“The most dangerous of wealthy nations for a child to be born into.” That’s how global health researchers characterized the United States in a January 2018 report published in Health Affairs that sounded alarm bells about the country’s high infant mortality rate. U.S. babies, they found, were three times as likely to die of premature birth and 2.3 times as likely to die of sudden infant death syndrome than infants in comparably rich countries.

Anne Driscoll, a demographer and statistician at the Centers for Diseases Control and Prevention’s National Center for Health Statistics, has been analyzing possible causes for years and has previously looked at maternal age, the rural-urban divide and other factors. Driscoll and her colleague Danielle Ely teamed up in a report released Wednesday to delve into infant mortality in two of the country’s most impoverished regions: Appalachia and the Mississippi River Delta region. The former includes 26 million people in 420 counties stretching from New York to Georgia, and the latter includes 9.8 million people in 252 counties in eight states in the South. Both have been hit hard by the epidemic of people addicted to opioid painkillers.

Driscoll and Ely chose these areas because they are clearly defined (they are part of federal-state partnerships that encourage business development, infrastructure upgrades and otherwise try to jump-start the areas’ economies), and because they suspected, based on other studies about health outcomes there, that the regions might disproportionately suffer from infant mortality.

They were right.

In the study published Wednesday, they looked at the characteristics of mothers of the nearly 400,000 babies born in 2017 in the Delta and Appalachia regions and how their children fared. They found that women in the Delta were most likely to be teenagers, unmarried and not have a college degree — characteristics associated with poor infant outcomes. The infants born in the Delta were most likely to be born preterm, have a low birth weight, and die within the first 12 months. The infant mortality rate in the Delta was 8.17 deaths per 1,000 births, with a rate of 6.82 in Appalachia and 5.67 in the rest of the United States.

Driscoll said in an interview that if these regions were excluded from an analysis of the United States, you would see an overall lowering of the U.S. infant mortality rate — but only “a little lower, not massively lower.” Some of their previous work, for instance, has shown that maternal age is also a big factor with babies of older women as well as younger women having worse outcomes.

Driscoll said the analysis is just “step one” of their work in trying to figure out what is leading to the country’s high infant mortality rates and many findings raise more questions than answers. For example, they found there wasn’t a big difference between white women in the Delta and white women in Appalachia. The same goes for black women in the Delta and in Appalachia. But when they looked at Hispanic women who gave birth in the Delta area, the outcomes were significantly better than those in Appalachia. In fact, they were more similar to that of the rest of the United States. She said that needs further investigation. It could have to do with age, better health characteristics, education or something else entirely.

“This is something we want to explore more,” she said. “Is there a protective effect or something different going on? We don’t know yet, but we think it’s very important to find out."

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