C-sections are the most common surgery performed in the U.S., and researchers estimate that almost half the procedures are unnecessary.

The best way to protect yourself from an unnecessary C-section is to choose a hospital with a good track record when it comes to avoiding them. But the data you need to make an informed choice is not always available.

A Consumer Reports analysis of more than 1,300 hospitals found that C-section rates for low-risk deliveries among U.S. hospitals vary dramatically, even in the same communities and among similar institutions, and that in most hospitals the rates are above national targets.

But Consumer Reports does not have C-section rates for more than half the estimated 3,000 U.S. hospitals that deliver babies. That’s because hospitals are not required to publicly report that information, and many choose not to.

The hospitals without publicly available C-section rates include 28 with more than 5,000 births.

A spokesman for Memorial Hermann Greater Heights Hospital in Houston—one of three nonreporting hospitals with the most births—said that the hospital does track and review its C-section rates internally and that rates were on track to be on target by 2020. The other two hospitals, NewYork-Presbyterian Hospital in New York City and Northside Hospital in Atlanta, did not respond to requests for a comment.

“You have to give credit to the hospitals that report their data, even the hospitals that are lower performers,” says Leah Binder, chief executive officer of The Leapfrog Group, the nonprofit organization that collects and reports the data in most of the country. “It’s the hospitals that don’t report that you have to wonder about.” Binder notes that hospitals do not have to pay The Leapfrog Group when they report data.

Some hospitals, including Tampa General Hospital and Yale-New Haven Hospital, told us they don't report to The Leapfrog Group because they thought that information was publicly available through the Joint Commission, a hospital accrediting organization. But although the Joint Commission does collect C-section rates for hospitals with more than 300 births each year that use its accreditation service, it does not make that information public. (Tampa Bay General Hospital, when asked why they don't report,  shared its C-section rates with us: 25.3 percent.)

Erica Mobley, The Leapfrog Group’s director of communications and development, says hospitals can report the same data they send to The Joint Commission.   

If your hospital is not included in our ratings, ask why. And ask your doctor or midwife about the hospital’s rates. A hospital’s C-section rate for low-risk deliveries for first-time moms should be below 23.9 percent. If your provider doesn't tell you, consider going to another hospital.  

Large Hospitals That Don’t Report C-Section Rates

The hospitals below all reported delivering at least 5,000 babies in 2015 but did not share their C-section rates with The Leapfrog Group. (Hospitals are listed alphabetically, within states.)