Your 3-Week-Old Baby’s Development

Major milestones and everyday tips for your baby at 3 weeks

Parenting a 3-week-old baby can be the start of a big shift for you and your little one. At 3 weeks old, your baby will start to become a lot more alert and active. They may even seem like an entirely different baby than the one you brought home. Just when you were getting the hang of things, your baby changes yet again. Welcome to parenthood!

As your baby grows, it is important for you to know what to expect from each stage of life and to best prepare yourself for those changes. Here’s what you can expect from your 3-week-old.

3-Week-Old Baby
Illustration by Joshua Seong, Verywell

Your Growing Baby

Your baby will continue to grow a lot during this month, at a rate of gaining 2⁄3 of an ounce (20–30 grams) per day and putting on 1.5–2 inches (4.5–5 centimeters) by the end of the first month of life. By 2.5 weeks old, the average male baby will have a head circumference of 39.21 centimeters, while the average head circumference for female babies is 37.97 centimeters.

Developmental Milestones

Mind & Body

Your 3-week-old baby is getting stronger and changing every single day. They can lift their head up for a few seconds and may even turn their head side from side, especially to follow you or a caregiver as you move away or around the room. Your little one will love to watch you and may look like they are carefully studying your facial expressions or listening to you chat. Although they can't understand your words yet, talking out loud to your baby is great for language development, even at this early age.

As your little one grows, there may be some “growing pains” with more crying or fussiness than in previous weeks, especially in the evening. Some babies might also develop colic at this age. Here's what you can do to help:

  • Introduce a calming evening routine: You might start a routine that involves a gentle bath, followed by infant massage with safe baby lotion. If your baby is gassy, you can also follow infant massage techniques for relieving excessive gas.
  • Don’t use gripe water: While gripe water is an old wives’ remedy for easing gas and irritability, studies have shown that gripe water is not effective and may actually harm your baby.
  • Pay attention to your diet: If you’re breastfeeding, it might be possible that something in your diet could upset your baby’s stomach. If your baby is fussy after feedings, spitting up more than normal, or has a lot of gas, it might be helpful to keep track of what you are eating to determine if there is a link. Some foods like chocolate, caffeine, or seeded fruit like raspberries can lead to digestive issues with babies.
  • Put the baby down in a safe spot: Every now and then, you just need a break from a baby who is crying. If they've been fed, changed, and you are reaching your breaking point, don’t push past it. If you feel like you need a break, take one. Put your baby down in the crib for a few minutes while you take a deep breath. If you ever feel like shaking your baby, put the baby down and walk away. Every parent needs a break from time to time and a baby who has colic or fussy periods can be very challenging. 

    When to Be Concerned

    It can be difficult to distinguish if your baby is experiencing “normal” fussiness or if there is something else wrong. If your baby is displaying signs of excessive spit-up, is projectile vomiting, has blood in the stools, is not gaining weight, or is refusing to eat, you should seek medical attention. Colic does tend to start around 3 weeks old, so you can keep track of how long your baby is crying and when it tends to happen. In babies with colic, there could be periods of crying that last two to three hours per day, especially at night.

    Try These Easy Ways to Calm a Colic Baby

    A Day in the Life

    At 3 weeks old, your baby's daily routine should include regular tummy time. You might not need to put your baby on a strict schedule, just look for small pockets in the day to introduce tummy time. Your little one might not like it at first, but it is an important way to start building their neck muscles to encourage proper development. Keep it simple by placing your baby on the nursery rug or blanket on the floor or using a breastfeeding pillow. Just be sure to always stay near your baby and never leave them unsupervised during tummy time.

    If this is your first baby, by three weeks, you might be wondering what exactly you “do” with a baby. Sure, you can stare at them all day (and night) and change a lot of diapers, but you might both need a little more stimulation during the day. Three weeks is a great time to try out some new activities together, such as:

    Baby Care Basics

    If your baby was circumcised at birth, you can continue to clean the penis with normal soap and water. By this age, the circumcision site should be healed, so if you notice any redness, pus, or drainage, be sure to have it looked at by a doctor. If your infant is uncircumcised or has any foreskin left on the penis, you should never force the foreskin down. A male’s foreskin will retract naturally somewhere by the age of 5, but can take longer in some cases. Until then, just clean the head of the penis as you would any other part of the body.

    For baby girls, you may have noticed the occasional vaginal discharge during diaper changes or bath time in the past few weeks. It can look clear, white, or blood-tinged in appearance and although it may be alarming at first, it is normal. Vaginal discharge can be caused by the mother’s hormones during pregnancy, delivery, and breast milk production, and it should dissipate around this time. If you notice discharge that lasts longer than that, discuss it with your baby’s doctor.

    The mother’s hormones may also cause your baby to look like they have enlarged breasts in the newborn days. By this week, however, that swelling should go down.  

    At this time, your baby might develop a clogged tear duct, called lacrimal duct obstruction, in one or both of their eyes. You might not even realize it until you notice watery or green drainage stuck near their eye. Clogged ducts are common in babies and will often resolve on their own by the time your baby turns one. However, in some cases, they can become infected. Help clear your baby’s tear duct by applying a warm washcloth compress to clean off the drainage and help empty the duct.

    You may also notice new skin problems for your 3-week-old baby, such as rashes, baby acne (no, this isn’t the teenage years, yet!), or “scales” on their scalp, called cradle cap. Many of the skin irritations at this age are minor and normal, but keep your little one comfortable by trying the following:

    • Avoid harsh soaps in the bath.
    • Reduce bathing times to once or twice a week.
    • Use gentle, baby-safe detergent and fabric softeners.
    • Monitor if symptoms get worse with changes in skin care products and try to avoid anything that irritates your baby’s skin.
    • Don’t “pop” or squeeze at your baby’s blemishes—they will resolve on their own with time.
    • Use a baby comb or brush to gently loosen the scales of cradle cap while in the bath.
    • Let your baby go without clothes or even diapers for an hour or two in the house, especially in the summer if they are experiencing heat or diaper rash.

    Feeding & Nutrition

    At 3 weeks old, your little one should be old enough to try a pacifier if you would like to introduce one. Some doctors advise parents to avoid using pacifiers early on in their baby’s life as breastfeeding begins to prevent nipple confusion and ensure that a mother’s milk supply is properly established—which it should be by this time. 

    The American Academy of Pediatrics recommends trying it because studies have shown that pacifier use is associated with a lower incidence of SIDS. But, remember, there is no right or wrong decision about using a pacifier with your baby, so it’s a personal choice. Not all babies will necessarily want to use a pacifier, so never force it. 

    Although newborn babies will grow at tremendous rates the entire first year, you may notice a slight decrease in feeding frequency from last week. Remember, your baby went through a growth spurt in week two. This week, your baby should still be fed on demand and nursing sessions can last anywhere from 20 minutes to a full hour.

    If you're breastfeeding, it’s also very important to continue administering vitamin D supplements to your baby every day. Your pediatrician or the hospital should have supplied you with free vitamin D drops, but if they did not, ask your doctor or call up the birthing unit to ask. Vitamin D supplements are so important to your newborn baby if you are breastfeeding because breast milk does not naturally contain the adequate levels of vitamin D your baby needs. Vitamin D deficiency can be extremely serious for newborn babies, especially as their bones continue to grow.

    By week three, if you are nursing and plan to feed your baby from a bottle at all, whether to return to work or simply have a bottle as an option, you may want to start pumping to establish a frozen breast milk supply. Consider pumping after you feed your baby, but only if you are sure they have finished eating completely.

    The end of a breast milk session contains a type of milk called hindmilk, which is a different composition than the milk at the beginning of a feed. Hindmilk contains a higher fat composition and it’s important that your baby finish emptying your breast completely before you pump. If pumping after a feeding doesn’t work for you, you could also try incorporating a pumping session into your day, such as in the early afternoon when your baby might be napping. Use freezer-safe breast milk storage and label all of your breast milk once it's stored so you know when it was pumped.

    How Long Should a Baby Breastfeed at Each Feeding?

    Sleep

    This week, your baby should still be sleeping the majority of the time, around 16-18 hours per day. You can continue to try to introduce sleep cues, such as bath time or reading baby books, but establishing a strict sleep schedule is probably not the best idea just yet. Continue to let your baby lead the way for sleep during these first few weeks.

    Health & Safety

    Many 3-week-old babies enjoy being swaddled to calm down or go to sleep. If you choose to swaddle your little one, it’s important to be aware of the American Academy of Pediatrician’s safe sleep guidelines, which state that there is a high risk of SIDS for infants who are swaddled and then placed on their stomachs or sides.

    If you swaddle your 3-week-old, make sure you only lay them down on their backs to go to sleep. The AAP also suggests that parents swaddle snuggly around the chest and looser around the hips to prevent making any cases of hip dysplasia worse. But once your baby starts rolling, the AAP says it’s time to stop swaddling. At this age, your baby shouldn’t be quite ready to roll yet, but start keeping an eye out during nap times.

    Any lingering jaundice that your baby had should be resolved by now. If your baby appears yellow or has yellowing of the whites of the eye, skin, or appears lethargic, you should consult your pediatrician.

    Must Knows

    As you go through this third week with your baby, keep these tips in mind:

    • Give yourself a break: Parenting a 3-week-old baby can be challenging. At this stage, your little one might be more active, alert, and may be experiencing more fussy periods and tears. It is important to give yourself breaks and to have a plan for times when you feel overwhelmed. When in doubt, put your baby down in a safe place and walk away if you need a time-out for a few minutes.
    • Continue to take care of yourself: You’re most likely feeling stronger, but your body still needs plenty of rest and nutrients to continue healing. Drink a lot of water and keep taking your prenatal vitamins to stay nourished.
    • Make sure your baby is getting vitamin D: If you’re breastfeeding, you will need to give your baby vitamin D supplements. You can find these at the store or through your baby’s doctor. Formula-fed babies will receive adequate levels of vitamin D in their formula, but breastfed babies require supplementation because vitamin D is not found in breast milk.
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