Week 40

Days 274 to 280 · 39 weeks 0 days to 39 weeks 6 days old · about 9 months This week your baby has been out in the world for about as long as they grew inside you. A typical baby now measures about 71 cm (28 in) and weighs about 8.6 kg (18.9 lb), but babies vary widely, and what matters is that your baby follows their own curve on the growth chart. Many are crawling or finding their own way to get around, pulling up on furniture and babbling in long, chatty strings. You may feel more settled in your days, even if nights are still patchy. This week opens Part Five, the last three months of the year. It covers the 9-month check and developmental screening, standing alone, why baby walkers are unsafe, comparing babies, and how much your baby learns by copying you.

Day 274 · 39 weeks 0 days old

Nine months in, nine months out

There is an old saying that a baby spends nine months on the inside and needs nine months on the outside. Today you reach that point. Your baby has now lived as long in your arms as they did in the womb.

Look at the difference. Nine months ago your baby could not hold up their head, focus on your face across a room or keep their hands open. Now they may sit, crawl, reach for exactly the toy they want and protest loudly when you leave. They know your voice, your smell and your routines, and they have opinions.

You have changed too. Whatever kind of birth you had and whatever the months since have held, you have learned a person from scratch. You can probably read your baby's tired cues, their hungry cry and their "I am bored" fuss faster than anyone else.

The last part of the year moves quickly. Over the next three months most babies start to stand, many take their first steps, some say a first word, and meals start to look more like family meals. It is a stage full of motion, and also full of small, funny conversations.

Try this: Find a photo from your baby's first week and put it next to one from today, then notice three things that have changed in each of you.

Day 275 · 39 weeks 1 day old

What happens at the 9-month check

Around now, many families have a checkup with their baby's doctor or nurse. In some places it happens at 9 months, in others at 8 to 10 months, and some areas fold it into the 12-month visit instead. Follow what your local schedule offers.

The visit usually starts with weight, length and head circumference, plotted on the growth chart. Your baby's doctor or nurse will look at the curve over time rather than a single number. They may listen to the heart and lungs, look at the eyes, ears, mouth and any new teeth, check the hips and feel the soft spot on the top of the head, which is slowly closing.

Expect questions about feeding, sleep and daily life. How are solids going? Is your baby getting iron-rich foods? Are you still giving vitamin D, if your baby is breastfed? Is the house babyproofed now that your baby is on the move? Some places also check for anemia around this age.

Vaccines at this visit differ a lot between countries. In some places none are due, while in others a measles-containing vaccine or a catch-up dose is given. Bring your baby's record so it can be updated.

It also helps to bring your own questions, written down. A short visit goes fast with a wriggly baby on your lap.

Try this: Start a note on your phone today and add any questions about your baby's sleep, eating or development as they come up, ready for the next visit.

Day 276 · 39 weeks 2 days old

Developmental screening is a conversation, not a test

At or around the 9-month check, you may be asked to fill in a questionnaire about what your baby can do. These screening tools usually cover a few areas: movement, hand skills, communication, problem solving and social behaviour. Questions might ask whether your baby passes a toy from one hand to the other, babbles sounds like "ba-ba", looks when you say their name or picks up small things with their fingers.

Screening is not a pass or fail exam, and your baby does not need to perform on the day. You are the expert on what they do at home, which is why many questionnaires are filled in by parents. Answer honestly rather than hopefully. If you are not sure, try the activity at home first.

A result outside the typical range does not mean something is wrong. It usually means "let us look more closely", which might be a repeat check in a few weeks, a hearing test or a referral for a fuller assessment. When a delay is found, early support makes a real difference, so a careful look is always worth it.

If your baby was born early, development is judged by corrected age until about 2 years. A baby born 6 weeks early is, developmentally, closer to 7 and a half months than 9.

Try this: If you have a screening questionnaire to fill in, do it on a calm day at home, trying any activities you are unsure of while your baby is rested and fed.

Day 277 · 39 weeks 3 days old

Standing alone, for a second or two

As you read a few weeks ago, many babies pull up on furniture and cruise along it. The next step is letting go. One day your baby may stand holding the sofa, get distracted by something in their hands, and stand there without support for a moment before sitting down with a thump.

Standing alone takes balance, strong legs and a lot of courage. Most babies manage it somewhere between about 9 and 14 months, and some go straight from cruising to walking with only brief solo standing in between. As with every milestone, the range is wide, and there is no advantage to arriving early.

You can help simply by giving your baby time on the floor, with sturdy furniture to pull up on and space to practise. Let them be barefoot indoors so their toes can grip. Resist the urge to hold them up by both hands for long periods; they learn balance best when they control their own body. Falls are part of learning to stand. Most are a gentle sit onto a well-padded diaper bottom. Learning to bend the knees and lower down, rather than toppling, comes with practice.

Try this: Sit on the floor a short distance from the sofa while your baby is standing at it, and hold out a favourite toy just within reach, then cheer whatever they do.

Day 278 · 39 weeks 4 days old

Why baby walkers are best left on the shelf

A baby walker is a seat on wheels that lets a baby who cannot yet walk scoot around the room. They can seem like fun, or a way to help a baby walk sooner. Child safety experts and pediatric bodies advise against them, and some countries have banned them outright.

The main problem is speed. In a walker, a baby can move about a metre (3 ft) in a second, far faster than a parent can react. The most serious injuries come from rolling down stairs, often in the walker, which can cause head injuries and broken bones. Walkers also lift babies high enough to reach hot drinks, stove handles, cords and cleaning products, and they can tip over at the edge of a rug or a step.

Walkers do not help babies walk earlier. Some studies suggest they may slightly delay walking, because babies in them do not use their muscles and balance in the same way, and they cannot see their own feet.

Better options are floor time, sturdy furniture to cruise along and, a little later, a stable push toy with a wide base. Stationary activity centres, which do not roll, are safer than walkers, but keep sessions short so your baby still spends plenty of time moving freely.

Try this: If a walker has been passed on to you, take the wheels off or pass it on to recycling, and clear a stretch of sofa or low table for your baby to cruise along instead.

Day 279 · 39 weeks 5 days old

Every baby has their own timetable

At a playgroup this week, you may notice one baby already walking, another crawling at speed and a third sitting happily in one spot, all born within a month of each other. It is natural to compare. It is also one of the quickest ways to rob yourself of enjoyment.

Babies put their energy into different skills at different times. One may be busy with movement while another is quietly building language or fine hand skills. A baby who walks at 9 months is not more intelligent than one who walks at 15 months, and early talkers are not necessarily early movers. Siblings in the same family often follow very different paths.

Comparisons can also creep in from social media, where you see other people's highlights. Nobody posts the day their baby refused every food or would not let go of their leg.

What matters is that your baby keeps making progress over time, and that you raise any real worries with your baby's doctor or nurse. If someone else's comment leaves you uneasy, ask yourself whether it is a genuine concern about your baby or just a difference in style.

For your partner: Next time you hear the other parent comparing your baby to someone else's, name one thing you have seen your baby learn this month, and share it out loud.

Day 280 · 39 weeks 6 days old

Your baby is watching and copying you

Around 9 months, imitation takes off. Your baby may copy a cough, a click of your tongue, a raspberry or the way you blow on hot food. They may hold a phone, or a block, to their ear because they have seen you do it. As you read recently, waving and clapping often come in around now, learned mostly by copying.

Imitation is one of the main ways babies learn. By watching and copying, they practise sounds that will become words, movements they will need for eating and dressing, and the give and take of social life. Researchers have shown that babies around this age can even copy an action they saw the day before, a sign that memory is growing.

This also means your baby is learning from how you act, not only from what you say. Gentle hands, calm voices, saying please and thank you, and the way you react when you are frustrated are all being absorbed.

You do not need special lessons. Copying games happen naturally in daily life: you make a sound, your baby makes it back, you copy their version, and the game goes on. Babies love being imitated as much as imitating. Try this: Sit face to face with your baby and copy whatever sound or face they make, then pause and see whether they copy you back.