When do babies sit up by themselves, and what can we do to help them?

© 2020 Gwen Dewar, all rights reserved

Most babies learn to sit up by themselves sometime between 4
and 8 months. But the process is gradual, and some babies make faster progress
than others.  We can give motor development a
boost by helping babies build key muscles.

When do babies sit up by themselves? There isn’t any one, universal answer.

Around the world, approximately half of all babies have learned to sit independently by the age of 6 months. But some babies reach this milestone much earlier — as early as 4 months. And other babies take much longer — 8 months or more. 

Why does the timing vary so much? 

To some degree, the timing depends on genetics.

For example, some babies might be born with a genetic tendency to be more physically active. As a consequence, they get more exercise, and this helps them learn new motor skills at a raster pace.

But it’s also evident that the environment matters. Quite a lot!

For instance,  in a study of infants living in the United Kingdom, researchers found that approximately half the variation in the timing of sitting was caused by differences in the environment. Some children were growing up in environments that favored earlier development (Smith et al 2017). 

So what’s considered normal? When should a parent be
concerned about the possibility of a developmental delay?

Experts offer this rule of thumb: If your baby hasn’t begun
to sit up by the age of 9 months, talk to your doctor. Your doctor can screen
your baby for problems. If something’s not right, early intervention will help
your baby get back on track.

But there’s nothing magical about 9 months. If you see
something that bothers you — if something seems off — you shouldn’t wait
until 9 months. Especially if your baby is approaching the 9 month mark and seems
to have trouble sitting with support. Trust your instincts and consult your

And if your baby is older than 9 months? That doesn’t mean
your baby has a developmental problem. For many infants, taking longer is just
a reflection of their personal quirks and experiences. As we’ll see below,
babies learn to sit up earlier when they get more opportunities to practice. And we can do a great deal to help them.

So why the focus on 9 months? And where do these other
numbers come from? How do we know what’s typical or normal?

Ultimately, the numbers come from scientific surveys.
Researchers recruit families with young infants, and track development over
time. Parents report when their babies achieve certain motor milestones.

For example, in one study, the World Health Organization
tracked more than 1,100 babies in six different countries.

Every month, researchers asked parents about their infants’
motor development. And after all the data were collected, researchers found
that approximately 95% of the babies had learned to sit up (unassisted)
sometime between the ages of 4.3 months and 8 months. About half of all babies
in the study had learned to sit up independently by the age of 5.9 months
(Matorell et al 2006).

So it’s numbers like these that experts use to make
generalizations about what to expect. They aren’t numbers that tell us what
“should” happen. They are numbers that tell us what actually happened…among babies participating in a specific study.

And here’s what’s interesting: We can get very different
numbers depending on where we look.

The “normal” or
“typical” age range for sitting up isn’t the same in every county. It
varies. Sometimes pretty dramatically. And the variation maps onto what we know
about local parenting practices.

To see what I mean, consider the West African country of

xWhen do babies sit Ghana mother and infant by Anton Ivanov shutterstock 200x300 min.jpg.pagespeed.ic.0WauxrtlHa - When do babies sit up by themselves, and what can we do to help them?Image of Ghanaian mother and baby by Anton Ivanov

In Ghana, parents don’t wait passively for their babies to
experiment with new motor skills!

Like parents in many other African and
Caribbean countries, they actively train their babies. For example, caregivers
use their hands and supportive objects to help young infants practice sitting
in an upright position (Adolf et al 2010; Karasik et al 2015). And the outcome?

In Ghana, the average (mean) age for learning to sit up
independently is approximately 5.1 months. Around 95% of babies in Ghana reach
the milestone between the ages of 3.5 and 6.7 months.

By contrast, let’s take a look at a country in Northern
Europe — Norway. Parents in Norway usually take a more “wait and see”
approach to physical development. They don’t coach their children to sit
upright, and the outcomes are quite different:

In the World Health Organization study, the average
Norwegian baby didn’t begin sitting up independently until about 7 months.  And roughly one-third of babies didn’t reach
the milestone until they were at least 8 months old (Matorell et al 2006).

So if we used data from Ghana to evaluate Norwegian babies,
we might think that Norway is plagued by developmental problems. One third of
Norwegian babies are so slow they fall outside what we might call the
“normal range of variation” in Ghana.

But are these babies suffering from a medical condition? Are
they challenged by a disease, or a physical disability, or a cognitive

In most cases, no. They’re just taking longer — most likely
because they haven’t had the same opportunities to practice and develop their
motor skills.

How, then, can you boost infant motor development? How can you help your baby learn to sit up?

The key is to provide your baby with the right sort of physical activities — activities that recognize your baby’s current limitations, but also encourage your baby to push those limits.

Where to begin? It’s helpful to understand the basic challenge that babies face.

To sit upright,
babies need to something called “trunk control.” They need to build
strength in core muscles throughout the neck, torso, and spinal column. And they develop this strength one segment at a time, in a specific, “top-down” sequence (Pin et al 2019):

  • First, they build strength in their neck muscles.
  • Next, they begin developing stronger muscles in the upper
    (thoracic) region of the torso.
  • Then — once they’ve developed a strong thoracic region —
    they start building up the muscles of the lower trunk (the lumbar region).

Many parents seem to have
an intuition about this sequence. You can see it when they hold their babies

When a baby is very young and weak, parents typically hold onto the
baby at the shoulders. But as the baby gets stronger, parents hold onto the
upper or mid-back. And when a baby is nearly ready to sit up unsupported,
parents place their hands around the lower back or hips.

So if you pay attention to your baby’s wobbles, you’ll
quickly get a feeling for where your baby is in the sequence. You’ll have a sense of which muscles are already strong, and which muscles need conditioning.

Here are some
things you can do at each stage of the process.

Six tips for teaching babies to sit upright

1. Help your baby develop strong neck muscles with  “tummy time.”

xTummy time dad baby cropped FlamingoImages istock 300x min.jpg.pagespeed.ic.tuB5 HaI6j - When do babies sit up by themselves, and what can we do to help them?

Safety experts urge us to place young infants on their backs
for sleeping. This tactic reduces the risk of SIDS.  But when babies are awake and alert, they
benefit from supervised sessions on their stomachs — especially if their
caregivers make it a fun, social experience.

Such “tummy time” can speed up the development of
certain locomotor skills, like crawling. And because tummy time gives babies
the opportunity to develop greater muscle control and neck strength, it may
help babies prepare for sitting up by themselves (Kuo et al 2008; Hewitt et al

Does your baby dislike being placed on the floor? As an
alternative, try lying down and place your baby on your chest.

2. Help your baby strengthen core muscles of the torso with more
tummy time, and with opportunities to roll around.

xBaby rolling by Gwill shutterstock 300x.jpg.pagespeed.ic.jql 8eweJa - When do babies sit up by themselves, and what can we do to help them?

Rolling over is another one of those motor milestones that
can vary a lot in timing: Some babies can do it before 3 months. Others may
take 6 months.

But whenever it happens, it’s a big step in the direction of
being ready to sit up. That’s because rolling around builds the strong, core muscles
that babies need to stabilize themselves in an upright position.

3. Give your baby a
taste of what it feels like to sit up. Become a living chair.

xLiving chair mom baby RobertoDavid istock 300x min.jpg.pagespeed.ic.Io1QPN8VMW - When do babies sit up by themselves, and what can we do to help them?

This is a common technique in cultures where parents take a
proactive approach to motor development. Newborns aren’t just cradled and
carried. They are also placed upright, in a sitting position, on their
caregivers’ laps. The adult holds the baby in place, and becomes a kind of
living chair — one that the baby can lean against.

4. Is your baby strong enough to hold up his or her own head? Then your baby is ready to try sessions of
supported sitting on the floor.

xbaby sitting propped up Sasiistock istock 300x min.jpg.pagespeed.ic.OZAOjAMGOx - When do babies sit up by themselves, and what can we do to help them?

Follow another cue of proactive parents: Seat your baby on
the ground, with furniture, cushions, or other props to keep your baby from
toppling over.

When you try this, your baby should already have strong neck
muscles. What’s needed now is more strength in the shoulders, waist, and hips.

Your baby is learning to cope with gravity, learning how to
counteract every little tug and tilt. Staying upright requires instantaneous
adjustments in the stiffness of many different muscles. It’s quite a trick!

So it’s no wonder if your baby can only stay upright for a
few seconds at a time.  But those moments
— however brief — are long enough to make a difference.

5. Watch for “tripod sitting” — an early stage of
sitting up where babies use their arms to prop themselves up.

xtripod stance infant stacey newman istock 300x min.jpg.pagespeed.ic.rw  GhcV0S - When do babies sit up by themselves, and what can we do to help them?

Now “tummy time” is better termed “floor
time,” because your baby is capable of sitting up by him or herself — at
least for brief periods of time. At first, your baby’s stance will probably
look rather bent or hunched forward , and your baby may require both hands on
the ground to stay upright.

But your baby will begin to experiment with lifting one
hand, and slowly learn how to adjust his or her balance. You can encourage this
process by playing with your baby face-to-face, and offering your baby
interesting objects to hold. And this brings us to my last suggestion…

6. Understand how your baby’s world is changing. Be
ready to provide your baby with new learning opportunities!

xMom baby sitting eye contact by Monkey Business Images shutterstock 300x min.jpg.pagespeed.ic.vHscq1tOIo - When do babies sit up by themselves, and what can we do to help them?

Sitting up, unsupported, is more than a motor milestone.
It’s also a trigger for new environmental experiences — experiences that can
give your child a cognitive boost.

Once babies can sit up — without having to use their hands
to keep their balance — it’s easier for them to reach for objects. It’s also
easier for them to manipulate and visually examine objects, and that
helps them learn about objects (Woods and Wilcox 2013).

It’s also likely that sitting up helps babies learn
language. It’s easier for them to make eye contact, and this can stimulate more face-to-face conversation with their caregivers. They get exposed to more words, and begin learning new vocabulary at a
faster pace (Libertus and Violi 2016).

So be ready to provide your baby with the stimulating social and cognitive rewards of sitting. Don’t leave your baby alone in chair with nothing to do. Encourage your baby to investigate, observe, communicate, and learn.

More reading about your baby’s development

Do you have other questions about your baby’s development? Check out these Parenting Science articles:


Adolph KE, Karasik LB, Tamis-LeMonda CS. 2010. Motor skills. In:
Bornstein MH, editor. Handbook of cross-cultural development science. Vol. 1.
Domains of development across cultures, pp. 61–88 Hillsdale, NJ: Erlbaum.

Gonzalez SL, Alvarez V, Nelson EL. 2019. Do Gross and Fine
Motor Skills Differentially Contribute to Language Outcomes? A Systematic
Review. Front Psychol. 10:2670.

Hewitt L, Kerr E, Stanley RM, Okely AD. 2020. Tummy Time and
Infant Health Outcomes: A Systematic Review. 
Pediatrics. 145(6):e20192168.

Karasik  LB,
Tamis-LeMonda  CS, Adolph  KE, and Bornstein  MH. 2015. Places and postures: A
cross-cultural comparison of sitting in 5-month-olds.  J Cross Cult Psychol.  46(8):1023-1038.

Kuo YL, Liao HF, Chen PC, Hsieh WS, Hwang AW. 2008. The
influence of wakeful prone positioning on motor development during the early
life. J Dev Behav Pediatr. 29(5):367-76.

Libertus K, and Violi DA. 2016. Sit to Talk: Relation
between Motor Skills and Language Development in Infancy. Front Psychol. 7:475.

Martorell R, Onis M, Martines J, Black M, Onyango A, Dewey
KG. 2006. WHO motor development study: Windows of achievement for six gross
motor development milestones. Acta Paediatrica. 95(S450):86–95.

Oudgenoeg-Paz O, Leseman PP, Volman MC. 2015. Exploration as
a mediator of the relation between the attainment of motor milestones and the
development of spatial cognition and spatial language. Dev Psychol.  51(9):1241-53.

Oudgenoeg-Paz O, Volman MC, Leseman PP. 2012. Attainment of
sitting and walking predicts development of productive vocabulary between ages
16 and 28 months.  Infant Behav Dev.

Relationship between segmental trunk control and gross motor
development in typically developing infants aged from 4 to 12 months: a pilot

Pin TW, Butler PB, Cheung HM, Shum SL. 2019. Relationship
between segmental trunk control and gross motor development in typically
developing infants aged from 4 to 12 months: a pilot study. BMC Pediatr. 19(1):425.

Smith L, van Jaarsveld CHM, Llewellyn CH, Fildes A, López
Sánchez GF, Wardle J, Fisher A. 2017. Genetic and Environmental Influences on
Developmental Milestones and Movement: Results From the Gemini Cohort Study. Res
Q Exerc Sport. 88(4):401-407

Valla L, Slinning K, Kalleson R, Wentzel-Larsen T, Riiser K.
2020. Motor skills and later communication development in early childhood:
Results from a population-based study. Child Care Health Dev. 46(4):407-413.

Valla L, Wentzel-Larsen T, Hofoss D, Slinning K. 2015.
Prevalence of suspected developmental delays in early infancy: results from a
regional population-based longitudinal study. BMC Pediatr. 15:215.

Woods RJ and Wilcox T. 2013. Posture support improves object
individuation in infants. Developmental Psychology 49(8): 1413–1424.

Saavedra SL, van Donkelaar P, Woollacott MH. 2012. Learning
about gravity: segmental assessment of upright control as infants develop
independent sitting. J Neurophysiol. 108(8):2215-29.

Valla L, Wentzel-Larsen T, Hofoss D, Slinning K. 2015.
Prevalence of suspected developmental delays in early infancy: results from a
regional population-based longitudinal study. BMC Pediatr. 15:215.

Title image of three babies sitting by Rawpixel / istock

Image of Ghanaian mother and infant by Anton Ivanov / shutterstock

Image of father with baby on floor by FlamingoImages / istock

Image of baby rolling over by Gwill / Shutterstock

Image of mother being a living chair for infant by RobertoDavid / istock

Image of baby sitting on floor, propped up on pillows by Sasiistock / istock

image of baby sitting in a tripod stance by Tracey Newman / istock

Image of mother with baby in a park by MonkeyBusinessImages / Shutterstock

Content last modified 12/2020

Copyright © 2006-2020 by Gwen Dewar, Ph.D.; all rights reserved.

For educational purposes only. If you suspect you have a medical problem, please see a physician.


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