ParentAI
‹ All guides

Under 1 year

Is My Baby Behind? Making Sense of Development in the First Year

Somewhere in the first year, most parents find themselves watching another baby roll, sit or babble and quietly counting the weeks. That worry is a sign you are paying attention, which is exactly what your baby needs. The first year holds an enormous range of normal, and knowing what that range looks like, what supports development, and which signs deserve a doctor's look turns vague anxiety into something you can act on.

Why this happens at this age

Babies change more in their first year than in any other, and they do it on their own schedule. The World Health Organization followed healthy babies on several continents and found that sitting without support appeared anywhere from around 4 to 9 months, hands-and-knees crawling from around 5 to 13 months, and walking alone from around 8 to 18 months. A milestone is a window, not a deadline.

The checklists doctors use are built with this in mind. The 2022 revision of the CDC's "Learn the Signs. Act Early." checklists lists each skill at the age by which at least three quarters of babies are doing it, so a skill missing at that age is a prompt for a conversation, not a verdict.

If your baby was born early, use their corrected age: count from the due date rather than the birth date, and keep doing so until about their second birthday. A baby born eight weeks early who is six months old by the calendar is developmentally a four-month-old.

Development also moves unevenly across domains. A baby who is throwing everything into learning to crawl may go quiet on babbling for a few weeks, then catch up in a burst. Some babies skip crawling altogether and bottom-shuffle or go straight to pulling up. Temperament matters too: a cautious baby may watch for weeks before trying what a bolder baby attempts at once. What matters is that your baby keeps gaining skills across all areas over time, and that nothing already learned goes away.

What helps

Give your baby unhurried floor time every day, including tummy time. Strength for rolling, sitting and crawling is built on the floor, not in a bouncer or car seat. From the first weeks, put your baby on their tummy on a firm mat for a minute or two, several times a day, while they are awake and you are watching, and lengthen it as they tolerate more. Lie down facing them, or place a mirror or a bright toy just out of reach.

Narrate ordinary care. Babies learn language from words directed at them by a person they know, not from talk in the background. Nappy changes, feeds and bath time are dozens of small language lessons a day if you talk through them: "Socks off. One foot, two feet. Now the warm water. Splash!" Singing works just as well.

Answer every sound and expression. Development researchers call this "serve and return": your baby offers a coo, a grunt or a look, and you return it. When your baby says "ba", say "ba" back, then pause and wait, even for ten seconds, so they learn that a conversation has turns. When they look at the cat, follow their gaze and name it. These small exchanges build the wiring for talking, attention and connection.

Read and point together. From a few months old, a sturdy board book on your lap is worth a few minutes a day. Point at the picture and name it, then watch where your baby looks. By nine or ten months, many babies will follow your pointing finger and, a little later, point themselves, an early step in shared attention.

Keep screens out of the picture for now. Paediatric guidance is to avoid screen media, apart from video chat with family, before about 18 months, because babies cannot yet learn from a screen the way they learn from a face. If a video usually fills the gap while you cook, try a basket of safe kitchen items on the floor near you instead.

Keep a simple note of what your baby does and when. A dated line in a phone note is enough: "rolled front to back", "laughed at peekaboo", "turned when I said their name". Over a few weeks it shows what worry cannot: whether skills are steadily arriving. It also gives your doctor something concrete to work from.

What to avoid

Comparing your baby to other babies or to online charts. A friend's baby walking at nine months tells you nothing about yours, and charts on social media often quote averages rather than the full range, so half of all healthy babies look "late" on them. Compare your baby with themselves a month ago.

Drilling skills. Holding a baby in a standing position for long spells, propping them to sit before they can hold the position, or running through "exercises" several times a day does not speed anything up. Baby walkers do not bring walking forward and carry a real injury risk. Your baby's own play, with you nearby, is the practice.

Talking yourself out of your instinct. Parents are often the first to notice that something is different, sometimes months before anyone else. Reassurance from relatives is kind, but it is not an assessment. A worry that keeps returning deserves a proper look.

Waiting months to "see". In the first year, three months is a large fraction of your baby's life. If a specific skill from the list below is missing, ask now. If the check shows all is well, you have lost nothing; if support is needed, you have gained a head start.

When to seek help

Talk to your paediatrician, family doctor or health visitor and ask for a developmental check if you notice any of the following. They are drawn from CDC and American Academy of Pediatrics milestone guidance and are prompts for an assessment, not a diagnosis.

By around 2 to 3 months: your baby does not react to loud sounds; does not look at your face or follow you briefly with their eyes; does not smile at people; cannot lift their head at all during tummy time; or seems unusually stiff or unusually floppy.

By around 4 months: does not hold their head steady when held upright; makes no sounds other than crying, or does not coo back when you talk; does not bring their hands to their mouth; or does not turn towards your voice.

By around 6 months: does not reach for or grasp objects; does not roll in either direction; does not laugh or squeal; shows no interest in people; or uses one side of the body much more than the other.

By around 9 months: does not babble with repeated sounds such as "bababa"; does not look when you call their name; does not sit, even with support; does not pass objects from one hand to the other; or does not smile or laugh at peekaboo.

By around 12 months: does not pull up to stand; does not use gestures such as waving or lifting their arms to be picked up; does not look for something they see you hide; does not respond to their name; or shows a strong preference for one hand.

At any age: your baby loses a skill they previously had, whether sounds, movements or social responses. This always warrants a prompt check.

Screening is a normal part of infant care: the American Academy of Pediatrics recommends formal developmental screening at 9 months and again in the second year, on top of the questions asked at every visit, so raising a concern simply brings that conversation forward. When a delay is found, support can begin before any diagnosis exists, and the earlier it starts, the more your baby's growing brain can make of it.

Sources

This guide is general information, not medical or psychological advice. If you are worried about your child, talk to a doctor or another qualified professional.