Hello! As per your description of the USG findings, of mild cardiomegaly & left renal (kidney) caliectasis implies a congenital fetal defect. Mild cardiomegaly means a slight increase in the size of the heart, this may be an isolated congenital defect or may be part of renal congenital abnormalities like in this case caliectasis meaning dilatation of the renal calyces (urinary outflow track). You may have consultation with an eminent pediatrician. We will require to wait until the birth, as at present the problems does not seem serious. So, you need not worry much. It would most probably recover spontaneously, the heart size should be spontaneously reduced & dilatation of unilateral calyces may be managed with surgery, nephroplassty, if not spontaneously recovered. Thanks & take care of yourselves!