Infant Microbiome: What Is It And Why Does It Matter?

Key Points:

1. The microbiome consists of beneficial microbes important for health; babies are born without one, making them vulnerable.
2. Babies' unique microbiome develops early, affected by birth method and breastfeeding, crucial for health and immunity.
3. Vaginal birth and skin-to-skin contact introduce the mother's microbiome to the baby, helping develop their own and reducing allergy risks.
4. Direct breastfeeding is best for the baby's microbiome; the mother's diet impacts both her and her baby's gut health.

Most of us have heard about the gut microbiome, but other than knowing it’s a group of ‘good’ bacteria, we don’t really understand much about it.  Though it seems a population of healthy microbes which live in our bodies as well as on our skin, helps us in a myriad of ways to stay healthy and live well.

As adults, we’ve had years of exposure to the trillions of bacteria which form our own, unique microbiome, though babies are born with essentially no microbiome of their own. And this, in combination with their immature immune system is what contributes to their vulnerability.

What is the microbiome?

The microbiome is the collection of all the microbes including fungi, viruses, bacteria, fungi and protozoa living on and inside our body. An adult’s microbiome may weigh up 2kgs.  And although you can’t see your own microbiome – it would take a powerful microscope to view even a sample of it, appreciate your own unique microbiome for all the wonderful work it’s doing.  

What does the microbiome do?

The microbiome plays an important role in maintaining good health, including gut function, mental health, immunity and digestion. Our gut microbiome also helps to digest our food and extract nutrients and compounds to support good health.

There’s really no comparison!

Each individual adult has their own unique colony of healthy bacteria living in their gut. These are constantly being reproduced and evolving as a result of our diet and our living conditions.  It’s estimated that a healthy adult has between 500-1000 different species of gut bacteria, which are constantly interacting with our nervous system, regulating our immune system, producing unique vitamins, e.g. Vitamin K and even influencing our mental health and our moods.   

Researchers have found that a healthy microbiome also helps to prevent a range of auto-immune diseases such as irritable bowel disease and type 1 diabetes.  It also helps to reduce the risk of developing asthma and allergies and becoming obese.

Even in the earliest days of life, this ‘switching on’ of healthy bacterial growth, helps our babies to stay well.

What we know to be true about the infant microbiome

The image of thousands of bugs coming even close to our precious babies is enough to keep loving parents awake at night. And of course, not all bacteria are healthy, some are positively harmful. Research has shown that the development of a healthy microbiome is essential for normal development and a range of health related benefits.

1. During pregnancy, the baby is in a sterile environment, though it is still being influenced by the mother’s own unique microbiome. All of the baby’s needs are being managed by the mother and the placenta, so what she does and what she eats has a powerful influence on the growing baby. 
2. After birth and in the first few months of a baby’s life, their own unique microbiome starts to form. Researchers are finding that this is a critical window of time for babies to develop their own unique colony of beneficial organisms.
3. We know that the first three years of a child’s life is significant in terms of their social and emotional development. It now seems that the first three years is also important for a child to be exposed to a diverse range of ‘good’ bacteria which will support their long term health, immunity and prevention from disease.
4. Evidence has shown that families actually ‘pass on’ their own unique microbiome, reducing or increasing susceptibility to some infectious or autoimmune diseases.

What affects healthy microbiome development in babies?

Starting from birth, babies are exposed to the external environment and a range of bacterial ecosystems. This helps them to build immunity.  Even when they’re in utero, babies are exposed to their mother’s oral and gut microbiome, which has long term consequences for the baby’s health.

It seems that intentionally insulating our babies from germs may not be a good thing. There’s a balance between having a reasonably clean environment and being too fastidious. 

You are what you eat  

During pregnancy, a mother’s microbiome population changes as her pregnancy advances, so more nutrition is drawn from the food she eats.

Type of birth matters

During a vaginal birth, the baby is exposed to the mother’s vaginal bacteria. This doesn’t happen when babies are born via caesarean section, where they are lifted out of the sterile uterus into a sterile field in the operating theatre. But this is where the importance of skin-to-skin contact comes into play.

As soon as the baby is lifted (or transferred) onto the mother’s chest or breast, they are exposed to the bacteria which colonise her skin.  Her hands, her breath, kissing her baby and perhaps, even her tears are all ways the baby’s body is open to this bacterial transference.

Some studies have found that babies born via caesarean section are more vulnerable to developing food allergies and asthma, than babies born vaginally.  It also seems there is a degree of protection for babies when a mother experiences labour after her waters have broken, even if she does progress to having a caesarean section birth, when compared with babies born via an elective, or planned caesarean.

The importance of breastfeeding

Breastfeeding is another significant means of exposure to healthy microbes which colonise the baby’s mouth and gut. Breast milk contains HMOs - human milk oligosaccharides - which feed specific, beneficial bacteria in the baby’s gut. A similar process happens when we eat foods rich in probiotics.

Breast milk also contains other healthy bacteria which support microbiome development. Exclusive breastfeeding is recommended for the first six months of a baby’s life when other solid foods are introduced to compliment breast milk.

Try to breastfeed your baby directly, rather than offering expressed breast milk. They will have more opportunity for exposure to the ‘good’ bacteria in breast milk and less risk of contamination with ‘unhealthy’ bacteria when it’s directly from breast to baby’s mouth.

Stay well

Ideally, mothers should try to avoid taking antibiotics themselves or giving their baby antibiotics, unless they’re really necessary of course.

Eat a healthy diet, rich in fruits, vegetables, legumes and foods which will support your own gut health as well as influence your baby’s gut microbiome. Yoghurt, kimchi (salted and fermented vegetables) and kefir (a fermented milk drink) are all good sources of healthy bacteria.

It’s bath time!

Avoid overdoing it when it comes to bathing your baby and don’t use anti-bacterial soaps or bath wash unless you’ve been advised to by a healthcare professional.    

Key messages about infant microbiome

1. A mother’s diet during pregnancy has an influence on her own, as well as her baby’s forming gut microbiome.
2. A healthy range of microbes colonising on and within our body helps with digestion, boosting immunity, protection against certain diseases and vitamin production.
3. Research is still unfolding into the human microbiome, though currently, most of the findings are positive.
4. Vaginal birth, skin-to-skin contact and breastfeeding are all protective factors in supporting healthy microbiome development in babies.

About the Author: Jane Barry - Your Health Content Expert

Jane Barry is a registered nurse, midwife, and child health nurse with a passion for combining clinical expertise and writing. She has nearly 30 years of specialist experience in child health nursing and holds a Bachelor's Degree in Applied Science (Nursing). Jane specialises in women’s health, parenting, pregnancy, babies and maternity care, child health, nutrition, feeding, teething, and dental health issues.

An active member of AHPRA, The Australasian Medical Writer’s Association, Health Writer Hub, and the Australian College of Children and Young People’s Nurses, Jane Barry delivers health content with professionalism and clarity.

Sources

• FF_Microbiome.pdf (washington.edu)
• https://microbiome.org.au
• What you eat while pregnant may affect your baby’s gut (biomedcentral.com)