3 week old baby: Development and milestones

As new parents, it might be difficult to get a decent night's rest when your precious 3 week old baby keeps crying. However, that's the only way your baby can communicate with you right now. You might feel exhausted and frustrated for now, but remember that your newborn won't stay small forever. Let's see what 3 week old baby development milestones are in store for your little one.

3 week old baby development

Physical Development

By the third week, your baby's skin should be peeling less and looking more plump, pink, and clear. Don't worry if your baby still has a cradle cap – that rough scaly dandruff-like skin on his scalp – because most of the time, it will go away on its own. It might look unsightly and uncomfortable, but it won't bother your newborn.

Your 3 week old baby would have also gained the weight he/she lost in his first week and should continue to gain weight at approximately 25 grams per day.

At this stage, your child’s median length and weight* should be as follows:

• Boys
  – Length: 49.8 cm (19.6 inches)
  – Weight: 3.3 kg (7.4lb)
• Girls
  – Length: 49.2 cm (19.4 inches)
  – Weight: 3.3kg (7.3lb)

And your child’s head circumference* should be:

• Boys: 34.5 cm (13.6 inches)
• Girls: 33.9 cm (13.3 inches)

As part of 3 week old baby development, his movements might be jerky and uncontrolled, which is normal for a newborn. This is because your baby's nervous system and muscle control still need time to mature. In time, when his muscles get stronger, his movements will become more and more fluid.

It is likely your baby will still be sleeping most of the time, just make sure to put him down on his back as that is the safest sleeping position. But during the short moments that he is awake, you can put him on his stomach to do some tummy time. This helps strengthen the neck muscles so they can push up to sit, roll over and crawl in the later months.

Cognitive Development

At three weeks, your baby is still trying to adjust to being outside of your womb. Loud noises will still startle him, trigger the waterworks and his Moro reflex. To help him calm down and feel more secure, you can always try swaddling him.

But did you know that you can also comfort your newborn by talking softly to him? Your little one can recognize songs or sounds he heard when he was still in your womb and mum's voice is one of the sounds he hears the most.

Another way for a baby to soothe themselves is by sucking. However, if you are nursing, you might want to wait until breastfeeding is well established before offering a pacifier so they can self-soothe. Even if you don't offer a pacifier, sucking on his own fingers will also help your baby to self-soothe.

Now it might seem as though all your baby does is feed, poop, sleep and repeat. But his brain is actually absorbing a lot of new things during his 3 week old baby development phase.

A good way to help him learn is to put your face in front of him during tummy time. Allow him to study your face and copy your lip movements. It might be very subtle, but if you watch him carefully enough you might actually notice him trying to copy you.

Nutrition and Health

Breastfeeding should be well established by now, and your breasts might be full and heavy with milk. There is no hard and fast rule about when to nurse your baby. At this age, feeding on demand is still best. The best way is to take cues from them and feed them whenever they need it, as babies typically know exactly how much food they need.

As long as your baby is latching well, satisfied, and gaining weight, then all is well. Check for lip and tongue ties if you are facing breastfeeding problems. You will still be able to breastfeed if your baby has a cleft lip or palate.

Also, remember to let baby drain each breast at each feed so you don't suffer from blocked ducts or mastitis. If for any reason you cannot breastfeed, then the only other suitable form of nourishment for your newborn is formula milk.

Your baby needs around 368.7 calories a day. Typically, the amount of breastmilk/formula milk for your baby at this stage is:

Breastmilk: 19.3-30.4 ounces/day
Formula: 16-24 ounces/day

If your baby was already having colic problems before this, then it might probably still be there during his 3 week old development phase. While it might be heartbreaking to see your little one so uncomfortable, this too will also pass. However, if it seems to be getting worse, his pediatrician might be able to offer some relief.

There are a few red flags that you can look out for, and make sure that your baby gets immediate medical attention:

1. Respiratory Distress: If you see rapid breathing, flaring of the nose, grunting while breathing or bluish skin that refuses to fade, your newborn might be having breathing difficulties.
2. Constant vomiting: It is normal for infants to spit up milk after feeds. But frequent vomiting is not. Be sure to mention this to the pediatrician. Your baby might be lactose intolerant or allergic to breast milk.
3. Oral Thrush: When the yeast starts manifesting in your baby’s mouth, it might end in oral thrush. Talk to your pediatrician and see if your little one needs a prescription for anti-fungal medication.

Vaccinations and common illnesses

This week, there are no vaccinations due for your baby. However remember that next week as your baby turns one month old, he/she will be due for the second dose of the Hepatitis B vaccine. To find out more about your baby's vaccination schedules, please click here.

Your baby’s immune system is still very immature making him/her very vulnerable to illnesses like the common cold. While it may not be as much of a big deal in older kids, in a newborn, a common cold could lead to severe consequences.

Therefore, it is important to make sure that whoever handles your baby is practicing strict hygiene which includes frequent hand-washing. Wear a mask if you have a cold or cough, and any other family members or friends with colds or who are sick should stay far away from the baby until they are better.

If your baby catches a common cold or other common illness, make sure that you bring him/her to the pediatrician immediately. At this stage, your baby is too young for any kind of home remedies.

Finally, it is important to make sure that nobody—including yourself—ever kisses your baby on his/her face, mouth, hands, or feet as this could potentially transmit the fatal HPV virus to your little one.

When to see a doctor?

If your baby:

• Seems to have trouble breathing, indicated by rapid breathing, flaring of the nose, grunting while breathing or bluish skin that refuses to fade.
• Vomits constantly.
• Has white patches on his/her tongue, which could indicate oral thrush.
• Has even a slight fever (over 37 degrees Celsius).
• Trouble latching on to your breasts.
• Has a bloated, highly distended stomach.

Newborn Care

Make sure you do not shake your baby especially when they won't stop crying. Your baby's neck is still very weak and cannot fully support his head. Shaking can cause your baby’s fragile brain to slide back and forth within his skull, possibly inflicting irreversible brain trauma also known as shaken baby syndrome.

Ensure that the room your newborn is sleeping in is of the right temperature. The ideal room temperature is 24ºC if you are using an air conditioner. At this temperature, their body is not fighting to stay cool or trying to warm up.

Here's another tip for moms with baby boys: Remember that when cool air hits your newborn's private parts, it might make him pee. So open his diaper slowly and with caution, so that you can catch the stream before it goes everywhere else!