# Maternal Nativity, Race, and Ethnicity and Infant Mortality in the US

## TL;DR

US-born mothers have higher infant mortality rates than non-US-born mothers, especially for full-term births, with disparities seen across racial and ethnic groups.

## Contribution

This study reveals that maternal nativity is linked to infant mortality disparities, particularly among full-term births, across multiple racial and ethnic groups in the US.

## Key findings

- US-born mothers had higher infant mortality rates than non-US-born mothers (5.4 vs 4.0 deaths per 1000 births).
- The disparity was most pronounced for full-term births, with an adjusted odds ratio of 1.58.
- Sudden unexpected infant death was a major cause of mortality among full-term births for US-born mothers.

## Abstract

In the US, is maternal nativity or race and ethnicity associated with infant mortality, and do these associations vary by gestational age?

In this cohort study of more than 25 million births from 2016 to 2022, infant mortality rates were higher among US-born birthing individuals compared with non–US-born birthing individuals. This disparity was accounted for by full-term births among those who were Black, Hispanic, White and multiracial.

These findings suggest that maternal nativity status is associated with infant mortality across racial and ethnic groups, highlighting the need for investigation into the underlying factors contributing to these disparities, particularly among full-term births.

This cohort study examines the associations among the birthing parent’s nativity status and race and infant mortality in the US and assesses whether these associations differ by gestational age.

Racial disparities in infant mortality in the US are well-established, but the associations among maternal nativity status, race, ethnicity, and infant mortality remain understudied.

To examine the associations among maternal nativity status and infant mortality by maternal race and ethnicity in the US, and to assess whether these associations differ by gestational age.

This retrospective, population-based cohort study used linked birth and infant death records for all recorded US live births from 2016 to 2022. Births to foreign residents and those with missing data on maternal nativity, race, ethnicity, or gestational age were excluded.

Maternal nativity status (US born vs non–US born).

The primary outcome was infant mortality, defined as death within 364 days of life. Logistic regression was used to quantify the association between maternal nativity status and infant mortality, adjusting for maternal and infant characteristics. Leading causes of death among preterm (<37 weeks) and full-term (≥37 weeks) births were examined by nativity. Full-term births were further analyzed by race and ethnicity.

Among 25 981 364 births, 20 141 084 (77.5%) were to US-born individuals, and 5 840 280 (22.5%) were to non–US-born individuals (mean [SD] age, 29.1 [5.8] years). US-born individuals had a higher infant mortality rate than non–US-born individuals (5.4 vs 4.0 deaths per 1000 births; adjusted odds ratio [aOR], 1.34; 95% CI, 1.32-1.36). This disparity was primarily seen for full-term births (aOR, 1.58; 95% CI, 1.54-1.63) and was less apparent among preterm births. Among full-term births, higher rates of infant mortality in US-born individuals were found among those identifying as Black (aOR, 1.55; 95% CI, 1.45-1.66), Hispanic (aOR, 1.39; 95% CI, 1.32-1.45), White (aOR, 1.45; 95% CI, 1.35-1.55), and more than 1 race (aOR, 1.33; 95% CI, 1.04-1.69). Leading causes of death differed by nativity and race and ethnicity, with US-born individuals having higher odds of sudden unexpected infant death compared with their non–US-born counterparts among full-term births (aOR, 2.90; 95% CI, 2.74-3.07).

This population-based cohort study found that US-born individuals had significantly higher odds of infant mortality compared with non–US-born individuals, particularly among full-term births and among those self-identifying as Black, Hispanic, White, or more than 1 race. Sudden unexpected infant death was a major contributor to these disparities. Investigation into the underlying factors contributing to these disparities is needed.