Heterogeneity within Asian subgroups: a comparison of birthweight between infants of US and non-US born Asian Indian and Chinese mothers.

OBJECTIVES

Birthweight distributions and proportions of low birthweight (LBW) are commonly used to assess the health of populations. However, the "population" is difficult to define due to differences by race, socioeconomic status, age distribution, and cultural identity. This study analyzes birth outcomes in two Asian subgroups to examine variation within the Asian population.

METHODS

Analysis of the 1998-2003 National Center for Health Statistics' natality file for 293,211 singleton births in Asian Indian and Chinese mothers compared birthweight distributions, mean birthweights, proportions of very low birthweight (VLBW) and moderately low birthweight (MLBW) infants, and the influence of maternal nativity on these outcomes. A multiple logistic regression analysis, stratified by maternal nativity, was done to control for established confounders of maternal age, marital status, education, and parity.

RESULTS

Maternal characteristics and birthweight distributions varied by race subgroup and nativity. Infants of Asian Indian mothers had a lower mean birthweight and higher proportions of VLBW and MLBW than Chinese. After controlling for differences in maternal characteristics, infants of US born Asian Indian mothers were more likely to be VLBW (AOR 1.87, 95% CI: 1.27-2.75) or MLBW (AOR 1.59, 1.39-1.82) than infants of US born Chinese mothers. Similarly, infants of non-US born Asian Indian mothers were more likely to be VLBW (AOR 2.13, 2.06-2.21) or MLBW (AOR 2.26, 2.18-2.35) then infants of non-US born Chinese mothers.

CONCLUSIONS

Our study demonstrates variation in birth outcomes by maternal race and nativity in two Asian subgroups. The heterogeneity within a single commonly used "population" is likely not limited to these two Asian subgroups, but is probably applicable to many populations in the United States. Analyses should try to account for these differences to ensure a more accurate representation of various populations in the US. The difficulty of defining a population by race adds to the complexity of examining disparities in birth outcomes.