That appears to be changing. Spurred in part by the new research, medical groups such as the American Congress of Obstetricians and Gynecologists are working on a consumer-friendly database that will tap clinical information from electronic medical records. That effort could take another three to five years.
Monday's study comes amid a national effort to improve medical quality, and hopefully reduce costs, by using data to compare care providers. Those lagging usually try to improve. Research-based approaches have been used successfully in other industries.
The study did not identify hospitals.
Led by Dr. Laurent Glance, a professor of anesthesiology at the University of Rochester medical school in New York, researchers analyzed billing data for a national sample of more than 750,000 deliveries in 2010.
About 4 million women give birth every year in the U.S., and having a baby is the single most common reason for a hospital stay. While pregnancy-related deaths are rare, complications are about as common as for heart surgery.
The study did not look at outcomes for babies. It grouped hospitals into three quality categories — low, average, and high — according to their rates of complications for the mother.
To allow an apples-to-apples comparison, the researchers adjusted for differences in the health status of patients served by the hospitals.
At the low-quality hospitals, an average of nearly 23 percent of the women delivering vaginally experienced a major complication, compared with about 10 percent of the women at high-quality facilities. The rate of complications at average-quality hospitals was 15 percent.
Unusual bleeding and tearing were the most common complications of vaginal birth.
For cesarean birth, the quality gap was wider.
At the low-quality hospitals, an average of nearly 21 percent of the women undergoing a cesarean delivery experienced a major complication, compared with a rate of less than 5 percent at the high-quality hospitals. The rate of cesarean complications at average-quality hospitals was nearly 9 percent.
Unusual bleeding and infection were the most common complications of cesarean birth.
"The bottom line is that there's a lot of variation," said Glance. "It's an opportunity to go out there and try to make things better."
Speaking for doctors who deliver babies, the American Congress of Obstetricians and Gynecologists said much more work needs to be done to make such data useful for individuals.
Dr. Barbara Levy, the group's health policy expert, called the study "very preliminary."