The Development of a Baby's Stomach

The stomach is a very important organ. During the first days of life, it can only take a very small volume of milk.
The Development of a Baby's Stomach

Last update: 23 July, 2021

The development of a baby’s stomach, during its prenatal and postnatal periods, is very interesting. After babies are born, it’s important to bear in mind the size of this organ, because it’ll limit the volume of milk that babies can take.

What does the stomach do?

The stomach is a very important organ, which is a part of the digestive system. It’s located between the esophagus and the small intestine (duodenum). Besides, it contains an acid liquid, and its main function is to initiate the degradation of some macronutrients, such as proteins and carbohydrates.

All the food we eat goes through the stomach, which benefits digestion. Just as it happens with the rest of the organs, as time goes by, the stomach’s size and capacity grow progressively. And, this is what we’ll talk about next.

Newborn drinking breastmilk.

The development of a baby’s stomach inside the uterus

As in the case of other body parts, the foregut gives rise to the stomach. In fact, a part of the foregut dilates and forms a kind of a bag, which after some weeks, becomes the stomach.

Once the digestive tract becomes fully permeable, it gets in contact with the amniotic fluid. Did you know that your baby is constantly drinking this liquid? Besides the renal system, the integrity of this system relates to the development of certain diseases characterized by an increase or reduction of the liquid previously mentioned (polyhydramnios and oligohydramnios, respectively).

Read more: Polyhydramnios or Excess Amniotic Fluid

The development of a baby’s stomach after they’re born

When babies are born after full-term pregnancies (after the 37th week), their stomach is supposed to be ready to function properly. In fact, there’s a lot of emphasis on initiating breastfeeding immediately after the baby is born (early attachment).

During the first days of life, a baby’s stomach can be the size of a cherry or a nut. Therefore, they won’t have the ability to consume great amounts of milk. Once babies are one month old, their stomachs can reach the size of a tennis ball or an egg.

From a functional point of view, and as in the case of other organs, the stomach may not be fully prepared during the baby’s first days of life. The proper release of enzymes, proteins and hydrochloric acid may take several days to happen.

How much milk should I give my baby?

It’s quite logical to think that if a baby’s stomach is the size of a cherry during their first days of life, they won’t be able to receive all the milk your breasts will produce. However, this isn’t entirely true, because milk doesn’t stay in the stomach for a long period of time.

This is why you should be familiar with the concept of breastfeeding on demand. In fact, babies will express on their own (usually crying) their need to be fed, which can happen every few hours. As time goes by, they’ll adapt their eating habits, depending on their physical and social context. 

Continue reading: Prebiotics in Breast Milk, How Do They Work?

Should I try to give them more milk or another type of food?

Unless your pediatrician tells you to give them another type of food, babies don’t usually need anything but breast milk. This is because breast milk contains the main macro and micronutrients your baby needs. Furthermore, breast milk includes antibodies capable of protecting children against infections, while their immune system develops.

Fist days of life.

If you think your baby isn’t drinking enough milk in comparison to the amount you’re producing, don’t become excessively worried. What’s important is that they drink small amounts of milk several times a day. Besides, they should gain weight and increase in size during the first weeks.

However, if you pay attention to these details and you still think your baby has an eating problem, visit a pediatrician as soon as possible. Sometimes, certain problems are ignored at the moment of birth. So, remember that it’ll be always better to identify any kind of irregularity.

The stomach, a very important organ

It’s clear that the stomach is very important for your children’s proper growth and development. This is why obstetricians check its state during prenatal visits. And, that’s why unexpected problems are not very common once the baby is born. However, if you think your baby has an eating problem, tell your family doctor.


All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Carrascosa A. Crecimiento intrauterino: factores reguladores. Retraso de crecimiento intrauterino. An Pediatr 2003;58(Supl 2):55-73.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.