Both low birthweight (<2500 g; LBW) and macrosomia (>4000 g) are considered adverse birth outcomes and are associated with later poor health conditions, yet the social determinants of macrosomia are understudied. In this study, we explore patterning of LBW, normal birthweight, and macrosomia by race/ethnicity and nativity. We examined data from all live births between 1999 and 2014 in New Jersey with a non-missing, plausible value of birthweight (n = 1,609,516). We compared the risk for LBW and macrosomia among non-Hispanic White, non-Hispanic Black, Hispanic, and non-Hispanic Asian mothers, and between the US- and native-born. For Hispanics and Asians, we also examined differences by country of origin. The racial/ethnic patterns for macrosomia mirrored those of LBW, suggesting that the factors underlying LBW shift birthweight distributions. For example, non-Hispanic White mothers had the lowest risk for LBW and the highest risk for macrosomia. Nativity patterns differed by subgroup, however, with unique risks for macrosomia among some origin groups, such as foreign-born Cubans. The racial/ethnic and nativity patterns of macrosomia do not completely mirror those of LBW, suggesting some distinct social risk factors for macrosomia. Our findings raise questions about whether and how racial/ethnic and nativity patterning in both low and excess birthweight is retained in later conditions, such as childhood obesity.
