Sitting up is a big deal — not because it in itself is fundamentally important (sitting does not equal survival), but because it offers parents a break and kids a better vantage point to play. But like crawling and even walking, this is a milestone that parents look out for, essential or not. So when do babies start sitting up? The short answer is that neurotypical babies born after a full 9-months will sit up on their own anytime between 4-months and 8-months-old. The longer and more accurate answer is that when a baby sits up is less important than how they look during the process of figuring it out. After all, a baby born prematurely might sit up a little later than that, as will a baby who isn’t given much practice sitting up. In other words, the act itself will look different based on the circumstances.
You wouldn’t know this if you were to read books outlining milestones that give you a distinct time period for when baby should, nay must, be sitting up (usually, they tell parents to panic by 9-months). However, the expectations for when babies will sit that are published in parenting books of pediatricians pamphlets are based largely on lab-based data collected from western, white, developed and educated cultures. If you take a cross-cultural look at the issue you’ll see that this is a limited viewpoint that can cause unnecessary worry about time periods when it comes to sitting up. There is a huge range of cultural norms for when a baby can sit independently and still turn out fine.
In a 2015 study, researchers from the City University of New York made in-home observations in six cultural groups around the world in order to understand sitting abilities in 5-months old babies. What they found was that sitting ability was tied to environmental and cultural factors that affected the opportunities babies had to practice sitting.
“Proficiency varied considerably within and between cultural groups,” the study authors note. They found that 64 percent of the babies could only sit with support at 5-months, and 36 percent sat independently. But the amount of time they could sit varied widely too. “Some infants sat unsupported for 20-plus minutes, in some cases so securely that mothers moved beyond arms’ reach of their infants even while infants sat on raised surfaces,” researchers noted.
Why did some babies sit independently sooner than others? Researchers noted that many babies, particularly babies in the United States, where often confined in infant furniture or carried by parents and had less opportunity to develop their core strength and practice sitting up. Babies in other cultures, on the other hand, were often placed in adult furniture with parents out of arm’s reach. That meant that developing balance and core strength was key.
So the timing of when a baby sits up by themselves will likely differ from home to home. It will also depend on how much opportunity a baby has to develop the core strength and neurological awareness of body position which will allow themselves to balance.
What’s more important for parents is to understand when there might be neurological or physiological barriers present that are preventing a baby from sitting. Parents will want to talk to their pediatrician if their baby is struggling to sit because their body appears to be overly rigid and flexes predominantly to one side. The same goes for babies that appear to be overly limp and jerky, making it difficult for them to control their body position. These qualities will become more important to bring up to a pediatrician the older a child gets. A baby who is not sitting by 12-months-old, despite having the opportunity to practice, will likely need some kind of intervention.
But for most parents, a baby will develop the ability to sit when they are good and ready. This means that parents with babies between the ages of 4-months and 8-months old will want to practice patience and give their baby plenty of time to figure it out.