolve but it hasn't decreased. After childbirth, we will undergo cardiological examination and further monitoring, treatment. I am interested in how serious this is, how scary it is, and what treatments were used and if it has passed?