A new study published in the journal BMJ reviewed 195 different hospitals’ price tags when it came to delivering babies and found that the varying degree of expense is so wide that some California medical centers charge women 11 times more than others.

The researchers looked at some 110,000 births and Caesarean sections, finding that the lowest charge was $3,296 and the highest was $37,227 — a trend that is mirrored throughout the U.S. health care system. Even when the researchers adjusted the hospital expenses to focus on patients with similar backgrounds, ages, and time spent in the hospital, they still found that the differences in what people were paying were significant. The study states in its conclusion: “These results indicate that charges and discounted prices for two common, relatively homogeneous diagnosis groups — uncomplicated vaginal delivery and Caesarean section — vary widely between hospitals and are not well explained by observable patient or hospital characteristics.”

Overall, the study found that California hospitals were more likely to charge more if they were located in areas with a high cost of living, treated a sicker population, or were for-profit institutions. But this didn’t account for the majority of differences. It appears the wide variety of prices is linked to the fact that hospitals often charge whatever they want to.

“Health care pricing is kind of like the Wild West,” Dr. Renee Y. Hsia, the lead author of the study and an associate professor of emergency medicine at University California San Francisco, told Kaiser Health News. “There is no real system of health care pricing. The ‘system’ is that hospitals are allowed to charge whatever they want and whatever they feel they merit.” In a study completed earlier, Hsia had reviewed the different prices for appendectomy in California. She found that they ranged from $1,500 to $182,955. “It’s not an exception, it’s the rule in the United States,” she said.

Hospitals previously didn’t give out information about fees and procedure costs in order to maintain a competitive advantage. Last year, the federal Centers for Medicare and Medicaid Services released a report that identified the differences in costs for 100 medical procedures, and found there was a stark difference between what hospitals were charging patients. “Currently, consumers don’t know what a hospital is charging them or their insurance company for a given procedure, like a knee replacement, or how much of a price difference there is at different hospitals, even within the same city,” Health and Human Services Secretary Kathleen Sebelius told USA Today. “This data and new data centers will help fill that gap.” The report found that a joint replacement in Oklahoma cost $5,300 in comparison to the same procedure done in California for $223,000. The data spurred a law that requires hospitals to provide patients with information about how much procedures cost, as part of the Affordable Care Act.

“Most perniciously, uninsured people are the ones who usually pay the highest prices for their hospital care,” Ron Pollack, executive director of Families USA, a consumer advocacy group, said in a statement, according to USA Today. “It is absurd — and, indeed, unconscionable — that the people least capable of paying for their hospital care bear the largest, and often unaffordable, cost burdens.”