High rates of neonatal polycythemia and hyperbilirubinemia during the first phase of COVID-19 pandemic in Italy: a single-center experience.

In our third-level Neonatal Unit in Northern Italy, we recorded a high rate of neonatal hyperbilirubinemia requiring phototherapy in March-November 2020, during the first phase of COVID-19 pandemic, compared to the previous year (198/1348, 14.2%, vs 141/1432, 9.8%, p = 0.0004). Supposing it could be the result of neonatal polycythemia, we evaluated capillary hematocrit (Hct) and the rate of hyperbilirubinemia in all newborns ≥36 weeks gestational age born in December 2020. Out of 73 neonates, 37 had Hct ≥65% (50.7%). However, as capillary blood samples may overestimate Hct by 5-15%, even downsizing all values by 15%, Hct was still ≥65% in 9/73 neonates (12.3%), much higher than 0.4-5% prevalence of polycythemia reported in healthy newborns. All those newborns were singleton and healthy, with no clinical signs of hyperviscosity and no underlying factors predisposing to polycythemia. Out of 73 newborns, 13 (17.8%) developed hyperbilirubinemia requiring phototherapy. Their mean Hct value was 66.3 ± 8.2%. Since hyperbilirubinemia is common in the offspring of women with SARS-CoV-2 infection and we recorded increased rates of neonatal hyperbilirubinemia in the first phase of COVID-19 pandemic, it could be hypothesized that even asymptomatic Sars-CoV2 infection during pregnancy might cause placental vascular malperfusion, eliciting polycythemia in the fetus as a compensatory response, that could be the link between COVID-19 in the mothers and hyperbilirubinemia in the newborns.