In the United States (US), disparities in perinatal and neonatal outcomes by race and ethnicity have been well documented. Disparities occur within single healthcare centers, within states, within national populations, and over time.1,2 In recent years, there is a growing recognition that these disparities reflect inequities because they arise as a result of unjust differential treatment, of individuals and entire communities, due to characteristics that reflect societally created groupings.2, 3, 4 However, there is also a rich body of literature that documents disparities in perinatal and neonatal outcomes by nativity, another variable important to an individual's identity and how they are situated within US society.

A person's nativity indicates where they were born, and is defined by country of origin.5 However, researchers also use nativity to dichotomize people as native-born (i.e. born in the country being studied) or foreign-born (i.e. born outside the country under analysis).6,7 Thus, nativity can represent granular data regarding a specific country or as a global indicator of immigrant status. Similar to race and ethnicity, nativity is a variable that is not within an individual's control. While nativity can unite people and form the basis of community ties, it has also been used as a sociodemographic characteristic to aggregate individuals and regulate them through laws and policies.8 Currently, immigrants represent nearly 14% of the total US population. The fact that immigrants have a slightly higher fertility rate than US-born birthing people9 indicates the importance of studying birth outcomes within this population.

We review the relationship between a birthing person's nativity status and their risk for three adverse outcomes which are important for population health and we focus on the US experience. We evaluate the existing literature on low birthweight (LBW; birthweight < 2500 grams), preterm birth (PTB; gestational age< 37 weeks) and infant mortality (death in the first year of life). Although small-for-gestational age (SGA) (i.e. birthweight less than 10th percentile for gestational age) is a related outcome, we did not include it in this review given worldwide variability in how SGA is defined and ongoing conversations about whether some of these definitions are problematic and may obscure racial disparities in fetal growth (see Belfort et al. review in this issue).

We use the words “women” or “mother” when these terms were used by the original literature cited. However, this paper is meant to be inclusive of all people who birth infants, regardless of the birthing person's gender. Similarly, as the predominance of papers we reviewed used the word “Hispanic,” we will also use this term. However, we recognize that some people prefer the use of terms such as Latinx, Latine, or Latino/a. Although the terms are not technically interchangeable,10 this paper is meant to be inclusive of all who identify with any of these terms. Finally, because current immigration policies are deeply rooted in the 1965 Hart-Celler Act, which abolished national origin quotas and simultaneously capped the number of resident visas which could be issued,11 we focused exclusively on research published after 1970. Our aims were to summarize epidemiologic findings, identify overarching themes, and provide clear recommendations for researchers who are committed to elimination of health disparities.