The headline to this Times story from Tuesday concerning a recent CDC report on U.S. infant mortality in comparative perspective summarizes the main finding: because 1 in 8 U.S. births were preterm, compared to 1 in 18 in Ireland or Finland, and preterm babies have higher mortality rates, the excess rate of premature births accounts for a third of the U.S. infant mortality rate.
The report points out that preterm babies in the U.S. actually have lower mortality rates than they do elsewhere. But the problem is that preterm mortality is enough higher than full-term mortality for the difference in the carrying-to-term propensity to more than offset this advantage.
The Times article discusses some reasons why rates of being born premature are higher in the U.S., which is apparently the crucial issue. The lead author of the CDC study was quoted as saying, “Fifteen or 20 years ago, if a woman had high blood pressure or diabetes, she would be put in the hospital, and they would try to wait it out. It was called expectant management. Now I think there’s more of a tendency to take the baby out early if there’s any question at all.”
This sounds like poor adult (mother's) health driving poor child health. There were other potential reasons cited too, however.