July 22, 2014 — Even though economic and health disparities persist, more low-income women are giving birth to infants with healthier birthweights than 25 years ago, the Washington Post reports.
A recent study by Princeton University economist Janet Currie and colleagues compared birthweights of infants born to women who were black, unmarried high school dropouts -- typically demographic indicators of being low-income -- with those of women who were white, married college graduates -- a group that tends to include individuals with higher incomes. According to the Post, many researchers use demographic information, such as race, marital status and education, as proxies for income information, which is not included on birth certificates.
The researchers found that one-sixth of infants born in 1989 to the lower-income group weighed under five-and-a-half pounds -- which doctors consider to be the lower bound of a healthy birthweight -- compared with one out of 32 infants born to the higher-income group.
About 20 years later, one-eighth of the infants born to the lower-income group had unhealthy birthweights, while the rate was largely unchanged for the higher-income group. The authors also found the same trends when they looked at the data after removing the factor of race.
Factors Influencing Birthweight
Other researchers have found that government policies such as food stamps, nutritional counseling and efforts to expand access to care have had a significant positive effect on birthweight. Further, other policy efforts and social trends -- such as regulations limiting pollution and auto emissions, and a decline in smoking rates -- also have played a role.
Meanwhile, studies have found several factors that continue to contribute to lower-income women giving birth to underweight infants at a higher rate, including pollution, stress and violence.
For example, researchers have found that women with annual incomes below $25,000 are two-and-a-half times more likely to be survivors of domestic violence. Further, women who have been sent to a hospital as the result of domestic violence tend to have infants who weigh five ounces less on average than women who have not (Goldfarb, Washington Post, 7/20).