Racial disparities in preterm birth in USA: a biosensor of physical and social environmental exposures

• Published in: Archives of disease in childhood 2019-10, Vol.104 (10), p.931-935
• Main Authors: Burris, Heather H, Lorch, Scott A, Kirpalani, Haresh, Pursley, DeWayne M, Elovitz, Michal A, Clougherty, Jane E
• Format: Article
• Language: English
• Subjects: Acids; African Americans; Anemia; Animal models; Biosensors; Birth; Birth weight; Continental Population Groups; Developed countries; Educational Status; Environmental Exposure - adverse effects; Environmental health; Evidence-based medicine; Female; Folic acid; Health disparities; Health Status Disparities; Hispanic Americans; Humans; Infant mortality; Infant, Newborn; Infants; Iron; Iron deficiency; Leading article; Metabolites; Micronutrients; Nitrogen dioxide; Nutrient deficiency; Observational studies; Outdoor air quality; Pediatrics; Phenotypes; Phthalates; Pregnancy; Premature birth; Premature Birth - ethnology; Premature Birth - prevention & control; preterm birth; Public health; Public Policy; Race; race and health; Race Factors; Racial differences; Racial Segregation; social determinants; Social Environment; Supplements; United States - epidemiology; Vitamin B; Vitamin D; Vitamin deficiency; Whites; Womens health; Young Children
• ISSN: 0003-9888; 1468-2044
• DOI: 10.1136/archdischild-2018-316486

Introduction The infant mortality rate in USA exceeds that of most other developed nations, ranking 26th among Organisation for Economic Co-operation and Development countries.1 Non-Hispanic black infants in USA die more than twice as often as non-Hispanic white infants (11.4 vs 4.9 per 1000 live births).2 This disparity reflects disparities in preterm birth (PTB) rates, since two-thirds of infant mortality occurs in preterm infants.3 The PTB rate is 52% higher for black (13.8%) than white (9.0%) women. Iron deficiency and anaemia, which are more common among African-Americans,19 20 has likewise been associated with PTB in observational studies,21 but randomised controlled trials of iron supplementation have been disappointing.22 In a recent study, over 15 000 women were randomised to one of three interventions: folic acid alone, folic acid with iron and multiple micronutrients.23 While the last group had a significant decrease in spontaneous PTB, there was no difference in the folic acid with iron group compared with the folic acid only group. Phthalate metabolite levels can vary by race/ethnicity due microenvironmental39 as well as macroenvironmental exposures.40 In a prospective, nested case-control study (n=130 cases, 352 controls) in Boston, women with higher levels of several phthalate metabolites had higher odds of spontaneous PTB (ORs 1.22–1.67 per ln-unit increase).38 While evidence that physical environmental exposures contribute to PTB risk is accumulating, it is not yet clear what proportion of racial disparities in PTB is attributable to differences in the physical environment. Better causal inference modelling, including mediation may also facilitate a better understanding as to the relative contributions of multiple exposures.58 Multilevel modelling can also clarify the relative contribution of neighbourhood factors versus individual-level factors.59 60 Additionally, collaborating with translational scientists and toxicologists to identify biological pathways by which toxic chemicals could lead to a specific PTB phenotype in animal models or in vitro can help to clarify whether as association is more likely to be truly causal.