Baby’s Digestive System: From Womb To Infancy

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The placenta provides all the nourishment to the fetus in the womb. Once born, the baby’s digestive system becomes responsible for this process. The infant’s digestive system develops gradually while receiving nourishment from breast milk, the baby’s first food.

Once the baby is older than six months, their digestive system is mature enough to process solid food items and receive nourishment from them. Keep reading to know the various parts and attributes of a baby’s digestive system.

Baby’s Digestive System: From Womb To Birth

The digestive system is responsible for breaking large food molecules into smaller ones. The broken molecules ensure adequate absorption of nutrients and the development of healthy bacteria in the gut (1).

Fetal digestive system (in the womb)

The gastrointestinal tract starts growing from the third week of gestation. By the fourth week, three distinct regions of the gut extend across the length of the embryo. These regions ultimately form different components of the gastrointestinal tract (2).

A fetal digestive system includes the mouth, esophagus, salivary glands, stomach, small intestine, large intestine, and rectum. All these digestive system parts develop in the womb itself. However, they stay functionally ineffectual until birth. This digestive system undergoes tremendous growth and functional maturation throughout pregnancy.

Newborn digestive system (full-term birth)

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At full-term birth, the entire digestive system is ready to operate independently. While descending through the birth canal, the neonate system gets microbes via the vaginal microflora (3). It is a crucial occurrence as it contributes to the development of the newborn’s digestive system, including the intestinal microbial ecosystem.

This development continues as the newborn baby begins breastfeeding. For their first feed, most of the breastfed babies receive colostrum, the first milk produced after birth. Colostrum is rich in antibodies and nutrients such as fat, vitamins, and minerals that help the newborn baby grow (4). Besides, it helps in the development of the complex microorganism population that thrives in the baby’s digestive tract (5).

The changes in the baby’s body could cause a 7% loss of their birth weight within a few days (6). However, this weight loss is benign.

Newborn digestive system (preterm birth)

A premature birth leads to structural and functional differences between the digestive system of a preterm and full-term baby. A preterm gut is immature and incapable of most functions a term gut can perform. A premature infant may not be ready to digest human milk, particularly the proteins present in it (7). Complete digestion of milk requires digestive juices such as gastric juice and pancreatic juice along with digestive enzymes, such as amylaseⁱX A digestive enzyme, primarily secreted by the pancreas and salivary glands, that breaks down carbohydrates into simple sugar. to digest starches and pancreatic lipaseⁱXEnzyme secreted by the pancreas that breaks down fat in food to be absorbed by the intestines. for digestion of lipids. For these reasons, right after birth, a full-term infant is advised to breastfeed. However, this may not be the case with a preterm baby who needs time to be able to do the complex job of tolerating milk feeds.

Most babies, both preterm and full-term, spit up frequently due to the immature digestive system or a weak and immature lower esophageal sphincterⁱXRing of muscles in the esophagus that controls the passage of food and liquid through the esophagus and prevents regurgitation. (8). However, it could also happen due to some digestive tract lining issues.

Did you know?

Necrotizing enterocolitis is one of the most common but life-threatening intestinal disorders in premature babies. It is characterized by inflammation of the intestinal tissue (16).

The Digestive Tract Lining Tissue

An infant’s digestive tract lining is a layer of mucus that protects the digestive tract from harmful microbes and other contaminants present in the food. At the time of birth, this lining is very thin and immature, which can increase the risk of digestive lining issues, such as inflammation and infections.

These gastrointestinal infections are dealt by antibodies present in breast milk, and this continues until the digestive mucosal liningⁱXLayer of mucus lining the gastrointestinal tract that defends against bacteria, toxins, and other kinds of harmful substances. becomes mature. While breast milk is helping the digestive tract develop its lining, it also helps in the development of gut microbiotaⁱXThe population of microorganisms in the digestive tract. . This is the reason why a mother’s dietary intake while breastfeeding should be healthy and planned.

In general, a baby’s digestive system continues to grow through the first two years of their life. This progression also has a direct link with the development of the baby’s immune system. Thus, the nutritional composition of the baby’s diet in the early years of life is considered crucial.

Why Should Solids Be Avoided Until Six Months?

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Breastfed or formula-fed infants can usually start solids by the age of six months. However, the right age may vary depending on the signs of readiness (9). Until then, solid foods are avoided because of the following reasons (10):

• The gag reflex is underdeveloped, thus posing the risk of choking.

• The frequency of breastfeeding would reduce, which can lead to a compromise in the intake of vital nutrients from breast milk.

• Proper digestion of solids would be difficult as the enzymes digesting carbohydrates develop at around six to seven months of age. The bile saltsⁱXBile acids produced by the liver from cholesterol to aid in the digestion of fats and fat-soluble vitamins. and gastric lipase that help digest fat reach optimum levels between the ages of six and nine months.

• The larger food molecules might pass through the small intestine directly into the bloodstream as infants under six months have a permeable gut. This scenario could lead to gastrointestinal tract ailments and possible allergies (11).

Be watchful

Introducing solids before six months may increase the infant’s risk of developing diseases such as diarrhea. Diarrhea may lead to weakness and weight loss and, if left untreated, may also be fatal (17).

How To Support Your Baby’s Digestive Learning Curve?

The changes in the digestive system are rapid. Parents could take a few measures to support these developments.

1. Exclusive breastfeeding: Several research studies have shown the breastfed infants have better digestive, respiratory, and overall health due to the complex nutritional composition of breast milk (12). Therefore, mothers should exclusively breastfeed for six months and continue breastfeeding, if possible, for up to two years. The World Health Organization estimates that only 44% of infants between the ages of zero and six months are exclusively breastfed.

2. Introduction of solid foods: You can support your baby’s gastrointestinal development by gradually introducing solids at around six months of age. As a general practice, you could do the following:
   

   Image: IStock

• Introduce one food at a time with easy-to-digest foods introduced first. Soft fruits such as apple, pureed meat, poultry, beans, and iron-fortified cereals are some options to try (13).

• As you add new food, wait three to five days, and watch if the food causes digestive discomfort to the baby. This way, you can identify a potential allergen.

• Begin feeding solids in cooked, mashed, or pureed form. As the baby grows and develops motor skills, you may transit to soft cooked food pieces (finger foods) by about nine months

• Try to add a variety of foods to your baby’s diet right from the start so that they may reap the benefits of these foods in the long run.

• Adjust the quantity of solid food to account for the consumption of breast milk or formula. Breast milk takes approximately an hour and a half to digest, while formula may take four to five hours.

3. Practice hygiene: Hygiene measures while preparing baby food can reduce the risk of microbial and elemental contamination and prevent tummy troubles.
   

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Infographic: Ways To Support Your Baby’s Developing Digestive System

A baby’s digestive system matures over time. It is crucial to know the timelines to decide what’s best to feed a baby. It is also important to look out for food sensitivities as you introduce solids. The infographic below takes you through some key measures to support your baby’s developing digestive system.

Illustration: Momjunction Design Team

If your baby is feeling uncomfortable due to some digestive issues you should check out this video. In this video, you will learn what the probable causes of this discomfort could be and how you can help ease such discomfort.

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Dr. Shashidhar AMD

Dr. Shashidhar is a qualified pediatrician and neonatologist with 14 years of experience in pediatrics and neonatology. Currently, he is practicing at St John's Medical College and Tiny Tots Clinic in Koramangala, Bangalore, and is a part of an accomplished team taking care of preterm and sick newborns until discharge and follow up. He is a teacher at various levels...more

Swati PatwalM.Sc. (Food & Nutrition), MBA

Swati Patwal is a clinical nutritionist, a Certified Diabetes Educator (CDE) and a toddler mom with more than a decade of experience in diverse fields of nutrition. She started her career as a CSR project coordinator for a healthy eating and active lifestyle project catering to school children. Then she worked as a nutrition faculty and clinical nutrition coach in...more

Rohit GarooBSc, MBA

Rohit Garoo is a writer-turned-editor with over 9 years of experience in content writing, editing, and content marketing. He did his bachelors in Science at St. Xavier's College, Hyderabad, and masters in Business Administration at Osmania University. Also, he holds a certificate in Developmental Psychology from The University of Queensland and loves to expand his knowledge through certifications in various...more

Ghazia ShahMSc, MA, BEd

Ghazia is a scientist-turned-writer with three years of research experience in Cancer Biology. She did her masters degree in Biotechnology at the University of Kashmir and bachelors in Education at the same university. Ghazia then delved deeper into the science of language with a masters in English. With a Functional English certificate from Indira Gandhi National Open University (IGNOU), she...more