Mediators of ethnic-associated differences in infant birth weight

To examine whether ethnic differences in low birth weight babies of low-income women may be explained in part by group differences in prenatal health behaviors and psychosocial factors.

A prospective, survey of 1,071 low-income, primiparous African-American and Mexican-origin women was conducted in Los Angeles County, California. In face-to-face interviews, data were obtained on substance use, prenatal stress, social support, attitudes toward pregnancy, initiation of prenatal care, and medical risk. Medical chart data were abstracted regarding medical risk factors and labor, delivery, and neonatal data. Interview data were linked with birth outcome data retrieved from maternal medical records. Structural equation modeling was used to test a hypothesized model in which differences in birth weight were expected to be mediated by ethnic differences in substance use, psychosocial factors, and medical risk.

As expected, African-American women delivered babies of earlier gestational age and lower birth weight than did women of Mexican origin. Direct predictors of low birth weight were use of drugs and cigarettes, prenatal stress, and positive attitudes toward pregnancy; together, these factors accounted for the observed ethnic differences in birth weight.

These data contribute to our understanding of the factors that may account for ethnic-associated differences in low birth weight.