COVID-19 pandemic-era changes in non-SUID infant mortality in the United States

Abstract Introduction The COVID-19 pandemic has been associated with increases in sudden unexpected infant death (SUID), but less is known about other causes of infant mortality (referred to here as non-SUID). We examined pandemic-era changes in non-SUID mortality by gestational age, age at death and cause of death. Methods We conducted a nationwide cohort study using Centers for Disease Control and Prevention National Center for Health Statistics data for US births from 2016 to 2021, including deaths in 2022. We focused on non-SUID mortality by excluding International Classification of Diseases, 10th Revision codes for SUID. Pandemic-era births were those between April 2020 and December 2021. Interrupted time series analyses were used to determine prepandemic mortality trends and assess whether there were level or trend changes associated with the COVID-19 pandemic. Results Overall non-SUID infant mortality rates consistently trended downwards with no pandemic-associated change. However, stratified analyses showed that trends differed by subgroup. While mortality rates among preterm infants continued their prepandemic declines, rates among full-term infants reversed their prepandemic declines. Postneonatal deaths similarly reversed their prepandemic decline, with statistically significant increases during the pandemic. Estimated monthly mortality rates for infants born at the end of the study period were 8.7% and 16.5% higher than expected for term births and postneonatal deaths, respectively. In contrast, the decline in early neonatal mortality rates became more pronounced during the pandemic, with a 7.2% reduction in observed versus expected monthly mortality rates. Infection-related mortality initially declined but later returned to prepandemic levels. Rates of mortality due to external causes increased during the pandemic. Mortality rates for perinatal conditions and congenital malformations continued their prepandemic declines. Conclusions Declining overall non-SUID infant mortality masked pandemic-era increases among full-term infants, postneonatal infants and deaths from external causes. These findings support prioritising preventive paediatric care and injury-prevention strategies during future public health emergencies.