Frédérick Leboyer advocated for childbirth techniques that placed the newborn baby first. (Eamonn McCabe/For the Guardian)

It was somewhere around his 9,000th delivery that Frédérick Leboyer began questioning his methods and those of his colleagues — obstetricians who worked in noisy, brightly lit operating rooms and concluded each birth by picking the infant up by its heels and smacking it on the bottom.

The ensuing wail was, according to tradition, the sign of a happy, healthy, newly breathing baby.

For Mr. Leboyer, who died May 25 at 98, it began to seem like the low point in an act that was no less painful than a stabbing.

“Yes, hell exists,” he wrote in “Birth Without Violence,” a 1974 prose poem that served as his medical cri de coeur. “It is not a fairy tale. One indeed burns there. This hell is not at the end of life. It is here. At the beginning. … This is birth. This is the torture, the Calvary.”

Mr. Leboyer, a French physician whose hatred of the medical establishment led him to stop using the title “doctor” and eventually close his private practice in Paris, was described variously as a quack, a radical revolutionary and a spiritual guru. A pilgrimage to India and a subsequent foray into psychoanalysis opened his eyes to the horrors of childbirth, he said, leading him to advocate for birthing methods that were gentler on newborns, if sometimes less convenient for the doctors who helped bring them into the world.

To help “transform births into nativities,” as he once put it, he called for dim lighting in the delivery room and a minimum of noise and conversation. Slapping was forbidden, and the umbilical cord — providing the child air for so many months — was typically not cut until it stopped beating. The baby would be placed on the mother’s belly, gently massaged with bare hands, and eventually taken to a warm bath designed to imitate the amniotic fluid.

Mr. Leboyer shot to fame after he outlined his methods in “Birth Without Violence,” which became a bestseller in France and was subsequently translated into more than a dozen languages, and in an accompanying 21-minute film set to the music of a Japanese flute.

“A newborn and his mother need a loving artist’s attention, not the impersonal manipulation of a highly trained engineer,” he told the New York Times in 1974, chastising his peers for taking a sterile, technology-driven approach to childbirth.

For the most part, the medical community chastised Mr. Leboyer in return. Newborns should always be handled with surgical gloves, said critics, and bright lights were necessary to determine the infant’s color, an early health indicator.

Yet Mr. Leboyer’s methods gained traction with mothers, if not doctors, and — in part because of their insistence — soon began appearing in hospitals around the United States and Europe. His teachings led in part to the development and popularization of the waterbirth technique, through acolyte Michel Odent.

“I don’t think there are many people spanking babies or shining bright lights on them today,” John T. Queenan, an official at the American College of Obstetrics and Gynecology, told the Times in 1989. “But if anyone told me they were doing Leboyer as originally described,” bath and all, “I’d be very surprised.”

Perhaps most controversially, Mr. Leboyer insisted that his methods were central not only to the happiness of the infant, but also to the happiness of the full-grown adult. The trauma of childbirth, he said, often while recounting the story of his own birth, was never fully forgotten.

Mr. Leboyer was born Alfred Lazare Levy to a Jewish family in Paris on Nov. 1, 1918. Through psychoanalysis, he claimed to recall that his mother, a painter, “suffered terribly” when she gave birth to him — with forceps, without anesthesia and three weeks late. His father was in the wine and diamond trades, and died when Alfred was about 17.

Alfred Levy graduated from the University of Paris, and during World War II he moved with his younger brother to Megève, a ski resort across the border from Vens. The siblings changed their names to Leboyer — a French alteration of Levy — to avoid being captured by the occupying Nazis.

His brother, Maurice Lévy-Leboyer, became a prominent economic historian and died in 2014. Frédérick Leboyer died at his home in Vens, Switzerland, several weeks after suffering a stroke, said a nephew, Antoine Leboyer of Geneva.

He is also survived by his wife of 12 years, Mieko Yoshimura of Vens. He said he regretted having no children.

In addition to “Birth Without Violence,” Mr. Leboyer wrote poetry and books including “Loving Hands” (1976), which taught mothers how to massage their newborns, and “Inner Beauty, Inner Light” (1978), which taught yoga for pregnant women.

Following his trip to India, Mr. Leboyer said he seemed to see a kind of “inner light” in each person. When the Times contributor Steven Englund visited his Parisian home in 1974, Mr. Leboyer displayed prints showing Renaissance-era depictions of the baby Jesus. “See how the light shines from the Infant Christ’s face?” he said. “There is no reason why that cannot happen for all babies. But first we must stop treating them as mere squalling digestive tracts.”