Marie Mongan, an educator who helped popularize a childbirth-preparation technique known as hypnobirthing, which has been used by British royals Kate Middleton and Meghan Markle, actress Jessica Alba and hundreds of thousands of other women to achieve a gentler birth experience, has died at 86.

Her death, on June 17, 2019, in Bow, N.H., was not widely reported at the time. The cause was complications from Sjogren’s syndrome, an autoimmune disease, said her daughter Maura Geddes.

Hypnosis has been used for pain management for several hundred years, but its application in obstetrics is a more recent development — following the arrival of the modern natural birth movement in the 1930s, with the notion that the pain of childbirth could be alleviated if an expectant mother was unafraid and relaxed.

Hypnobirthing, which uses hypnosis to induce even greater calm during labor, remained in a state of prolonged infancy until the late 1980s, when Mrs. Mongan became certified in hypnotherapy. She established an institute that conducted classes, wrote a book on the practice, and became one of its chief exponents in the United States.

“We are taking the birthing world by calm,” Mrs. Mongan declared in 1999.

Mrs. Mongan’s hypnobirthing program, which consists of in-person classes and audio recordings for pregnant women and their partners, includes breathing exercises, visualizations, music and positive affirmations that train women to drop into a deeply meditative, relaxed state when prompted with cues.

The program culminates at childbirth, when the woman channels her preparation to enter into a hyper-focused state of mind, akin to daydreaming, aiming to progress through labor peacefully, without pain medication or anesthesia.

Mrs. Mongan was influenced by the writings of Grantly Dick-Read, a British obstetrician credited with sparking the modern natural birth movement. Using his theories, she gave birth to her children naturally in the 1950s and early ’60s.

“And this,” she explained to the Philadelphia Inquirer years later, “was when women were totally anesthetized and the baby was delivered with forceps. I brought myself to such a totally relaxed state, without an aspirin or anything.”

After a career that included stints as a teacher, women’s college dean and secretarial school founder, she became certified in hypnotherapy in 1988. The next year, she created her first hypnobirthing program for her pregnant daughter, Maura. Her 1992 book, now titled “HypnoBirthing: The Mongan Method,” is in its fourth edition and has been translated into at least four languages.

“Picture yourself gently resting on a bed of strawberry-colored mist that is about a foot and a half high,” she wrote in the latest edition of the book. “Picture the soft red mist as a mist of natural relaxation flowing through and around your body. Continue to relax until it seems that your body is almost weightless and seems to meld into the mist.”

In 2000, she started the HypnoBirthing Institute (now HypnoBirthing International), which certifies doulas, midwives, doctors and laypeople to act as hypnobirthing educators.

Although Mrs. Mongan believed everyone could be taught to bring themselves into an intensely relaxed state and insisted hypnobirthing could dramatically reduce — if not eliminate — pain during childbirth, the science surrounding the technique is inconclusive.

Anette Werner, a Danish midwifery researcher who studies hypnosis and childbirth, said randomized control trials, including her own, showed that while women who had training in self-hypnosis did not have lower pain levels or lower epidural use during labor, several of the trials found hypnosis had a positive impact on the childbirth experience.

“Mothers were also less likely to request C-section for future deliveries because hypnosis lessened their fear of childbirth,” she wrote in an email.

At first dismissed by traditional doctors as a fringe idea, hypnobirthing has become a more mainstream birthing technique, practiced through a variety of methods.

Mrs. Mongan’s program is taught at nearly a dozen hospital programs across the United States, and HypnoBirthing International, the practice’s oldest and largest accreditation body, estimated that 250,000 couples take the online and in-person course globally each year.

“Our philosophy is to teach a woman to know and trust her body; her body will know how to do it,” Mrs. Mongan told the Chicago Tribune in 2002. “It’s more than a walk in a meadow or along the shore. It’s bringing them to the deepest state. It isn’t always pain free, but it is easier and more comfortable and more spiritual.”

Marie Madeline Flanagan, nicknamed “Mickey,” was born in San Diego on Feb. 1, 1933, and grew up mostly in Franklin, N.H. Her mother was a seamstress, and her father was a Navy chief petty officer.

In 1954, she married Gerald Bilodeau, a high school classmate. That same year, she graduated from what is now Plymouth State University in New Hampshire, where she also received a master’s degree in education in 1971. She worked as an English teacher at her old high school in Franklin.

She recalled that when she became pregnant with her first child, in 1955, she refused to accept “folklore” about pain as a rite of passage. Even her mother, she said, “always told me how horrific childbirth was.”

“I just couldn’t believe we had a Creator with such a warped sense of humor that they would make us sexual beings and then make childbirth so agonizing,” she told the Boston Globe.

She said she dove into literature on natural childbirth and gave birth four times during the next six years “with absolutely no pain whatsoever.”

She and her husband divorced in 1966, and she married Eugene Mongan in 1970. He died in 2013. In addition to Geddes, of Bow, survivors include her three other children, Wayne Flanagan of Sunapee, N.H., Brian Kelly of Chichester, N.H., and Shawn Mongan of Epsom, N.H.; three stepchildren, Michelle Shoemaker of Weare, N.H., Steve Mongan of San Francisco and Nancy Kelley of Citrus Heights, Calif.; 17 grandchildren; and four great-grandchildren.

Following the birth of her children, Mrs. Mongan continued her career in education. In 1965, she became dean of the now-defunct Pierce College for Women in Concord, N.H., and in 1973 opened the Thomas Secretarial School in Concord. The school, which she named after a friend, shuttered in the early 2000s.

After becoming certified in hypnotherapy, she began helping clients quit smoking, lose weight and overcome their fear of flying. When Geddes announced her pregnancy in 1989, Mrs. Mongan decided to piece together her studies on relaxation, natural birth and hypnosis to create a program, which she taught in one of the classrooms of her secretarial school.

“I had a wonderful birth,” Geddes said. “Music played, the lights were dim, and she kept saying, ‘Relax, breathe, quiet your mind.’ The nurses were all coming in because they would not believe how calm and relaxed I was, and the centimeters were just going up.”

One of the nurses in attendance, who was pregnant and impressed with the techniques, asked Mrs. Mongan for an appointment to help with her birth. Over the next few years, as her work spread by word of mouth, Mrs. Mongan began training instructors and teaching expectant couples, wrote her book and set up a website.

In 1999, NBC’s “Dateline” ran a segment on a Florida obstetrician who used hypnosis on his patients. The next day, MSNBC wrote an accompanying story mentioning Mrs. Mongan’s role in the practice, linking to her website. She began fielding questions from all over the world.

“We received almost 5,000 calls and emails over the next few weeks,” she wrote in the latest edition of her book. “HypnoBirthing took on a life of its own, and in a very short time, it took over my life as well.”

Still, she added, doctors expressed skepticism and regarded the calm births they witnessed as “flukes.”

“In looking back now,” she wrote, “I must admit — the acceptance of HypnoBirthing didn’t come the way I thought it would. It was a very steep uphill climb. A few times a doctor would inquire, ‘What did you say this is?’ ”

But Mrs. Mongan saw the practice gain popularity and acceptance. She spent the last 20 years of her life traveling around the world, teaching her program and advocating for the rights of mothers to give birth without excessive medical intervention.

“My dream is that every woman will be able to bring a baby into the world calmly and gently,” she told the Globe.