Despite an ever widening income gap in America, a surprising “newborn equality” continues to emerge as health measures improve for poor mothers and their babies. A review of economic research published in Science on Thursday describes the counterintuitive findings.

"That was really surprising to us," Anna Aizer, an associate professor of economics at Brown University, said in a press statement.

Aizer and a colleague at the National Bureau of Economic Research analyzed studies from the past several years to examine how “maternal disadvantage” affects newborn health. Traditionally, women from lower socioeconomic strata suffer greater exposure to harmful environmental and social stressors, including greater exposure to toxic pollutants as well as violence and stress. Such women often lack quality prenatal care and nutrition, and are also more likely to engage in unhealthy behaviors during pregnancy.

Yet the rate of newborns with low birthweight has continued to fall among the economically disadvantaged, even as that rate has remained constant for wealthier women during the past generation. In an attempt to explain the data, Aizer says improved public policy and programming has apparently “broken the cycle of poverty” throughout much of America, despite President Reagan’s famous 1980s declaration of defeat in the War on Poverty.

That such improvements come from improved public health policy “seems like the obvious answer” to Azier, however. "We know a lot more about improving health at birth than we did 20 years ago and there are more policies now that are trying to do just that."

Among changes since the 1980s, the researchers emphasize a dramatic reduction in environmental pollution affecting prenatal health, as well as improved services for poor women including the Supplemental Feeding Program for Women, Infants, and Children. More recently during the Obama administration, the U.S. government has provided improved prenatal services with the Nurse Family Partnership program, as well. Additionally, the federal government has improved postnatal care for women and newborns, with early education and a greater social safety net for the poor.

However, Aizer says policymakers shouldn’t draw the wrong conclusions from the study, given that differing interventions may work best for different demographics.

"I think it would be a mistake in policy if the additional resources provided during the prenatal period are not followed up with additional resources postnatal," Aizer said. "From a policy perspective, you really do need to know where to put your money.”

Source: Aizer A, Currie J. The intergenerational transmission of inequality: Maternal disadvantage and health at birth. Science. 2014.