Isis Arnesen, of Boston, kisses her 14-week-old daughter, Lucia, after the baby went to the bathroom after her mother noticed a sign from the child Friday at a park in Watertown, Mass. The diaper-free movement is gaining momentum.

Erinn Klatt holds her son, Dominic Klatt, 1, over the toilet, Thursday at their home in Sutton, Mass. Dominic is a product of a diaper-free movement founded on the belief that babies are born with an instinctive ability to signal when they need to go to the bathroom.

Sutton, Mass. ? Thirteen-month-old Dominic Klatt stopped banging the furniture in the verandah, looked at his mother and clasped his right hand around his left wrist to signal that he needed to go to the bathroom.

His mother took the diaper-less tot to a tree in the yard, held him in a squatting position and made a gentle hissing sound – prompting the infant to relieve himself on cue before he rushed back to play.

Dominic is a product of a growing “diaper-free” movement founded on the belief that babies are born with an instinctive ability to signal when they have to answer nature’s call. Parents who practice the so-called “elimination communication” learn to read their children’s body language to help them recognize the need, and they mimic the sounds that a child associates with the bathroom.

Erinn Klatt began toilet training her son at birth and said he has not wet his bed at night since he was 6 months old.

“The nice part is … really getting the majority of poops in the toilet versus having to clean that,” Klatt said. “I don’t have to wake up at night and change diapers or have wet sheets anywhere. That’s really nice.

“And being able to travel without a big, bloated diaper bag is terrific.”

Some parents and toilet training experts are skeptical.

“They teach them from birth? Oh, my God!” said 40-year-old Lisa Bolcato, as she held her 5-month-old daughter, Rose, at a park on Boston Common. “When you’re getting two hours of sleeps between feedings, I don’t think that you have the time to do it. You just make sure that your child’s healthy and happy and well-fed.”

Still, the practice is common in many parts of rural Africa and Asia where parents cannot afford diapers.

In the United States, many of the parents are stay-at-home-moms, but there are also working mothers. Some meet in online groups, at homes and in public parks to share experiences and cheer each others’ efforts.

Experts at the Child Study Center at the University of Oklahoma Health Sciences Center say children younger than 12 months have no control over bladder or bowel movements and little control for 6 months after that.

But some parents begin going diaper-free at birth, and the infants can initiate bowel movements on cue as young as 3 to 4 months, said Elizabeth Parise, spokeswoman of DiaperFreeBaby.org, a network of free support groups promoting the practice.

And unlike some methods of toilet training, there are no rewards or punishment associated with it.

Dr. Mark Wolraich, professor of pediatrics and director of the Child Study Center, said the practice essentially conditions young children to go to the bathroom at predictable times or show clear signs when they must go.

“To be truly toilet-trained, the child has to be able to have the sensation that they need to go, be able to interpret that sensation and be able to then tell the parent and take some action,” said Wolraich, who is also editor of the American Academy of Pediatrics’ book on toilet training.

“And that’s different from reading the subtle signs that the child is making when they have to go to the bathroom.”

Parents attempt the early training to forge closer ties with their infants, to reduce the environmental impact associated with diapers and to avoid skin irritation caused by a wet diaper, Parise said.

Others were inspired by observing the practice while traveling abroad.

The practice also enables parents to get insight into an infant’s development because more accidents occur if a child falls sick or enters a new phase such as learning to crawl, walk or talk.

This is because an infant may be too distracted by illness or efforts to master a new skill to communicate the need to go to the bathroom, said Melinda Rothstein, an MIT business school graduate who co-founded DiaperFreeBaby.org.

She says finding a supportive day-care center is the biggest challenge for parents who choose not to use diapers. Other problems include finding tiny underwear for diaper-free infants.

Isis Arnesen, 33, of Boston, has a 14-week-old daughter, Lucia, who is diaper-free. She said it can be awkward to explain the process to people, such as when she helped Lucia relieve herself in a sink at a public restroom.

“Sometimes I don’t know what’s gonna happen and it doesn’t work, and sometimes I feel a little embarrassed,” Arnesen said. “It makes her happy though, right? She smiles, she’s happy.”