DISCUSION
Secondary pleural effusion is usually caused by generalized fluid retention in non-immune hydrops (8). The causes of this pathology include cardiovascular and idiopathic diseases, genetic, metabolic and hematological disorders, infections, structural abnormalities and chest tumors (9). To the best of our knowledge there where only reported three confirmed SARS-CoV-2 infections during pregnancy complicated by hydrops fetalis (2-4). In each case, the SARS-CoV-2 infection occurred in a different trimester of pregnancy and all of them were complicated by intrauterine fetal death. Two patients were infected before diagnosis (2,4) and one was in active infection (3). Whereas, a PCR SARS-CoV-2 test was performed on a fetal lung biopsy and was positive (3). An active infection from the TORCH group was ruled out in these patients. Cytogenetic analysis revealed a normal karyotype in every case. Moreover, histologic examination of the placenta or fetal tissues was performed. Shende et al. reported fibrin deposition around the villi, where the syncytiotrophoblast was lysed, and extensive leukocyte infiltration suggesting inflammation (2). A similar picture was obtained in the studies by Rodrigues et al. and Popescu et al. In both cases a postmortem examination showed systemic thrombosis with thrombi in the small and medium vessels. Recent blood clots were identified in fetal circulation (3,4). In the study by Popescu et al. the pregnant was Rh negative so, Rh immune globulin was given, as in our case. An attempt was made to perform a thoracocentesis and insert a percutaneous in utero thoracoamniotic shunt (4). The limitations of our case are no SARS-CoV-2 tests performed in placenta, amniotic fluid, and fetal tissues. After birth the rapid antigen test was performed, which was negative. Therefore only the clinical symptoms and the exclusion of other possibilities, i.e. TORCH infections, genetic disorders, Rh immunization and the proliferative process may indicate vertical transmission of the virus. This case may constitute the basis for further studies, as the pleural effusion is a serious emergency for a newborn.