21 Week Old Baby: Development, Milestones & Care Tips

Your 21-Week-Old Baby – Development, Milestones & Care

Medically Reviewed By
Dr. Gunjan Baweja (Paediatrician)
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At week-21, you will be seeing some exciting changes in your baby. It may be delightful for you to see your baby try to pull himself into a sitting position or attempt to crawl. Your baby is probably also responding to you or showing affection towards you. In a truly heartwarming moment, your baby might stretch out his arms to be lifted or may embrace you affectionately when you pick him up. During this week, most babies start imitating the actions and the words of the adults around him. Do you have a 21-week-old baby who has already shown some of these signs? Is yes, embrace yourself because there’s more to come! Read on to find out the developmental and growth milestones your 21-week-old baby is likely to show.

A 21-Week-Old Baby’s Development

A 21 week-old baby

Your baby, at 21 weeks, may display remarkable advances both physically and mentally. He will weigh around 14 to 16 pounds, and his hearing and vision will continue to improve. So, he will look in your direction when you call out his name. He may also begin to show a range of emotions like enjoyment, pleasure, anxiety, irritability, and boredom.

[Also Read: 5 Months Old Baby Development]

At week-21, your little one will also start displaying uneasiness due to separation from mother. Your baby could start crying when being passed on to someone else. If this is commonly happening with your baby, you may like to give adequate time to him to become familiar with the people who are new to him. Your baby will say his first words anytime now. He will try to duplicate the sounds that he hears most of the time.

Let’s take a look at some milestones your 21-week-old is most likely to achieve.

A 21-Week-Old Baby’s Milestones

Every baby develops at his own pace. So, the developmental milestones for each baby may be different. Here are some common milestones most 21-week-old babies undergo:

  • The taste buds are more developed by now. Your baby will be putting objects he can hold, into his mouth.
  • Some babies will be sitting by this week, although most babies may still need support while sitting up.
  • Your baby’s vision is constantly developing. He may be able to focus on moving and small-sized objects.
  • Your baby’s muscles are becoming stronger. He may be capable of rolling over to his side or flipping over for some tummy time.
  • Your baby may be adding new sounds to his typical babble, like a gurgle or a squeak. He may also be repeating sounds that he gets to hear around him.
  • Your baby is likely to laugh at or enjoy the funny faces and sounds you make.
  • Some babies begin teething by this week. You may see symptoms of teething such as excessive drooling, swollen gums, heightened irritability, etc.

[Also Read: 5 Months Old Baby Milestones]

Baby Feeding

You will be pleased to realise that your baby’s appetite is likely to increase. You may want to feed your baby in a quiet and peaceful environment as he is less likely to get distracted by his surroundings and may eat better. The feeding pattern, however, may change during this week. Your baby may simply drift from feeding into a nap. The number of feeds may reduce as the baby because the baby prefers to sleep during feeding time.

You may be tempted to introduce solids into your baby’s diet at week 21. But, it is essential that you continue feeding breast milk for a few months after weaning your baby onto solids. At this age, breast milk is enough to meet the nutritional requirements of the baby if he is fed on time and for the required number of times. There is no urgency to introduce solids as yet. It is quite common for babies to resist breast milk a little as they develop an extra preference for solids.

[Also Read: 5 Months Old Baby Food]


In spite of the sudden change in your 21-week-old baby’s sleep pattern, the sleep schedule might start getting regular. Here are some of the key points about the sleeping patterns your 21-week-old baby is more likely to have:

  • Your baby may not sleep throughout the night, but he may sleep for longer hours during the night.
  • Most babies wake up during the night because of thirst and hunger. Usually, breastfeeding your baby should help him settle down and get back to sleep.
  • However, his naps may become consolidated during this stage. He is more likely to take chunkier naps (around 45 minutes) instead of frequent small naps throughout the day.
  • It may not be a good idea to feed your baby too much before sleep time in the hope that he sleeps throughout the night. Overfeeding can cause colic and may lead to added wakefulness.
  • Sleep regression in 21-week-old babies is typical of this phase. If your baby has been sleeping well at night but unexpectedly begins waking up in the night or develops napping issues, he may be undergoing sleep regression due to growth spurts.

[Also Read: 5 Months Old Baby Sleep]

As your baby grows, you will need to keep changing the ways you care for him. During this week, your little one will need a little more attention and patience. What care must you take to ensure your baby is healthy, happy and prepared for the growth spurts in the next week? Let’s find out.

Care Tips for Your 21-Week-Old Baby

Follow these tips to ensure complete health and appropriate growth of your 21-week-old baby:

  • It is sensible to opt for ground settings or mattresses to prevent likely falls as your baby is now capable of rolling or flipping himself over.
  • You may like to offer soothing and safe teething toys or rings to your baby in case he is teething.
  • It is also desirable to sterilize his other toys as he is likely to put them in his mouth.
  • Keep an eye on your baby when he is playing with small objects or toys that can come loose as they turn out to be choking hazards.
  • Childproof your house and get rid of dangling cables or any other accessible objects that he is likely to pull down and hurt himself.
  • In case your baby is drooling too much keep a good supply of bibs handy.
  • To prevent diaper rash frequently change a spoiled diaper, clean the area properly and allow the baby to remain without diapers for some time every day.

[Also Read: 5 Months Old Baby Care]

Along with these care tips, you may want to ensure you stay updated with your baby’s vaccination schedule. Let’s discuss that as well.

Tests and Vaccinations

At 21 weeks, your baby is actually between immunisations. In case you have missed any of your baby’s 4-month immunisation vaccinations, you may want to schedule an appointment with your doctor on priority.

Another aspect of caring for your baby is to ensure he gets enough activities that build his motor and cognitive skills. In the next part of the article, we shall discuss some games and activities you must do with your little one.

Games and Activities

Games and activities bring about physical and mental development in your baby and help you bond well too. Here’s a list of some games and activities that you can enjoy with your baby.

  • Ground Time – Place a mat on the floor and let your baby enjoy an extended mat time. You may put him on his back first and let him roll and flip as much as he wants. Most babies, at 21 weeks, begin to explore and slowly start discovering their surroundings. An ample amount of supervised ground time can ensure he is safe and can explore most of his surroundings as compared to his time in the crib.
  • Sitting Up – Help your baby sit up in between his ground time. Place some pillows all around him to support him.
  • Trace the Direction of the Sound – Get a rattling/ musical toy and shake/ play it to make some sound. Keep doing it till he looks in the direction of the sound. Change the direction every time he traces where the sound is coming from. You may also do this activity when your baby is sitting up.
  • Sounds – To help your baby pick up sounds, talk to him as frequently as you can and ensure he is looking at you when you talk to him. Eventually, your baby will imitate the movement of your lips and even try to make similar sounds.
  • Keep Them Entertained – No, you don’t have to set up a performance for our little one to entertain every day. All you need to do is have enough bright-coloured toys, preferably something they can chew upon, musical toys, roly-poly toys, etc. that can hold your baby’s attention.
  • Baby Games – Play games like Peakaboo, Itsy Bitsy Spider, The Little Piggy, where is the toy/ object, etc. to continue building his skills.

[Also Read: 5 Months Old Baby Games and Activities]

Another important aspect of taking care of your little munchkin is to know when you must consult a doctor. It applies to all the health issues your baby could have before his next scheduled appointment.

When to Consult a Paediatrician?

At 21 weeks, your baby’s immunity is still not fully developed. Therefore, he may be vulnerable to the common cold and flu. You should consult a doctor if your baby has a runny nose, a fever or he is consistently crying. Sometimes, babies are prone to colic.  It is always better to follow the mother’s instinct and call/ consult a paediatrician if you feel something is amiss.


1. Is It Normal for My 21-Week-Old-Baby to Have Sleep Regression?

Yes, it’s normal for a 21-week-old baby to experience sleep regressions. These can be caused by developmental changes, teething, or other factors, leading to disrupted sleep patterns.

2. What Are Some Common Challenges Parents Face With a 21-week-old Baby?

Common challenges at this age include sleep disturbances, teething discomfort, separation anxiety, and adjusting to a baby’s evolving schedule and needs.

Your 21-week-old baby is now developing fast. The journey could be tiring, but it is sure to be exciting. Try and spend as much time as possible to bond with your baby as he will grow out of it soon. Remember, it is a wonderful time to enjoy the joys of motherhood!


1. Developmental Milestones; Pediatrics in Review; https://depts.washington.edu/dbpeds/Screening%20Tools/Devt%20Milestones%20Table%20(B-6y)%20PIR%20(Jan2016).msg.pdf

2. Your Baby’s Growth: 5 Months; Nemours Children Health; https://kidshealth.org/en/parents/growth-5mos.html

3. Let’s Talk About It: 5 Ways to Build Babies’ Language and Communication Skills from Birth; Zero To Three; https://www.zerotothree.org/resource/lets-talk-about-it-5-ways-to-build-babies-language-and-communication-skills-from-birth/

4. Age-Appropriate Vision Milestones; Stanford Medicine; https://www.stanfordchildrens.org/en/topic/default?id=age-appropriate-vision-milestones-90-P02305

5. Age-Appropriate Speech and Hearing Milestones; John Hopkins Medicine; https://www.hopkinsmedicine.org/health/conditions-and-diseases/hearing-loss/ageappropriate-speech-and-hearing-milestones

6. Separation anxiety; NHS UK; https://www.nhs.uk/conditions/baby/babys-development/behaviour/separation-anxiety/

7. Infant development: Milestones from 4 to 6 months; Mayo Clinic; https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/infant-development/art-20048178

8. Growth Spurts & Baby Growth Spurts; Cleveland Clinic; https://my.clevelandclinic.org/health/diseases/22070-growth-spurts

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