Spit-up! Bottles! Dirty diapers! If you’re a new parent, the amount of liquids passing through your newborn can seem overwhelming. Yet, if it’s your first time breastfeeding, it’s hard to know if your baby is getting enough to eat.

With their little body seemingly keeping nothing inside, you may begin to wonder if you’re over- or underfeeding your little one. To help you answer this question, we’ve got the facts you’ll need to understand the newborn stomach and what it can hold.

Size vs. volume

It’s important to note that there’s a difference between what a newborn’s stomach can hold vs. what it should hold (or what it normally holds).

When we talk about the “size” of their stomach, we’re actually talking about volume: how much milk (or colostrum) a baby comfortably takes when sucking at the breast.

When given formula early on, a baby might take more than that amount, but that’s not necessary and probably not healthy.

The size comparisons given below are good for visualizing approximately how much a baby should be offered or expected to take. Their stomach may or may not actually be that size and may not actually “grow” day to day.

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On day 1, your baby’s stomach is about the size of a pea or marble. A newborn can drink approximately 1 tablespoon at a time, so it’s OK that you’re probably only producing a limited amount of colostrum during feeds.

By day 3, your little one’s stomach has grown to be about the size of a walnut. This is usually enough to accommodate 0.5 to 1 ounce (oz) of liquids.

If you’re breastfeeding, you might find yourself engorged around this time, and your breastmilk will probably start to become whiter and more liquid. This is called transitional milk, and you can read more about it below.

By the time your baby is 10 days old, their stomach is probably the size of a golf ball. After 10 days, your baby is ready for 1.5 to 2 oz of liquid at a feed.

If everything is going well with feeding, your baby should be nearing their birth weight again by now.

Believe it or not, your breasts have been developing colostrum since you were 12 to 18 weeks pregnant! Even if you don’t intend to breastfeed, your breasts will still develop colostrum, so you should talk to your provider about how best to handle this.

When a baby is first born, they usually drink about an ounce of colostrum in the first 24 hours after birth, over the course of several feeds.

They may also want to spend a lot of time sucking at the breast, which is helpful for the development of your breastmilk supply.

If it seems that all your baby wants to do is eat, it doesn’t necessarily mean that your little one isn’t getting enough. It’s totally natural and signals to your body to make more milk.

It’s also normal for a baby to want to sleep a lot in the first 24 hours. A healthy newborn often gets in a good first feeding in the first hour or two of life.

Colostrum will begin changing to transitional milk approximately 2 to 5 days after giving birth. Transitional milk will be more voluminous than colostrum and may appear like whole milk.

By around 10 to 14 days after birth, you should be on your way to producing mature milk. Mature milk is divided into a watery foremilk and a fattier hindmilk.

Mature milk’s composition will change daily based on your baby’s specific needs. But if you would like to increase or decrease the amount you’re producing, it’s important to remember that breasts work on a supply and demand theory.

The more frequently you drain them, the more breastmilk they’ll produce.

With formula, it’s important to monitor how many ounces your little one is consuming as there is a chance of overfeeding your baby.

Remember, the stomach is an organ that can expand, which is why frequent spitting up can sometimes be a sign that a baby is eating too much.

Signs of overfeeding might include:

  • fussiness after feeding
  • frequent vomiting
  • gassiness
  • diarrhea

The American Academy of Pediatrics (AAP) recommends against propping the baby’s bottle, as this can lead to overfeeding.

Instead, an adult should be actively involved in the bottle feeding, holding the baby upright, keeping the bottle horizontal, and watching for cues that the baby is no longer interested.

When deciding whether to use formula, it’s important to note that supplementing breastfeeding with formula or ending breastfeeding before the recommended timeline can have effects later on. It’s been shown to contribute to obesity in childhood and adolescence as well as obesity and cardiovascular disease in adulthood.

While the World Health Organization (WHO) recommends breastfeeding exclusively for the first 6 months, this isn’t always possible or desired.

Many experts recommend breastfeeding exclusively for at least the first 3 to 4 weeks to help establish your breastmilk supply and ensure your baby’s comfort with feeding at the breast.

There are, however, times that supplementing with formula may be medically indicated, such as when your baby isn’t gaining weight adequately or needs additional hydration to help with jaundice.

Formula may also make sense if you’re returning to work and having trouble producing an appropriate amount of milk. Your doctor can provide guidance around choosing a formula and how much to feed your baby.

Your baby’s stomach is tiny. It’s normal to feel some concern about the amount of food they do (or don’t!) seem to be eating. But chances are, if they’re a breastfed baby, they aren’t overeating.

Remember, your little one won’t need a lot of food, but they’ll need it frequently. It’s important to make sure that you’re watching for signs of hunger, especially when not much is going in during each feeding,

You’ll also want to keep an eye out for appropriate weight gain as well as sufficient amounts of poop and pee to indicate that they’re getting enough.