Developmental milestones: sitting

When do babies start sitting up?

Your baby will gradually learn to sit from three months and will sit independently by nine months old (Sharma et al 2022). The muscles they need to use develop gradually from birth, and they finally become strong enough to sit on their own when they're about six months to seven months. They may not be quite balanced though and will still fall over if they lean to one side to reach for something.

By the time your baby is about eight months old, they should be showing signs they can sit and balance well without any support or you helping them (NHS Inform 2023, Sharma et al 2022). Nearly all babies can get into a stable sitting position on their own by the time they are nine months old (Sharma et al 2022).

How will my baby learn to sit up?

Sitting independently doesn't begin until your baby has stronger back muscles and better head control.

Three months to four months

Your baby's neck and head muscles are strengthening rapidly. From this time onwards, they'll learn to raise and hold their head up while they're lying on their tummy (Sharma et al 2022).

Next they'll figure out how to prop themselves up on their arms and hold their chest off the floor, like a mini-push-up (Sharma et al 2022).

If you pull your baby to a sitting position at this stage, their upper back will be straighter and stronger than when they were newborn. They can also hold their head upright and steady while you support them (Sharma et al 2022).

Five months to six months

Your baby will be able to sit well with support, holding their back straight and their head up (Sharma et al 2022). They'll have enough strength and coordination to move their head from side to side to look around (Sharma et al 2022).

Your baby may even be able to sit for a moment without your help by leaning on their hands (CDC 2023a). Make sure you stay nearby to provide support, or surround them with pillows in case they fall.

Seven months to eight months

Your baby may sit unsupported with their back straight and their legs out to the sides to support them and give them stability (CDC 2023b). This will free their hands for exploring, and they'll learn how to turn when sitting to reach for a toy (Sharma et al 2022).

At this point, they may even be able to get into a sitting position from lying on their tummy by pushing up on their arms (CDC 2023b, Sharma et al 2022). By the time they're nine months old, they're likely to be sitting well without support (Sharma et al 2022).

Once my baby can sit, when will they start crawling?

Once your baby works out how to lunge forward from a sitting position and balance on their hands and knees, they will be almost ready to crawl.

Crawling is a skill most babies get the hang of by the time they're a year old. They may be able to move forwards or backwards on all fours as soon as they're six months or seven months. But most babies don't learn to crawl for a few more months after that (Sharma et al 2022).

Once your baby can crawl, they'll be on the move all the time, bent on exploring all the fascinating new territory now open to them. Try to make your home as safe as possible before your little explorer gets going (NHS 2023a).

How can I encourage my baby to sit up?

You can help your baby learn to sit by encouraging them to play lying on their tummy as much as possible (APCP 2016). Try to get them to look up, by using noisy, bright and colourful toys, or by pulling funny faces and making sounds (AAP 2023).

This helps to strengthen their neck, shoulder, and back muscles and in turn gives them the head control they need for sitting up (APCP 2016).

Here are some other tips to help your baby learn to sit up:

• When they're first learning, sit on the floor with them, supporting them around their body.
• Your baby will need to prop on their hands as they learn to sit. You can help them learn this by putting firm and sturdy toys in front of them to lean on.
• Give them as little support as they need, so that their tummy and back muscles get stronger.
• As they get better at sitting, you can give them less support.
• Some parents use a play ring to give their baby extra support. Your baby sits inside and you place toys in or on the ring so that they can play.
  (Somerset NHSFT 2023)

As always, and especially when they're just learning to sit, be sure to stay close to your baby in case they fall.

My baby is nine months and still can't sit up. Should I be worried?

If your baby isn't showing signs of sitting on their own by the time they're eight months old, talk to your doctor or health visitor about it (NHS Scotland 2024). All babies develop skills differently, some more quickly than others. But if you think your child isn't developing as they should, or you're worried about anything, trust your instincts.

If your baby was born early (before 37 weeks of pregnancy) or with a condition linked with developmental delays, such as Down's syndrome, keep in mind that they may reach this and other milestones a little later than other babies (AAP 2020, NHS 2023b).

Find out when your baby may hit these physical milestones:

• Crawling
• Standing
• Walking