Hispanic and black infants born in this country enjoy a BW advantage if their mothers were not U.S.-born. The authors used two datasets on three cohorts of infants to explore this phenomenon. The trans-generational birth file contains BW and demographic data on 267,604 infants born in Illinois in 1989-91 as well as data on those infants' mothers (born in Illinois in 1956-76). Mexican-Americans (newly immigrated and established) were compared to European-Americans and African-Americans for effects of immigration across three generations. The 1985-88 Illinois birth file contains detailed ethnicity variable which made it possible to analyze separate subgroups of non-US black mothers (African and Afro-Caribbean).

5867 women of Mexican descent gave birth in Illinois in 1956-76. Infants with Mexico-born mothers weighed 67 g more than those with US-born mothers(p<.01). Over the succeeding generation, this BW gap closed partially: female infants born to these same girls after they reached adulthood (1989-91) still showed a 48 g difference in mean BW (p<.01). This finding was next compared across ethnic groups. BW of European-American infants varied the least (25 g) with nativity of the mother (US vs. foreign born) while African-American varied the most (204 g). The BW advantage with an immigrant mother diminished over the succeeding generation in white and black infants as it did for Hispanics.

Using the 1985-88 files, we found women born in sub-Saharan Africa, Mexico and Europe delivered babies with nearly identical BW distributions. Infants of Black mothers born in the West Hemisphere but outside the US had a BW distribution midway between those of African-born and US-born black mothers.

Conclusion: The phenomenon of higher BW in the immigrant generation was confirmed in the Illinois populations of African and Mexican descent, but was minimal or absent for European immigrants. Babies born to 1st generation African immigrant women in 1985-88 had a BW distribution nearly indistinguishable from 1st generation European and Mexican immigrants.