Socioeconomic inequalities in low birth weight in the United States, the United Kingdom, Canada, and Australia

Objectives. To compare associations between socioeconomic status and low birth weight across the United States, the United Kingdom, Canada, and Australia, countries that share cultural features but differ in terms of public support and health care systems. Methods. Using nationally representative data from the United States (n = 8400), the United Kingdom (n = 12 018), Canada (n = 5350), and Australia (n = 3452) from the early 2000s,wecalculated weighted prevalence rates and adjusted odds of low birth weight by income quintile and maternal education. Results. Socioeconomic gradients in low birth weight were apparent in all 4 countries, but the magnitudes and patterns differed across countries. A clear graded association between income quintile and low birth weight was apparent in the United States. The relevant distinction in the United Kingdom appeared to be between low, middle, and high incomes, and the distinction in Canada and Australia appeared to be between mothers in the lowest income quintile and higher-income mothers. Conclusions. Socioeconomic inequalities in low birth weight were larger in the United States than the other countries, suggesting that the more generous social safety nets and health care systems in the United Kingdom, Canada, and Australia played buffering roles.