Several 2010 studies on the labors of first-time mothers disproved Dr. Friedman’s curve with two discoveries. First, active labor didn’t begin at 4 centimeters, but at 6 centimeters. Second, the average dilation per hour was 1 centimeter, not 3 centimeters. “In Dr. Friedman’s time, if you were dilating at about 1 centimeter per hour, that was too slow,” Ms. Dekker said. “You would be considered to have failure to progress or abnormal labor. Today, research is finding very different averages for what is normal.”

According to Dr. Friedman’s study, active labor began sooner, and took less time, than it actually does today. This error has produced countless unnecessary C-sections. Doctors should have waited; instead they operated. Dr. Friedman’s curve lives on, despite having been disproved — it appeared in medical textbooks as recently as 2010. “We have generations of obstetric providers educated in that paradigm that have to change their practice,” Ms. Dekker said. “We don’t know how many people are still using the old-fashion information.” Hospitals with exorbitantly high cesarean rates may still be using the Friedman curve, while those committed to limiting unwarranted surgery have ditched it.

How One Hospital Cut C-sections in Half

C-sections dwindled at Beth Israel Deaconess Medical Center because the staff decided that they should. “When you move toward a decrease, it has to be valued, not just by the people leading the project, but by the obstetricians, nurses and midwives,” Dr. Golen said. Beth Israel is forensic in its use of the newest and best evidence. Providers don’t order C-sections as early as they did in the past. Rather than surgery, they first offer laboring women “supportive care,” hewing to the recommendation of the American College of Obstetricians and Gynecologists. “Supportive measures really just allow the patient more time,” Dr. Golen said. “Just by making the active stage start at 6 centimeters, it allows patients so much more time to reap the benefits of the supportive care that we can provide.”

She explained that measuring success, and creating a bit of competition by publicly praising doctors who lowered their rates, aided their quest. This recognition comes at department meetings, during rounds and on social media. “People are really proud when their name appears on the list of people who have met or exceeded the goal,” she said.

The School Supply Cure

What worked for Beth Israel hasn’t worked for all hospitals, at least not yet. Margie Bridges, a nurse at Overlake Medical Center in Bellevue, Wash., said her team has fought to lessen cesareans for years. “Our C-section rate is one of the best of the worst. And it’s not for lack of effort,” she said. Overlake’s cesarean rate has hovered around 30 percent since 2014, even after many of the measures that succeeded at Beth Israel were applied. Overlake discarded the Friedman curve years ago, it uses the new data and offers supportive care, and it sets goals and celebrates successes. But the rates didn’t budge.

Which brings up a successful practice used elsewhere that relies on an item commonly found in a home goods store. In January, the Team Birth Project, conceived in Boston’s Ariadne labs, began a study of this item in four community hospitals across the country, including Overlake. Dr. Shah directs the program, and he believes that it will limit cesareans with a simple tool — a large, white, dry erase board placed in a visible spot in every labor and delivery room. Overlake hangs its behind the bathroom doors.

What’s on the board? First, the name of every labor and delivery team member — birthing woman, obstetrician, nurse, doula and partner. Dr. Bettina Paek, a perinatologist at EvergreenHealth, another pilot hospital, in Kirkland, Wash., said, “This puts mom at the center of the care team.”