Microbiological features and follow-up of neonates born to mothers with covid-19

Background: Literature evaluating the effect of SARS-CoV-2 infection in exposed newborns during pregnancy is still scarce. Although a 3% rate of perinatal transmission has been described, there is not enough evidence of viral transmission in biological samples through microbiological techniques. Our aim is to describe perinatal transmission in newborns exposed to SARS-CoV-2 during pregnancy and their follow up. Methods: The study period is from March 15 to November 30, 2020. Exposed newborns of SARS-CoV-2 infected mothers (with microbiologically confirmed COVID-19 disease during pregnancy or delivery) were included at 13 hospitals in Spain. Demographic, clinical and microbiological data were collected. Biological samples including nasopharyngeal swab, blood, urine, and meconium from newborns and blood, placenta, and breast milk from mothers were collected for reverse transcription polymerase chain reaction (RT-PCR) analysis. Results: 282 exposed to SARS-CoV-2 neonates were recruited;130 cases during the first wave (March 15-July 31) and 152 during the second one (August 1- November 30). The prematurity birth-rate was 20% and 13% respectively. Overall, eleven newborns were positive for RT-PCR in nasopharyngeal swab, eight of them during the first 24-48 hours after birth. Three of them presented viral load in urine sample and another three in meconium sample. Only one RT-PCR was positive in maternal blood samples (1/115) and placenta (1/81). All newborns blood samples collected at delivery were negative for RT-PCR (0/70). There was no viral load either in breast milk samples (0/79). Placental immuno-histochemistry performed for SARS-CoV-2 showed no virus (0/16). Two newborn death were described none of them related to SARS-CoV-2. Those newborns exposed to SARS-CoV-2 were asymptomatic and with normal weight and psychomotor development at 6-months follow-up. Conclusion: Intrauterine SARS-CoV-2 transmission seems unlikely, describing a 3.9% rate of neonatal infection after delivery. A high rate of prematurity is described, mostly during the first wave. SARS-CoV-2 can be detected by RT-PCR in urine and meconium of neonates with positive nasopharyngeal RT-PCR, whereas it has not been detected in any newborn blood. The detection in maternal blood and placenta was anecdotal and it was not detected in breast milk samples. Except for the complications derived from prematurity, exposed newborns evolution was satisfactory.