A step in another direction: looking for maternal genetic and environmental effects on racial differences in birth weight.

To advance research on birth weight differences between black and white infants, it may be useful to study maternal effects. These effects present a set of risk factors that are largely unrelated to those that are presently under investigation and fail to explain the gap in birth weight; empirical findings suggest their involvement. Although maternal effects can be environmental, as illustrated by recent findings, genetic effects could be important as well because gene frequencies are known to differ across the "racial" groups as studied by birth weight researchers, and maternal genes can exert a causal effect on birth weight.