In a study performed on an entirely African American population, infants born to moms who used a pre-natal multivitamin during gestation demonstrated improved birth weight and fetal growth rate than those infants whose mothers did not consume a pre-natal vitamin during gestation, according to the Annals of Epidemiology.
Source: Periconceptional Multivitamin Use and Infant Birth Weight Disparities
I think all expecting mothers should use a high quality pre-natal multivitamin to fill any gaps in their diet. The gains fair outweigh the costs in this situation regardless of race.