A report released by WHO earlier this year found conflicting evidence that the benefit to mother and child ceased above 10 percent.
"This 10 to 15 percent target was just kind of created through expert consensus. A lot of things in policy come out this way, but we had some techniques and better data available now than in the past," said Alex Haynes, a surgeon at Massachusetts General Hospital.
But the study also shows that the benefits of using the procedure flatten out as the rate exceeds 19 percent. In the United States, where the rate approached one-third of all births in 2013, leading health officials have called for a reduction in the practice. While rates vary by geography and hospital, studies have raised questions about whether C-sections are being used unnecessarily.
Despite the high rate of C-sections, the United States continues to have a terrible maternal mortality rate -- near the bottom of the world's richest countries, according to data recently released by the World Health Organization.
The JAMA study also suggests that some countries don't have enough access to C-sections -- or at least the level of care that comes with the procedure.
"The sort of paradoxical message of this paper here is there are a lot of places with not enough access to comprehensive obstetrical care like a C-section," Haynes said.
An editorial published along with the study agreed that it isn't a matter of any particular country reaching a single, optimal C-section rate. That one number won't be the same for any country, or any hospital or group of mothers and babies. Instead, those authors suggested a meeting of medical and scientific leaders to better define how the practice can be properly used to improve mothers' and infants' health.