SARS-CoV-2 perinatal transmission and neonatal outcomes across four different waves of COVID-19 pandemic: A nationwide prospective cohort study from the Italian Society of Neonatology.

Objectives: To describe how SARS-CoV-2 infection at the time of delivery affected maternal and neonatal outcomes across four major waves of the COVID-19 pandemic in Italy.

Methods: This is a large, prospective, nationwide cohort study collecting maternal and neonatal data in case of maternal peripartum SARS-CoV-2 infection between February 2020 and March 2022. Data were stratified across the four observed pandemic waves.

Results: Among 5201 COVID-19-positive mothers, the risk of being symptomatic at delivery was significantly higher in the first and third waves (20.8-20.8%) than in the second and fourth (13.2-12.2%). Among their 5284 neonates, the risk of prematurity (gestational age <37 weeks) was significantly higher in the first and third waves (15.6-12.5%). The risk of intrauterine transmission was always very low, while the risk of postnatal transmission during rooming-in was higher and peaked at 4.5% during the fourth wave. A total of 80% of positive neonates were asymptomatic.

Conclusion: The risk of adverse maternal and neonatal outcomes was significantly higher during the first and third waves, dominated by unsequenced variants and the Delta variant, respectively. Postnatal transmission accounted for most neonatal infections and was more frequent during the Omicron period. However, the paucity of symptoms in infected neonates should lead us not to separate the dyad.