Are there residual socioeconomic disparities in IUGR?

In an earlier section, I reviewed the evidence concerning factors that may mediate the socioeconomic disparities in IUGR incidence. Leading candidates for quantitatively important (from a population perspective) factors include cigarette smoking (both frequency and severity), low gestational weight gain (presumably due to low energy intake), and short stature. Alcohol, drugs of abuse, and maternal work and physical activity may explain a small, additional portion of the disparity. But can the entire socioeconomic gradient in IUGR be explained by the above-mentioned risk factors? This is an important question for both perinatal epidemiologists and public health policy makers. Unfortunately, the answer is unknown. Most research in this area has tended to focus on one or two factors at a time. Few have adequately measured all of these potentially mediating variables, and most have had insufficient sample sizes to do so. Thus it is unknown whether any residual socioeconomic disparities remain after accounting (controlling) for known, or strongly suspected, mediating variables. This is a promising area for future research that may not only uncover new etiologic determinants of IUGR, but also help reduce its high incidence among the socially disadvantaged.