Mortality Trends in Preterm Infants with Birth Weight Less Than 500 Grams in the United States.

This study aimed to determine the temporal trends and racial differences in the infant mortality rate (IMR) in preterm infants with birth weight <500 g in the United States from 2005 through 2022.This was a retrospective cross-sectional study of data from the CDC's Wide-ranging Online Data for Epidemiologic Research. Infants with gestational age (GA) 22 to 28 weeks, with birth weight of <500 g, and deaths up to 1 year of age were included. IMR was calculated as deaths per 1,000 live births for each GA and year, and further stratified by maternal race. We evaluated trends with Joinpoint regression and IMR trends were reported using average annual percentage change (AAPC) with 95% confidence intervals (CI). The fetuses-at-risk approach was used to examine racial/ethnic differences in IMR.During the study period, 39,511 out of 50,855 infants born at 22 to 28 weeks GA with birth weight <500 g died within the first year (overall IMR 776.93 per 1,000). The IMR was inversely related to gestational age. The overall IMR decreased significantly from 817.48 to 714.51 (AAPC of -0.8%; CI, -1.0, -0.6) and in all the three racial/ethnic groups. As per the fetuses-at-risk approach, non-Hispanic Black (NHB) infants had the highest IMR of 1.33 per 1,000 fetuses-at-risk compared with 0.39 for non-Hispanic White (NHW) and 0.46 for Hispanic infants (p < 0.01).The IMR in extremely preterm infants weighing <500 g at birth decreased significantly, overall, and in all racial/ethnic groups. However, significant racial/ethnic differences persist. · Infant mortality rate decreased significantly in preterm infants with birth weight <500 g.. · The IMR decreased significantly in the three racial/ethnic groups studied.. · The IMR was significantly higher in non-Hispanic Black infants..