Optimal birth weight and term mortality risk differ among different ethnic groups in the US

Among European countries, optimal birth weight at which the mortality is minimal is shown to be different by country. We investigated this difference examining one geopolitical population, the U.S. term live births, born to the five groups of the same ethnic parents; White, Black, Hispanic, North Asian, and South Asian. North Asians and South Asians had more favorable maternal factors for birth weight. Yet, Whites had the highest mean birth weight and South Asians, the lowest. However, neonatal mortality rate in Whites was 0.78 per 1,000 live births, significantly higher than 0.36 and 0.72 per 1,000 live births in North Asians and South Asians, respectively. Other maternal factors hardly explained this ethnic disparity in birth weight or mortality. Optimal birth weight was greatest in Whites (3,890 g), and least in South Asians (3,491 g). However, neonatal mortality at optimal birth weight was significantly lower in North Asians. Adjustment of maternal factors except parental ethnicity changed little of this difference. Optimal birth weight and its mortality differ by ethnicity. On planning the best birth outcome in a population, one should consider the variable mortality risks by ethnicity.