Objective: This study attempts to explain lower VLBWR and LBWR in Asian-Americans compared to Non-Hispanic Whites (NHW) by examining factors associated with VLBWR and LBWR.

Method: The study population was derived from the U.S. Birth Cohorts of 1992-94. The study population was divided into two groups, singleton infants born to Chinese, Japanese, or Korean mothers, the CJK group(n=127,771), and singleton infants born to Non-Hispanic White mothers, the NHW group (n=7,246,447).

Results: VLBWR and LBWR of the CJK group were significantly lower than the rates of the NHW group (5.8 and 43.7 per 1,000 live births vs. 7.5 and 46.9 per 1,000 live births, p<.001). A majority of CJK infants were born to the foreign-born mothers (83.9%), compared to NHW infants (4.7%). Infants born to the U.S.-born CJK mothers had significantly higher VLBWR and LBWR (6.9 and 56.0 per 1,000), compared to infants born to the foreign-born CJK mothers (5.5 and 41.2 per 1,000). Infants born to the U.S.-born NHW mothers had significantly higher LBWR (47.0 per 1,000 live births) compared to the foreign-born (42.8 per 1,000), but this difference was not significantly different for VLBWR. In general, the foreign-born mothers tended to have more favorable sociodemographic status than the U.S.-born mothers in both ethnic groups. When the analysis was restricted to infants born to low-risk mothers(maternal age 20-39 years, education 12 years or more, married, adequate prenatal care and live birth order 2-4), CJK infants had higher VLBWR and LBWR(5.2 and 34.9 per 1,000 live births) than NHW infants (3.9 and 22.3 per 1,000 live births). For LBWR, this difference persisted for both foreign born and U.S. born mothers (foreign-born: 23.1 in NHW vs. 33.3 per 1,000 in CJK; the U.S.-born: 22.2 vs. 42.5 per 1,000, both p<0.001).

Conclusions: These results suggest that 1) among infants born to mothers with low risk factors for very low and low birth weight, Asian American infants have higher very low and low birth weight rates than Non-hispanic White infants and 2) the lower very low or low birth weight rate in Asian American infants than in Non-Hispanic White infants is attributable to higher proportion of foreign-born Asian American mothers with favorable sociodemographic factors.