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Am J Perinatol
DOI: 10.1055/a-2593-0505
Original Article

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

Patrycja Tesmer
1   Valley Children's Pediatric Residency Program, Madera, California
,
Fredrick Dapaah-Siakwan 
1   Valley Children's Pediatric Residency Program, Madera, California
2   Department of Neonatology, Valley Children's Healthcare, Madera, California
› Author Affiliations Funding None.
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Abstract

Objective

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.

Study Design

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.

Results

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).

Conclusion

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.

Key Points

  • 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.

Keywords

extremely preterm infants - birth weight less than 500 g - infant mortality rate - gestational age 22 to 28 weeks - racial differences - fetuses-at-risk - births-based approach - trends

Note

This study was presented as a poster at the 2024 American Academy of Pediatrics National Conference and Exhibition on September 27, 2024 in Orlando, Florida.


Data Statement

All data used for this study are publicly available from the CDC WONDER Web site ( https://wonder.cdc.gov/natality.html ).


Authors' Contributions

P.T.: methodology, investigation, data curation, statistical analysis, and writing—original draft preparation. F.D.-S.: conceptualization, methodology, statistical analysis, investigation, supervision, validation, and writing—reviewing and editing.




Publication History

Received: 21 November 2024

Accepted: 22 April 2025

Accepted Manuscript online:
23 April 2025

Article published online:
12 May 2025

© 2025. Thieme. All rights reserved.

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