"In large part we [the U.S.] include every child born alive," said Sachs.
Sachs thought abortion rates also play in to the numbers.
"About 20 percent of the children who die in the U.S. do so from birth defects," said Sachs. "In a country that has a liberal abortion policy, those children will die in abortion -- some countries even allow third-trimester abortions so their rates [of infant mortality] are going to be lower," he said.
But maternal mortality, which is the measure that cut the U.S. rankings the most, is more complicated to report.
"I think there is a real difference in terms of maternal mortality, but no one knows what it is," said Sachs.
For instance, Sachs said a woman who dies of an ectopic pregnancy may or may not be counted as a maternal death.
"But I do think the maternal mortality is a little bit higher in the United States," said Sachs.
Sachs estimated that the high numbers of uninsured women, including illegal immigrants with "scant prenatal care" are driving up the U.S. maternal mortality rate.
"Those women are at risk," said Sachs.
Sachs and Katz agreed that insuring that every pregnant woman has access to health care and prenatal care would help the U.S. improve mortality rates and other birth complications. Katz pointed out that currently 40 million people in this country do not have health insurance -- or more than 13 percent of the population .
But Katz said that going without health insurance alone is not an explanation for bad pregnancy outcomes in the U.S.
While the high obesity rates in the U.S., rates of older mothers and other health factors play a minor role in the bad health outcomes for mothers in the United States, Katz said, "The major question I would ask is, 'Why do African American populations have worse results than the white population?'"
Powers said Save the Children's research has also found that pregnant "minority" women who seek medical care do not end up getting the same quality of care as pregnant women "in the majority."
Katz said currently it's hard to measure which social, economic, and health care realities are influencing which poor outcomes.
"The United States is a very complicated country -- we have a tremendous number of diverse populations, of diverse economic groups," said Katz. "It's impossible to answer the question 'why?'"
"Once you create good access to health care whatever else that is adverse can be dealt with," said Katz.