The Save the Children report, released Monday, comes just a week after publication of another report humbling to the American health-care system. That study showed that white, middle-aged Americans are far less healthy than their peers in England, despite U.S. health-care spending that is double that in England.

In the analysis of global infant mortality, Japan had the lowest newborn death rate, 1.8 per 1,000, and four countries tied for second place with 2 per 1,000 — the Czech Republic, Finland, Iceland and Norway.

Still, it's the impoverished nations that feel the full brunt of infant mortality, since they account for 99 percent of the 4 million annual deaths of babies in their first month. Only about 16,000 of those are in the United States, according to Save the Children.

The highest rates globally were in Africa and South Asia. With a newborn death rate of 65 out of 1,000 live births, Liberia ranked the worst.

In the United States, researchers noted that the population is more racially and economically diverse than many other industrialized countries, making it more challenging to provide culturally appropriate health care.

About half a million U.S. babies are born prematurely each year, data show. African-American babies are twice as likely as white infants to be premature, to have a low birth weight, and to die at birth, according to Save the Children.

The researchers also said lack of national health insurance and short maternity leaves likely contribute to the poor U.S. rankings.

Other possible factors in the U.S. include teen pregnancies and obesity rates, which both disproportionately affect African-American women and also increase risk for premature births and low birth weights.

In Utah, Bloebaum said, at least 14 percent of women who are of reproductive age lack health insurance. And that's a lot, she added, considering that there are a half-million of reproductive age. "They're probably not getting optimal care.

"We used to think that if someone had prenatal care and regular visits, everything would be great," Bloebaum said. "Now we are moving to the preconception period. Women need to be in optimal health before they are pregnant" for optimal outcomes, she said.

In past reports by Save the Children — released ahead of Mother's Day — U.S. mothers' well-being has consistently ranked far ahead of those in developing countries but poorly among industrialized nations. This year the United States tied for last place with the United Kingdom on indicators including mortality risks and contraception use.

While the gaps for infants and mothers contrast sharply with the nation's image as a world leader, Emory University health policy expert Kenneth Thorpe said the numbers are not surprising.

"Our health-care system focuses on providing high-tech services for complicated cases. We do this very well," Thorpe said. "What we do not do is provide basic primary and preventive health care services. We do not pay for these services and do not have a delivery system that is designed to provide either primary prevention, or adequately treat patients with chronic diseases."