As major surgeries, C-sections also use more medical resources and pose a higher risk of complication to both women and infants, resulting in more care overall.
Groups behind Monday's Truven study argued for payment reforms to incentivize natural childbirth for most women.
"We need to pay physicians and hospitals in ways that reward them for eliminating early elective deliveries, reducing unnecessary C-sections and preventing complications of childbirth," said Suzanne Delbanco of Catalyst for Payment Reform, a nonprofit employer coalition, in a statement.
"Maternity care is yet another example of how our current healthcare payment systems can actually penalize healthcare providers for delivering higher-value care," Delbanco said.
Truven estimated that U.S. spending on maternity care would drop by more than $5 billion if only 15 percent of pregnant women chose C-sections — the rate recommended by the World Health Organization — compared with the current 33 percent.
The number of C-sections has risen by half over the last decade for a variety of reasons.
Monday's study was also sponsored by Childbirth Connection, a nonprofit group that provides information about maternity care, and the Center for Healthcare Quality and Payment Reform.
—This post was last changed Wednesday at 5:25 p.m. to reflect that many factors contribute to the rising prevalence of U.S. C-sections.