Week 21

Days 141 to 147 · 20 weeks 0 days to 20 weeks 6 days old · about 5 months This week many babies measure about 64 cm (25.2 in) and weigh about 7.0 kg (15.5 lb). Babies vary widely, and what matters is your baby following their own curve on the growth chart. Drooling, chewing and gnawing are everywhere, and for some babies the first tooth is close. Your baby's eyes are now working much like an adult's, seeing colours and depth well. For you, the conversations at home may be turning to food, and to the small disagreements that come with sharing a baby. This week covers the signs of teething and what it does not cause, safe ways to soothe sore gums, brushing the first tooth, eye health, working as a team with your partner, and why solid food usually starts at around 6 months.

Figure 8. When baby teeth usually come in.

Day 141 · 20 weeks 0 days old

What teething looks like, and what it does not cause

As a tooth moves up through the gum, many babies chew on anything they can find, rub their gums or cheeks, pull at an ear on the same side, or seem fussier than usual. Some wake more at night or feed in a more restless way for a few days. Others show no sign at all.

Drooling and chewing on fists are often blamed on teething, but as you read in week 16, they are common from about 3 months, long before any teeth appear. They are part of how babies explore with their mouths.

Teething may bring a very slight rise in temperature, but it does not cause a true fever, diarrhea, vomiting, a runny nose, a rash on the body or a baby who is very unwell. Colds and tummy bugs often turn up at the same age. Putting every symptom down to teeth risks missing an illness that needs care.

Call your baby's doctor if your baby has a temperature of 38.0 °C (100.4 °F) or higher with other signs of illness, has diarrhea or vomiting, is feeding much less than usual, has fewer wet diapers, or seems unusually sleepy or unwell. Remember that fever needs urgent care in any baby under 3 months. Try this: If you suspect teething, look and feel along the gums for a swelling or a white edge before deciding that is the cause of any fussing.

Day 142 · 20 weeks 1 day old

Soothing sore gums safely

The simplest remedies are usually the best. Counter-pressure eases gum pain, so let your baby chew on a firm rubber teething ring or toy, rub their gums with a clean finger, or offer a clean, damp washcloth that has been chilled in the fridge. Cold teething rings should be chilled, not frozen, as very hard frozen items can hurt the gums. Wipe drool off the chin and neck often to prevent a rash.

If your baby is clearly uncomfortable and simple measures do not help, a pain reliever made for babies may be used. Acetaminophen (paracetamol) can be used at this age, and ibuprofen is usually given only from about 6 months and above a certain weight. Ask your pharmacist or follow the dose for your baby's weight on the package. Never give aspirin to a baby. Some popular remedies are not safe. Amber or other teething necklaces and bracelets carry a real risk of strangulation and choking, and there is no evidence they work. Numbing gels and liquids that contain benzocaine can cause a rare but serious blood disorder in babies and should not be used. Avoid homeopathic teething tablets and gels, some of which have been found to contain harmful ingredients, and skip hard teething biscuits, which can break off into choking-size pieces.

Try this: Put one clean teething ring and a damp washcloth in the fridge tonight so they are ready the next time your baby wants something to chew.

Day 143 · 20 weeks 2 days old

Brushing starts with the very first tooth

As soon as the first tooth breaks through, it can start to decay, so this is the moment to begin brushing. Baby teeth matter: they help with chewing and speech, and they hold space for the adult teeth that follow.

Use a small, soft toothbrush made for babies, or a clean finger brush. Most dental bodies now advise a fluoride toothpaste from the first tooth, but only a tiny smear, about the size of a grain of rice. This amount is safe even though your baby will swallow it, and the fluoride strengthens enamel. Some local guidelines differ slightly, so follow the advice where you live. Brush twice a day, including last thing before bed. Lay your baby on your lap with their head towards you, or sit them on your knee leaning back against you, and brush gently in small circles along the tooth and gum line. There is no need to rinse afterwards.

Before teeth appear, you can wipe your baby's gums with a clean, damp cloth once a day, if you like. It gets them used to the feeling. Try to avoid putting your baby to bed with a bottle of milk or juice, which bathes the teeth in sugar overnight.

Try this: Buy a soft baby toothbrush and a tube of fluoride toothpaste this week, and keep them by the change table so you are ready on the day the first tooth appears.

Day 144 · 20 weeks 3 days old

Your baby now sees the world in full colour

At birth, your baby saw mostly blurry shapes and strong contrasts. By around 5 months, vision has come a long way. Your baby sees the full range of colours, judges distance far better, and can follow a moving object smoothly with both eyes working together. They may stare at small details, recognize familiar faces across a room, and become fascinated by their reflection.

Depth perception is a big part of why reaching has become so accurate. It will also help later with crawling and climbing.

In the early weeks, eyes sometimes wander or cross briefly. By about 4 months, both eyes should line up and move together most of the time. Eye problems in babies are uncommon, but some need early treatment to protect vision.

Call your baby's doctor if your baby's eyes often cross, turn in or out, or do not move together after 4 months, if your baby does not seem to follow faces or toys, if one or both pupils look white, cloudy or yellowish, including in flash photos, if their eyes are always watery, or if they seem very bothered by light.

Try this: Hold your baby in front of a mirror and move slowly side to side, watching how their eyes track your face and their own.

Day 145 · 20 weeks 4 days old

When you and your partner do not agree

Babies bring a stream of decisions: how to handle nights, when to start solids, how much to spend, who gets a lie-in, whether to visit family. Even close couples find they disagree more in the first year, and many studies show that relationship satisfaction often dips for a while after a baby arrives. That dip is common, and for most couples it recovers.

Tiredness makes small things feel big. Try to keep important talks for a time when you are both fed, rested and not in the middle of settling a baby. Talk about what you each need rather than who is right, and remember you are on the same side: you both want a well, happy baby and a family that works. Disagreeing is also a chance to divide things fairly. Unspoken resentment often comes from unseen work, such as remembering appointments, buying diapers before they run out, or planning meals. Naming those tasks out loud and sharing them can ease a lot of tension.

Babies are not harmed by calm disagreement, but loud, frequent conflict is stressful for everyone. If you are going round in circles, a counsellor can help. If you ever feel unsafe, reach out for support straight away. Try this: Each write a list of the tasks you do in a typical week, including the invisible ones, then swap lists and pick one task to trade.

Day 146 · 20 weeks 5 days old

Why solid food waits until about 6 months

Around now, family and friends may start to ask when your baby will begin solid food. The widely agreed answer is: at around 6 months, and not before 4 months. If your baby was born early, use their corrected age.

For the first six months, breast milk or formula gives a healthy baby everything they need. Before about 4 months, a baby's gut, kidneys and swallowing are not ready for other foods, and starting very early has been linked to more illness and a higher risk of obesity later. Starting solids also does not help babies sleep through the night, despite what many people say. At around 6 months, things change. Your baby's iron stores from pregnancy start to run low, so they need iron-rich foods alongside milk. Most babies by then can sit with support, control their head and move food around in their mouth. Waiting much later than 6 months is not a good idea either, because babies need the iron and the chance to learn to chew.

Some families start a little before 6 months on their doctor's advice, but never before 17 weeks. You will read all about choosing and preparing first foods in week 24.

Try this: Look ahead in your calendar to the week your baby turns 6 months and mark it, so you have a rough start date to plan around.

Day 147 · 20 weeks 6 days old

How you will know your baby is ready for solids

Age is only part of the picture. The best guide is your own baby, and most show the signs of readiness together at about 6 months.

Your baby is likely ready when they can:

sit upright with a little support and hold their head steady open their mouth when food comes towards them, and show interest in food

move food from the front of the mouth to the back and swallow it, rather than pushing it straight back out with the tongue

reach for food, grab it and bring it to their mouth

That tongue-pushing reflex, sometimes called the tongue-thrust, is a good clue. While it is strong, most food ends up on the bib, a sign that your baby simply is not ready yet. It usually fades between about 4 and 6 months. Babies with health conditions or who were born very early may follow a different timeline, so ask your baby's doctor or nurse if you are unsure. Whatever the timing, milk stays your baby's main food for some months after the first spoon.

For your partner: Take over the next family meal with the baby at the table, propped safely on your lap, and watch for any of these signs, then share what you noticed.