Articles & Guides

What can we help you find?

When do babies start sucking their thumb?

Thumb sucking can be spotted as early as a child's ultrasound photo, but it's rare for babies to start sucking their thumb after 6 or 7 months. Read on to learn more about this popular habit.

Babies can start sucking their thumbs early in life.

Where is Thumbkin? Chances are babies have their adorable little thumbs in their mouths well before their grown-ups even start singing this popular nursery rhyme with them. In fact, doctors confirm that it’s not uncommon to see ultrasound images of hand- and thumb-sucking fetuses in utero.

“Babies start sucking their thumbs early on in life,” says Dr. Whitney Casares, Stanford-trained private practice pediatrician in Portland, Oregon and author of “The Working Mom Blueprint: Winning at Parenting Without Losing Yourself.” “About 90% of newborns,” she says, “show some kind of hand-sucking behavior by two hours after they are born.”

“Babies start sucking their thumbs early on in life. About 90% of newborns show some kind of hand-sucking behavior by two hours after they are born.”

— DR. WHITNEY CASARES, PEDIATRICIAN AND AUTHOR

Why? “All babies are born needing to know how to suck using their mouth and tongue,” explains Dr. Sara Siddiqui, pediatrician and clinical assistant professor in the Department of Pediatrics at NYU Langone’s Hassenfeld Children’s Hospital in New York, noting that thumb sucking can be related to the natural reflex to feed. “Thumb sucking can begin in infancy — or prior — and continue well into toddler age.”

While there is no one-size-fits-all answer to the whens and whys of thumb sucking, pediatricians do agree that thumb sucking is an absolutely normal habit for many babies and young children.

When do babies start sucking their thumb?

“Babies can find the thumb with relative ease especially in the early infant period,” Siddiqui explains. From early hand-sucking in utero to months later when babies start to clasp their hands and bring them to the mouth area at around 4 months, there is no one moment or exact range when thumb sucking may begin. Siddiqui does note, though, that it is uncommon for babies to start sucking their thumb after 6 or 7 months of age.

“Thumb sucking can begin in infancy — or prior — and continue well into toddler age.”

— DR. SARA SIDDIQUI, PEDIATRICIAN

Amy Kravetz, mom of two from Princeton, New Jersey, says that she doesn’t remember exactly when her now almost 2-year-old started but that her daughter has sucked her thumb since she was an infant. “Pretty early on, she started sucking her thumb to self-soothe — I was thrilled!” says Kravetz. “She still sucks it for comfort and when she’s tired. It hasn’t been a problem for us yet. She’s been to the dentist, who didn’t say we had to worry about her teeth. For now, I’m glad she has a way to help herself when she is upset.”

Why do babies suck their thumb?

Like Kravetz, most parents and pediatricians correlate thumb sucking with sleep, comfort and self-soothing. “Many babies suck their thumbs as a soothing mechanism when they are tired or hungry, but some suck just as a reflex,” explains Casares, noting that 80% of infants and children suck their thumbs at some point. 

Siddiqui agrees that thumb sucking is often a self-soothing technique that helps babies calm down when they are nervous or upset. “As the nervous system is developing, much sensory input is received in the mouth and tongue area, which can be soothed in babies by sucking,” she adds. She does note, though, that when infants and babies suck their thumbs when hungry, they stop when they realize they aren’t getting fed. 

That said, every baby and every thumb-sucking variation is different. Some might choose one thumb over the other. Some, as Siddiqui explains, might suck on the rest or some of the other fingers, as well. When the teething process begins, some little ones might begin placing their fingers and thumbs in their mouths for comfort although Siddiqui notes a difference between sucking one’s thumb to self soothe and simply placing fingers in the mouth to chew or try to massage the gums.

For Seth Canetti, dad of two from Lancaster, Pennsylvania, his son’s thumb-sucking habit began at 2 1/2, shortly after his baby sister was born. “We thought it was a phase that would pass once he got used to her, but 15 months later, he’s only just now starting to gradually suck his thumb less,” says Canetti. “On the bright side, he does sleep way better!”

Should parents worry if their babies do — or don’t — suck their thumb?

In general, Casares says thumb sucking isn’t a cause for concern, especially before the front teeth start to erupt from the gum line, and that most children stop sucking their thumbs without outside intervention between 2 and 4 years old. She does note that if you are noticing infections, calluses or sore thumbs — or if you suspect thumb sucking might be causing bite problems or protruding teeth — you should consult the child’s pediatrician and/or dentist.

Of course, not every child will naturally stop thumb sucking within this precise age range — and a large group of kids continue to suck their thumbs beyond 4 years old. “It’s definitely true that these kids can still grow out of this behavior,” adds Casares.

But what if your child’s prolonged thumb sucking still has you worried? “My advice would be to check in with your pediatrician,” advises Casares. She says a doctor might help pinpoint other factors, such as stress or sensory-seeking behavior, that might be prolonging the habit. Siddiqui also mentions difficulty sleeping as another possibly contributing factor.

Shira Newman, an Ardsley, New York mom of two elementary-school-age children, says both of her sons started sucking their thumbs at 10 weeks old. “During infancy, they both sucked their thumbs very often, typically when tired and falling asleep, as well as while sleeping,” she says. Her older son eventually outgrew the habit, but her younger son still sucks his thumb when tired or needing comfort — but not at school or in public. “As a former thumb sucker myself, I don’t see a problem with this self-soothing habit. I know my kids will outgrow it in their own time.”

“As a former thumb sucker myself, I don’t see a problem with this self-soothing habit. I know my kids will outgrow it in their own time.”

— SHIRA NEWMAN, MOM OF TWO

“Every baby follows their own trajectory when it comes to development and behavior, especially when it comes to self-soothing,” explains Casares, who notes that thumb sucking is not a developmental milestone and should never be forced. “All children are different and find unique ways to soothe themselves. There’s nothing to worry about if your child is not a thumb sucker, though.” 

She also notes that some experts suggest offering, but never forcing, a pacifier to baby thumb suckers (following this guidance from the American Academy of Pediatrics) for a variety of reasons — from studies that show it can help reduce the risk of Sudden Infant Death Syndrome (SIDS) to pacifiers being easier to clean and somewhat softer than fingers. 

The bottom line on thumb sucking?

Babies and thumb sucking simply go hand in hand. But, as with any self-soothing method, it can become a hard habit to eventually break.

“Similar to other habits like taking the bottle or pacifier, it is harder to stop the [thumb sucking] habit as the baby grows older and more dependent on the habit,” explains Siddiqui. “It is helpful if the baby uses multiple modalities to help to self-soothe to avoid one thing becoming a prolonged habit.” One way to do this, advises Siddiqui: “I always encourage parents to accentuate and encourage the positive behaviors and try to ignore [others] in order to diminish behaviors that need to be reduced.”

“I always encourage parents to accentuate and encourage the positive behaviors and try to ignore [others] in order to diminish behaviors that need to be reduced.”

— DR. SARA SIDDIQUI

And both she and Casares give a thumbs up to parents for discussing any and all issues about the growth and development of their little ones with their pediatrician or health care provider.