Not Sitting Up
The short answer
Most babies learn to sit independently between 6 and 9 months, with a wide range of normal. Before independent sitting, babies typically progress through sitting with support, then sitting with hands propped in front (tripod sitting), then sitting freely.
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By Age
What to expect by age
3-4 months
At this age, babies are working on head control and may sit briefly when well-supported, such as in a Bumbo seat or propped with pillows. They are not expected to sit on their own. Core strengthening through tummy time is laying the groundwork for sitting later.
4-6 months
Many babies begin sitting with support or in a "tripod" position, leaning forward on their hands for balance. Some babies may sit briefly unsupported by 6 months, but many are not yet ready, and that is perfectly normal. Lots of floor time and supported sitting practice helps.
6-7 months
This is when many babies achieve independent sitting, though they may still topple over sometimes. Some babies are more interested in rolling or scooting and come to sitting a bit later. As long as your baby is showing progress in their core strength and balance, they are likely on track.
7-9 months
Most babies are sitting well independently by this range and can reach for toys without falling over. Some babies, especially those who were premature, may take until 9 months. If your baby is not yet sitting with support by 8 months, a check-in with your doctor is a good idea.
9-12 months
If your baby is not sitting independently by 9-10 months, it is worth discussing with your doctor or health visitor. This does not necessarily mean something is wrong, as some babies are simply later developers, but an assessment can identify whether any support like physiotherapy would be helpful.
What Should You Do?
When to take action
- Your baby is under 6 months and not yet sitting independently, as this is earlier than most babies achieve this skill
- Your baby is sitting with support or in a tripod position and making gradual progress toward independent sitting
- Your baby can sit independently for short periods but still topples sometimes, showing they are building balance
- Your baby was premature and is reaching sitting milestones in line with their adjusted age rather than birth age
- Your baby prefers rolling or moving on their tummy and seems less interested in sitting still, but has the strength to sit when placed
- Your baby is 8-9 months and cannot sit even with minimal support
- Your baby seems to have difficulty holding their trunk upright and consistently slumps to one side
- Your baby was sitting independently but seems to have lost this ability
- Your baby is not sitting independently and also seems delayed in other motor milestones like rolling or reaching
- Your baby has a sudden loss of sitting ability or other motor skills they previously had
- Your baby cannot hold their head up or support their upper body at all by 6 months
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
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Related Physical Concerns
My Baby Seems to Use One Side More Than the Other
Babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes.
My Baby Only Army Crawls
Army crawling (also called commando crawling) is a completely valid and normal way for babies to move. Many babies army crawl for weeks or even months before transitioning to hands-and-knees crawling, and some skip hands-and-knees crawling entirely. What matters is that your baby is independently mobile and exploring their environment.
One Side of My Baby's Body Moves Differently
Babies should generally use both sides of their body equally. If one side consistently moves differently, is weaker, stiffer, or less coordinated, this warrants evaluation. Asymmetric movement can indicate hemiplegia (cerebral palsy affecting one side), brachial plexus injury, or other neurological conditions that benefit from early therapy.
My Baby Crawls Unevenly
While some variation in crawling patterns is normal, consistently favoring one side or dragging one limb while crawling warrants attention. Babies should use both arms and both legs relatively equally when crawling. Persistent asymmetry could indicate muscle tone differences, hip issues, or neurological concerns that benefit from early evaluation.
My Baby Still Has the Fencing Reflex (Persistent ATNR)
The asymmetric tonic neck reflex (ATNR, also called the fencing reflex) causes your baby to extend the arm on the side they are looking toward. It should integrate between 4-6 months. If the ATNR persists strongly beyond 6 months, it can interfere with bringing hands to midline, bilateral hand use, and rolling. Evaluation is recommended.
Signs of Ataxia in Babies and Toddlers
Ataxia refers to wobbly, uncoordinated movements that result from problems with the cerebellum (the brain's coordination center). Signs include an unsteady, wide-based gait, difficulty with precise hand movements, and intention tremor (shaking that worsens when reaching for something). If you notice these signs, evaluation by a pediatric neurologist is important.