Comparison of Neonatal and Infant Mortality Rates between Infants Born in South Korea and Those Born in the United States

ABSTRACT

PURPOSE: The neonatal (NMR) or infant mortality rate (IMR) in South Korea is lower than that in the United States. We aimed to investigate the contributing factors to this difference in mortality rates. METHODS: The study populations consisted of five groups, namely group A, comprising live births in South Korea during 2009-2011 (n=1,383,806), and groups B (live births to Korean parents, n=107,309), C (Caucasian births, n=31,588,183), D (African-origin, n=4,381,664), and E (all live births, n=49,384,187) comprising various US live births during 2000-2011. Maternal characteristics, birth outcomes, and mortality rates in these five groups were compared according to birth weight (BW) and gestational age (GA). RESULTS: Maternal characteristics such as BW distribution and very low and low BW rates among infants in South Korea and those in the United States were quite similar. Both rates were significantly lower among the Korean live births than among Caucasian and African-origin live births in the United States. However, the mortality rates of these small birth weight groups were significantly higher in the Korean infants born in South Korea than in those born in the United States, or in Caucasian and African-origin infants born in the United States. Similar results were noted when analyzed according to gestational age. CONCLUSIONS: The NMR or IMR in South Korea is lower than that in the United States, primarily due to the overwhelming favorable BW and GA distribution, despite the lower BW- and GA-specific survival rates in the live births in South Korea than in the United States.