Births to Parents with Asian Origins in the United States, 1992–2012

Despite a remarkable increase in Asian births in the U.S., studies on their birth outcomes have been lacking. We investigated outcomes of births to Asian parents and biracial Asian/White parents in the U.S. From the U.S. birth data (1992–2012), we selected singleton births to Korean, Chinese, Japanese, Filipino, Asian Indian, and Vietnamese. These births were divided into three groups; births to White mother/Asian father, Asian mother/White father, and births to the both ethnic Asian parents. We compared birth outcomes of these 18 subgroups to those of the White mother/White father group. Mean birthweights of births to the Asian parents were significantly lower, ranging 18 g to 295 g less than to the White parents. Compared to the rates of low birthweight (LBW) (4.6%) and preterm birth (PTB) (8.5%) in births to the White parents, births to Filipino parents had the highest rates of LBW (8.0%) and PTB (11.3%), respectively, and births to Korean parents had the lowest rates of both LBW (3.7%) and PTB (5.5%). This pattern of outcomes had changed little with adjustments of maternal sociodemographic and health factors. This observation was similarly noted also in births to the biracial parents, but the impact of paternal or maternal race on birth outcome was different by race/ethnicity. Compared to births to White parents, birth outcomes from the Asian parents or biracial Asian/White parents differed depending on the ethnic origin of Asian parents. The race/ethnicity was the strongest factor for this difference while other parental characteristics hardly explained this difference.

Neonatal and Infant Mortality in Korea, Japan, and the U.S.: Effect of Birth Weight Distribution and Birth Weight-Specific Mortality Rates

Difference in crude neonatal and infant mortality rates (NMR and IMR) among different countries is due to the differences in its two determinants: birth weight distribution (BWD) and birth weight-specific mortality rates (BW-SMRs). We aimed to determine impact of BWD and BW-SMRs on differences in crude NMR and IMR among Korea, Japan, and the U.S. Our study used the live birth data of the period 2009 through 2010. Crude NMR/IMR are the lowest in Japan, 1.1/2.1, compared to 1.8/3.2, in Korea, and 4.1/6.2, in the U.S., respectively. Japanese had the best BW-SMRs of all birth weight groups compared to the Koreans and the U.S. The U.S. BWD was unfavorable with very low birth weight (< 1,500 g) rate of 1.4%, compared to 0.6% in Korea, and 0.8% in Japan. If Koreans and Japanese had the same BWD as in the U.S., their crude NMR/IMR would be 3.9/6.1 for the Koreans and 1.5/2.5 for the Japanese. If both Koreans and Japanese had the same BW-SMRs as in the U.S., the crude NMR/IMR would be 2.0/3.8 for the Koreans and 2.7/5.0 for the Japanese. In conclusion, compared to the U.S., lower crude NMR or IMR in Japan is mainly attributable to its better BW-SMRs. Koreans had lower crude NMR and IMR, primarily from its favorable BWD. Comparing crude NMR or IMR among different countries should include further exploration of its two determinants, BW-SMRs reflecting medical care, and BWD reflecting socio-demographic conditions.

Birth Outcomes of Koreans by Birthplace of Infants and Their Mothers, the United States versus Korea, 1995-2004

The acculturation effect of immigrant women on birth outcomes varies by race. We examined birth outcomes of three groups of births for the period 1995-2004, USA births to the USA-born Korean mothers, USA births to the non-USA-born Korean mothers, and births in Korea. In singleton USA births to both Korean parents, average birth weight was 3,294 g for the USA-born Korean mothers and 3,323 g for the non-USA-born Korean mothers. However, this difference was not significant, once controlled for other maternal sociodemographic, obstetric and medical factors. Low birth weight and prematurity prevalence were not different by maternal nativity between these two singleton groups. Average birth weight of all births including multiplets in Korea was 3,270 g, compared to 3,297 g for all USA-born infants including multiplets and births either to both or one Korean parents. This difference might have reflected a significantly lower educational attainment of mothers in Korea compared to Korean mothers in the USA. Low birth weight rate was consistently lower in infants born in Korea compared to the USA-born, but this difference became less, 4.2% and 4.6% respectively by 2004. These observations suggest that in the USA acculturation effect of Korean immigrants on birth outcomes is negligible.