Babies (0-12 mos)


Child Development


How Long Is a Baby Considered a Newborn?

Newborn baby with mother in hospital

How Long Is a Baby Considered a Newborn?

Sleepless nights. That new baby smell. If you mention the word newborn to an experienced mom, all those sweet and complicated feelings will come rushing back. The newborn stage is challenging and wonderful all at once, but you may be wondering how long it lasts.

Babies are generally considered newborns until they're about two months old, although the exact definition of newborn varies. The infant stage typically comes after the newborn stage. However, the word infant can refer to any baby from birth to a year old.

Let's look at how long a baby is considered a newborn and what to expect during this stage.

Key Points

  • A newborn is generally classified as a baby who is one month old or younger, but some may consider babies newborns until three months of age.
  • During the newborn stage, a baby will begin to smile, grasp things, focus on specific objects, and hold their head up for brief periods of time.
  • Once your baby reaches one year of age, they're considered a toddler.

How Long Is the Newborn Stage?

When a baby is first born, the baby and new parents have a lot to get used to. Full-term newborns may meet developmental milestones right away while premature babies sometimes have to spend time getting stronger in the NICU before making strides developmentally. 

A newborn is a baby who was recently born, but how many weeks or months is considered recent can vary. The World Health Organization defines a newborn infant, or neonate, as a baby under 28 days old. Some organizations claim a baby is only a newborn until they’re 4 weeks old, while others say they’re considered a newborn until they’re 3 months old. 

How Many Weeks Is the Newborn Stage?

Newborn babies can seem like they’re changing all the time. With each passing day, they start to look a little different and get a little bigger. That’s part of the reason why moms tend to measure their baby’s age in weeks and then in months. For example, when asked how old their baby is, they will likely say 6 weeks old or 18 months old instead of 1 month or 1 year.

The newborn phase starts when a baby is born and in most cases, a baby is considered a newborn until they’re 6-8 weeks, or around 2 months old.

Newborn baby with father
Babies reach lots of different milestones in the newborn stage.

©Anna Kraynova/Shutterstock.com

What Are Developmental Milestones in the Newborn Stage?

You may think all newborn babies do is sleep. It’s true that they spend a lot of time sleeping in the first few weeks of their life, but they also learn a lot during the newborn phase. During the first 2 months of their life, newborns may start to:

  • Smile in a social way
  • Hold their head up for brief periods of time
  • Focus on specific objects
  • Grasp onto objects
  • Move their hands to their mouth

If you have specific concerns about any milestones, be sure to talk to your child’s pediatrician. But don’t fret if they’re not meeting every milestone right away. All babies are different; for some, catching up takes a little more time.

When Is a Baby Considered an Infant?

After the newborn phase comes the infant phase. Despite this distinction, infant can refer to any baby between birth and 1 year old. A lot can change in the first year of your baby’s life, but infant is a term that encompasses all those exciting changes.

It’s after the newborn period that babies really start to show their personalities more and are alert for longer periods of time. Starting at 2 months old, babies reach milestones such as putting their hands to their mouth and cooing.

What’s the Difference Between a Baby and an Infant?

No matter how old our kids get, we know they’ll always be our babies. But the word baby itself doesn’t always mean a newborn or an infant. It’s sometimes used as a way to describe all little ones who have yet to reach preschool age, including toddlers. However, there’s usually a distinction between babies and toddlers. According to the CDC, children between 1 and 3 years old are toddlers, and children between 3 and 5 years old are preschoolers.

How Long Are Babies in Newborn Diapers or Clothes?

There’s no denying that newborn-sized clothes and diapers are adorable. If you have a baby shower, you’ll likely receive a lot of newborn diapers and outfits and you may even be tempted to buy some newborn clothes for your little one as well. That’s okay! But be sure to keep in mind how quickly they may grow out of these clothes.

Since the newborn stage is so short, many babies outgrow the newborn size relatively quickly. If you have a larger baby, they may never fit into this size at all. When you’re purchasing clothes or diapers in a newborn size, be mindful that they may not fit in them for long, or at all, depending on their birth weight.

Typically, babies outgrow the newborn size after about a month. When you’re preparing for your baby’s arrival at home or packing your hospital bag, try packing newborn diapers and outfits, as well as the next size up. Even if your doctor or midwife has a prediction of how much your baby will weigh at birth, there’s no way to know for sure until your baby has arrived.

Are There Things I Shouldn't Do with a Newborn?

There are some precautions you're going to want to take with a newborn. This is one of the most vulnerable phases of a person's life. According to HealthShots, here are some things you should never do with a newborn:

  • Refrain from feeding your newborn cow's milk. A newborn is not able to handle cow's milk; it can actually cause intestinal problems for them. Stick to formula or breast milk.
  • Your baby doesn't need water for the first six months of their life. While this might sound odd at first, a baby will get all the water they need from breast milk.
  • Don't give your newborn solid food. Your baby isn't ready at this stage to digest solid food, so it could make them sick.
  • Don't try to stimulate them to poop. If your newborn seems to be struggling to poop, take them to a pedatrician.


The newborn stage is wonderful, exhausting, and fleeting. The days may be long but before you know it, your baby will no longer be considered a newborn. Even though the exact definition varies, babies are generally considered newborns up to 6-8 weeks old. Each new phase in your child’s life brings new challenges but watching them grow can be an adventure.

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