NPPB and persistent fetal circulation syndrome: The relative risk of death was also high in PPHN patients infected with SARS-CoV-2 who had steroids (RR 1.87, 95% CI 0.74–4.74), NRDS as a cause of PPHN (RR 1.78, 95% CI 0.69–4.52), sildenafil to treat PPHN (RR 1.70, 95% 0.83–3.46), IVIG to treat COVID-19 (RR 1.67, 95% 0.65–4.29), and high NT-proBNP (RR 1.63, 95% CI 0.79–3.33).