Summary
Every baby develops at their own pace, but there are certain developmental red flags that parents should not ignore. Knowing baby milestones by age can help parents recognise when a child may need a little extra support. Delays in movement, communication, social interaction, hearing, vision or problem-solving can sometimes indicate baby developmental delays. A single missed milestone does not necessarily mean something is wrong, but a pattern of delays, a significant difference from expected development, or losing a skill that a baby previously had deserves attention. Early assessment can help identify the reason for the delay and, when needed, connect families with appropriate support.
Baby development: when should parents start paying attention?
Watching your baby learn new skills is one of the most fascinating parts of early parenthood. First comes that tiny social smile, then the excited kicking, babbling, reaching, rolling, sitting and eventually those first attempts at communication and walking.
But alongside the excitement often comes another question: “Is my baby developing normally?”
Parents today have access to endless information about baby milestones by age. This can be reassuring, but it can also create anxiety. One baby is sitting at five months, another at seven. One is babbling constantly while another is quieter. A friend’s baby may be crawling at eight months while yours appears perfectly happy lying on the floor and exploring with their hands.
So, when should you actually worry?
The important thing to understand is that developmental milestones are guidelines, not examination results. Babies do not all follow an identical timetable. Most reach developmental skills within a broad expected range, and some variation is completely normal.
What matters more is the overall pattern of development.
A baby who is progressing gradually, interacting with people, learning new skills and showing curiosity may simply have their own timetable. A baby who is consistently missing several age-appropriate skills, seems unusually difficult to engage with, is not progressing, or loses a previously acquired skill should be assessed.
That distinction is at the heart of understanding developmental red flags.
What are developmental milestones?
Developmental milestones are skills that most children can accomplish by a particular age. They cover several areas of development rather than simply physical abilities.
These include:
- Gross motor skills: movements involving the larger muscles, such as holding the head up, rolling, sitting, crawling and walking.
- Fine motor skills: using the hands and fingers to grasp, transfer and manipulate objects.
- Communication: making sounds, babbling, understanding language and eventually using words.
- Social and emotional development: smiling, making eye contact, responding to familiar people and engaging in interaction.
- Cognitive development: learning, exploring, remembering and solving simple problems.
This is why development should not be judged by asking only, “Is my baby sitting?” A baby may be physically progressing well but have concerns with communication or social interaction, for example.
The CDC’s milestone resources similarly organise development across areas such as social-emotional, language, cognitive and movement skills.
Baby milestones by age: what should you generally expect?
Rather than treating milestones as deadlines, think of them as useful checkpoints.
Around 2 months
By around two months, many babies are beginning to look at faces, smile in response to interaction, react to loud sounds and make sounds other than crying. They may also briefly hold their head up when on their tummy.
If your baby rarely looks at faces, does not appear to respond to sound, or seems unusually floppy or difficult to engage, mention this to your paediatrician.
Around 4 months
At approximately four months, babies commonly become much more socially interactive. They may smile spontaneously to get your attention, chuckle, make cooing sounds, turn towards your voice and hold their head more steadily.
They also begin reaching for objects and may bring their hands to their mouth.
Around 6 months
Six months often brings a noticeable change in interaction. Babies may recognise familiar people, laugh, make a wider variety of sounds, reach for toys, explore objects with their mouth and begin rolling in both directions.
They may also begin sitting with support and show greater interest in their surroundings.
A baby who is not responding to sounds, showing little social interaction or demonstrating very poor head control should be discussed with a healthcare professional.
Around 9 months
By nine months, many babies are sitting without support, transferring objects between hands, reaching for things they want and making a variety of sounds.
Social communication becomes increasingly important. Babies often enjoy games such as peekaboo, respond to their name and use facial expressions, sounds and gestures to communicate.
The back-and-forth nature of interaction is particularly valuable to observe.
Around 12 months
By one year, many babies are pulling themselves up, moving around while holding furniture, using gestures such as waving, making sounds that resemble words and understanding simple requests.
They may point, imitate actions and enjoy social games.
Not every 12-month-old will be walking or saying several recognisable words. Those individual differences can be completely normal. What is more important is whether the baby is continuing to acquire skills and communicate in other ways.
The developmental red flags parents should know
So, what are the signs that deserve closer attention?
Rather than memorising a huge list, look for patterns.
1. Your baby is not gaining new skills
Development is a process of progression. Babies should gradually become better at controlling their bodies, interacting with people, communicating and exploring.
If several months seem to pass without noticeable progress, speak to your child’s doctor.
A delay in one area does not automatically indicate a serious problem. Some children have an isolated delay, while others have delays across several areas. The reason can range from hearing difficulties or differences in temperament to prematurity, medical conditions or developmental disorders.
The important point is that you do not have to diagnose the reason yourself.
2. Your baby seems unusually floppy or unusually stiff
Muscle tone varies between babies, but significant concerns include a baby who feels persistently very floppy, has difficulty holding their head up, or appears unusually stiff.
You may also notice unusual postures, persistent asymmetry or one side of the body being used much more than the other.
Movement-related developmental delays can sometimes be an early sign of an underlying motor or neurological issue, although there can be many different explanations.
This is a situation where professional assessment is much more useful than comparing your baby with another child.
3. Your baby does not respond to sounds or voices
Hearing plays an enormous role in communication and language development.
If a baby does not seem to startle or react to loud sounds, turn towards voices, respond to familiar sounds or show awareness when someone speaks to them, hearing should be considered.
Sometimes what looks like a speech or communication delay is actually related to hearing.
If you have concerns about your baby’s hearing, do not wait for them to “grow out of it”.
4. There is very little social interaction
Babies are naturally interested in people, although individual personalities vary.
A baby who rarely looks at faces, does not seem interested in interaction, does not smile socially or rarely responds to attempts to engage them deserves closer observation.
Social communication is particularly important because it involves several skills working together: looking, listening, smiling, responding, making sounds and eventually using gestures.
The AAP notes that paediatricians look at behaviours such as eye contact, responding to names, pointing, waving and attempts to regain a parent’s attention when monitoring development.
Signs of autism in babies: what should parents look for?
The phrase “signs of autism in babies” can understandably cause enormous anxiety.
It is important to be careful here. Autism cannot be diagnosed simply because a baby does not meet one milestone. Babies develop differently, and many behaviours associated with autism can also occur temporarily or for other reasons.
However, differences in social communication and interaction can sometimes become noticeable during infancy and toddlerhood.
Parents may want to discuss concerns if their baby consistently:
- does not respond to their name or familiar voices;
- makes very little eye contact;
- shows limited interest in people;
- rarely uses gestures such as pointing, reaching or waving as they get older;
- has limited back-and-forth interaction;
- does not appear to share enjoyment with caregivers;
- shows unusual repetitive movements or behaviours;
- loses social or communication skills they previously had.
The NHS emphasises that autistic people are very different from one another and that not everyone will show the same signs. Autism may become apparent at different ages.
Most importantly, a developmental concern is not the same thing as an autism diagnosis.
If you notice several of these behaviours, the right next step is assessment, not panic or self-diagnosis.
The red flag that should never be ignored: regression
There is one developmental concern that deserves particular emphasis: loss of a skill that your baby has already acquired.
For example, if your baby was previously babbling, responding socially or using a particular movement and then stops doing so, tell your paediatrician.
Regression is different from simply being a little late with a milestone. A child who has not yet learned a skill may simply be developing at a different pace. A child who has learned a skill and then loses it needs evaluation.
CDC developmental guidance specifically advises parents to inform their healthcare professional if a child loses skills at any age.
Do not wait several months hoping that the skill will return on its own.
When to worry about baby milestones — and when not to
This is probably the question parents ask most often.
The answer is: look at the whole child, not one milestone.
For example, a baby who is not crawling at an age when another baby is crawling may not have a developmental problem. Some babies crawl later, shuffle, bottom-scoot or move directly towards standing and walking.
Similarly, a baby who is not yet saying words may still be communicating through eye contact, gestures, sounds and facial expressions.
However, concern becomes more important when:
- several milestones are missing;
- there is little progress over time;
- development appears significantly different from peers across more than one area;
- your baby is not responding to sound or interaction;
- there are concerns about muscle tone or movement;
- communication appears unusually limited;
- or your baby loses previously acquired skills.
And there is another important rule: if you are worried, you do not have to wait until the next routine appointment.
Developmental screening can be undertaken whenever a parent or healthcare professional has a concern. The AAP recommends routine developmental screening at 9, 18 and 30 months, with autism-specific screening at 18 and 24 months.
What should parents do if they notice a developmental red flag?
First, resist the temptation to search for a diagnosis online.
Instead, observe your baby carefully and write down what you are seeing.
You might note:
What can my baby do?
For example, “She smiles when I talk to her but rarely turns towards sounds.”
What concerns me?
For example, “He was babbling regularly but has stopped over the last month.”
When did I first notice it?
A timeline can be extremely useful to your healthcare professional.
You can also record a short video of a behaviour that concerns you. Babies do not always behave in the same way during a clinic appointment, so a video can sometimes provide useful information.
Take your concerns to your paediatrician or other appropriate child-health professional. They may assess your baby’s development, hearing, vision, physical health and behaviour and decide whether further assessment is appropriate.
Early assessment does not mean something is definitely wrong. It means that if support is needed, you have an opportunity to provide it sooner.
How parents can support healthy development at home
You do not need expensive developmental toys or elaborate activities.
Babies learn through everyday interaction.
Talk to your baby while feeding, bathing and changing them. Respond to their sounds. Copy their expressions. Sing songs. Read picture books. Give them safe opportunities to move and explore. Provide supervised tummy time when appropriate and allow plenty of opportunities for floor-based movement.
Most importantly, interact with your baby rather than simply entertaining them.
The back-and-forth exchange between a baby and caregiver is powerful. Your baby makes a sound; you respond. Your baby smiles; you smile back. They reach for a toy; you name it. These seemingly ordinary moments provide opportunities for communication, movement, attention and social learning. NHS guidance similarly encourages talking, singing, responding to babies’ sounds and sharing books as ways of supporting early communication.
Development is not a race
One of the biggest mistakes parents can make is turning developmental milestones into a competition.
Your baby does not need to be the first to sit, crawl, walk or talk.
A milestone chart is a tool for observation, not a scoreboard.
Instead of asking, “Is my baby ahead or behind?” ask:
Is my baby learning? Is my baby progressing? Is my baby interacting? Is my baby gaining new skills?
And if something doesn’t feel right, trust that instinct enough to ask.
Parents know their babies incredibly well. Healthcare professionals bring a different kind of expertise, and the two work best together.
The goal of watching developmental milestones is not to create anxiety. It is to recognise children who may benefit from additional assessment and support as early as possible.
So, learn the baby milestones by age, understand the common developmental red flags, know the possible signs of autism in babies, and understand when to worry about baby milestones. But above all, remember that development is a journey, not a race.
A question asked early is rarely a wasted question.
Frequently Asked Questions
1. Does missing one baby milestone mean my baby has a developmental delay?
Not necessarily. Babies develop at different rates, and missing one milestone does not automatically mean there is a developmental problem. What matters is the overall pattern, whether your baby is continuing to make progress and whether there are concerns in several areas of development.
2. When should I speak to my paediatrician about developmental delays?
Speak to your paediatrician whenever you have a genuine concern rather than waiting for a particular age. It is especially important to seek advice if your baby is missing several milestones, is not progressing, has unusual muscle tone or movement, does not respond appropriately to sounds or social interaction, or loses a skill they had previously acquired. Developmental screening can be performed when concerns arise.
3. What are the early signs of autism in babies?
Possible early signs can include limited eye contact or social interaction, reduced response to their name or voices, limited back-and-forth communication, fewer gestures and unusual repetitive behaviours. However, these signs do not by themselves diagnose autism. Every autistic child is different, and assessment by an appropriately qualified professional is needed.
4. Is developmental regression more concerning than a late milestone?
Yes. Losing a skill that a baby has previously acquired is particularly important to discuss with a healthcare professional. Regression is different from simply reaching a milestone later than another child and warrants timely assessment.
About the author
Sonali Shivlani is a Pregnancy and Parenting Consultant with more than 22 years of experience supporting expecting and new parents. She is the Director and Senior Trainer at CAPPA India and has worked with more than 45,000 families across her career. Sonali is also the author of three books — Prenatal Fitness 360, Parenting Mantras and SuperMoms Recipes — and regularly works with families on pregnancy, childbirth, breastfeeding, newborn care, nutrition and early parenting.
Through her work, Sonali focuses on making evidence-based pregnancy and parenting information practical, reassuring and relevant to real families. Her approach combines professional expertise with the perspective of a mother of two adult children, helping parents navigate the early years with confidence rather than fear.
