Socioeconomic Risk Factors for Extreme Preterm Birth in Hawai'i.

Socioeconomic status and race/ethnicity are widely understood to be determinants of adverse birth outcomes, but studies have been limited by lack of income data in health records and aggregation of racial groups in reporting. This study aims to evaluate the relationship of socioeconomic status to extreme preterm birth outcomes in the diverse ethnic population of Hawai'i. Statistical analyses were conducted on Hawai'i birth records 2004-2013 linked to American Community Survey data by maternal residence. Community-level income demographics were stratified into wealth quintiles and stratum specific odds ratios were calculated for extreme preterm birth with analysis focused on the highest and lowest income-quintiles. The overall rates of extreme preterm birth were similar in high vs low-income communities, yet the individual risk factors were significantly different. In low-income communities, increased risk of extreme preterm birth was identified for women less than 20 years old and Black women, while in high-income communities, Native Hawaiian and Black women were at increased risk. Previous preterm birth, birth of a first child and cumulative maternal medical conditions were significant risk factors at all income levels. For Native Hawaiian women, the significant overall increased risk of extreme preterm birth persists in high-income communities but not in low-income communities, suggesting that increased risks previously attributed to Native Hawaiian race/ethnicity may be partially explained by low socioeconomic status.