Breastfeeding Skin-to-Skin Helps Baby Build a Healthy Immune System

By Mary Marine – Antioch, California, USA

Have you ever wondered how breastfeeding skin-to-skin can help develop a healthy microbiome for both full-term and premature babies, even in the first few months of life? Immediate skin-to-skin contact after birth helps initiate breastfeeding. When the baby suckles, beneficial bacteria from the mother and her environment will colonize the infant’s microbiome and may help the infant digest food, while training the immune system to recognize bacterial allies and enemies. [1]

Photo credits: Stephanie Wernbo and Alex, by Sacha Blackburne

The “magical hour”

Several studies have found that healthy newborns placed on mother’s abdomen will use predictable movements to crawl to the breast. This moment is considered by many as the “magical hour” or “sensitive period” for them to bond. Research has identified nine predictable stages that begin with the baby being placed skin-to-skin and result in the infant’s self-attaching to the breast. During this period, the infant is moving his hands across the mother’s skin, and putting their fingers in their mouth, rooting, and sucking. Through this process, the baby is collecting healthy bacteria. [1] And this is how the infant develops a healthy immune system. A “Study found that 30% of babies’ beneficial bacteria come from their mothers’ milk and 10% come from the skin of mothers’ breasts.” [2]

Differences in care

There can be a big difference in the type of care a mother receives. Some mothers may be encouraged to have uninterrupted skin-to-skin contact straight after birth. All necessary care might be provided with the baby skin-to-skin, and medical staff may take care not to interrupt this magical time. For other mothers, the opportunity for skin-to-skin time with their baby might be delayed. This may be due to a scheduled c-section, emergency cesarean or because the baby needs special care. Even when skin-to-skin contact is delayed, the experience and the benefits are still there.

Photo credits: Teresa Pitman

The origin of skin-to-skin contact: kangaroo care

The practice of kangaroo care began in Colombia, South America. [3] The doctors caring for sick, premature babies, found that they had insufficient incubators. So instead, they gave the babies to their mothers to be held against their skin continuously, 24 hours a day. To their surprise, they found that these babies’ skin temperature, respiratory, heart and infection rates were better than those of some of the babies in incubators. 

When studies were published and hospitals heard about these benefits, skin-to-skin contact began to be implemented in healthcare facilities.
Today, holding the baby skin-to-skin intermittently has become part of the hospital routine in many countries, such as Sweden, Italy, Japan, England, and the United States.

Building a healthy microbiome

The microbiome is defined as all the microbiota (including bacteria, viruses, fungi and protozoa) present in certain specific environments, such as skin, vagina, breast, gut and mouth. For example, each woman has different microbes (yeast, E coli, etc.) in her vagina microbiota which, together with the microbiota from other specific environments, form the microbiome. We have more microbes in our bodies than cells. Each specific environment has its own microbiota because each area of the body needs a different microbiota to function.

In the infant, several things determine which microbiota are part of the microbiome.

  • Skin-to-skin contact helps build this healthy microbiome. [4] Several studies have found that premature infants that were held skin-to-skin have different bacteria in the oral and gut microbiome compared to preemies with no skin-to-skin contact. [4] These specialized microbiomes provide greater intestinal function, superior feeding tolerance, and greater immune stamina. They also protect preterm infants against devastating diseases, such as necrotizing enterocolitis (NEC) that affects the intestine.  
  • The diet of the infant, human milk or formula, contributes to which microbiota live in the microbiome. Just one feeding of formula can change the gut microbiota for the baby’s entire life. [5] 
  • The environment the infant has contact with can influence the microbiome. In the hospital setting, a baby may be exposed to the microbiota that can cause illness (known as hospital dysbiosis).
  • The method of delivery, c-section or vaginal birth, contributes significantly to the infant microbiome. Babies born by cesarean section are not exposed to the same microbiota because they have not passed through the vagina and had exposure to vaginal and gastrointestinal microbiota.
Photo credits: Carissa Munn

Skin-to-skin to initiate breastfeeding

Many studies have found that when the mother and baby have the opportunity to be skin-to-skin immediately after birth, they are more likely to begin and continue breastfeeding. [6] The skin-to-skin time increases the amount of the hormone oxytocin that the mother and baby produce, improving bonding and decreasing the stress response. The mother also experiences additional benefits from oxytocin, as it reduces the time it takes to deliver the placenta and decreases vaginal bleeding.

Human milk protects infants’ health

Human milk’s ability to protect the baby from illness is amazing. Human milk is known to protect infants from illnesses like NEC, pneumonia, and gastrointestinal illnesses, and to save lives, especially in premature babies.

A baby receives between 10,000 and 1,000,000 immune cells in human milk at each feeding and there are 10,000 to 13,000 cells per milliliter of milk. [7] If the baby is exclusively breastfed, he will receive relatively more immune cells than if he is fed with formula.  Babies who have received formula have a gut microbiome more similar to adults, in contrast to the healthier gut microbiome of babies that are exclusively breastfed. 

The number of immune cells in the mother’s body increases significantly if she is sick, and her body responds by increasing the number of immune cells in the milk. These immune cells can be produced even if she has no symptoms, and they protect her baby from pathogens.
The immune cells respond most significantly when it concerns a breast infection. When this occurs, the immune cells can increase, resulting in 95% more immune cells than when she is healthy. [7]  To a lesser extent, this also includes common cold, gastrointestinal illness, vaginal thrush, urinary, eye or ear infections.

In contrast, even when the infant is sick, their mother’s milk will increase immune cells in response to the early stages of an illness, such as when the only symptom is a fever. [7] This reinforces the idea of how connected mother and baby’s immunological systems are while breastfeeding.

How human milk works to provide antibodies

There are many components of human milk that seed and feed the baby’s immune system with healthy microbiota. There are likely more components that are yet to be discovered. The research on the infant microbiome is a quickly evolving area of study. 

  • Antibodies. The mammary cells include memory cells that store antibodies from prior infections. IgA is one type of immunoglobulin which is plentiful in the intestine and contains antibodies to microbes that the body has experienced in the past. These antibodies travel from the gut to the mammary glands and enter the milk supply. It is thought that antibodies might also be produced in response to bacteria going from the baby’s mouth into the mother’s breast. “Although this merits further investigation, the breast milk immune cell response to the infant’s infection highlights an underestimated component of the protective nature of breast milk.” [7]
  • Oligosaccharides. Human milk oligosaccharides (HMO) are an undigestible complex sugar. The baby’s intestine cannot digest this complex sugar; instead, its purpose is to feed the microbiota in babies’ microbiome. Researchers have learned that each mother has different HMOs and that each HMO is needed to feed a specific type of microbe. The HMOs are the third largest component of human milk after lactose and lipids. Colostrum contains 20-25g of HMOs per liter and mature milk has 5-20g of HMOs per liter. Colostrum includes relatively more immune cells to protect an immature immune system. [8] As an example of the differences between human milk and cow’s milk, over 100 types of oligosaccharides have been identified in humans while there are only 40 types in cows. [8]
Photo credits: Kimiyo Fardy

Skin-to-skin and breastfeeding as a lifelong protection

Holding babies skin-to-skin immediately after birth, and in the weeks to come, along with exclusive breastfeeding, can help seed and feed the healthy microbiota in their microbiome. [5] This leads to better health outcomes in infancy and later in life and can even affect future generations through epigenetics. Epigenetics is more simply explained by factors that can influence DNA. Sections of DNA, called genes, can be turned on or off by our environment and life experiences. This gene expression is independent of the underlying genes; the genes themselves are not changed. Thus, it is thought that experiences of kangaroo care and bonding may result in changes in gene expression that would stay with the child for a lifetime. Epigenetics is at least partially explaining why infants that were breastfed have fewer ear infections, less diarrheal disease, and less obesity and diabetes long term, among other chronic illnesses. [9]

If you aren’t able to hold your baby immediately after birth, then begin when you can. Mother’s and baby’s immune systems are amazingly connected. While skin-to-skin, the baby collects the healthy microbiota to build a strong immune system which forms a foundation for lifelong protection from illness. [7]

Mary Marine
has been a La Leche League (LLL) Leader for 25 years leading her Group and serving as LLL Professional Liaison in Northern California. The help she received with breastfeeding inspired her to become an LLL Leader. She also qualified as an IBCLC (International Board Certified Lactation Consultant) almost twenty years ago. She works in a county hospital and sees babies for newborn visits.
She lives with her husband, Greg, in Antioch, San Francisco Bay Area, California. She is the mother of Andrew, Christopher and Emily. 


1. Moossavi, S. Azad, M. Origins of human milk microbiota: new evidence and arising questions. Gut Microbes. November 2020; 9;12(1). DOI: 10.1080/19490976.2019.1667722

2. University of California – Los Angeles. Breast-feeding’s role in ‘seeding’ infant microbiome: Nearly one-third of beneficial bacteria in baby’s intestinal tract comes directly from mother’s milk. ScienceDaily. 8 May 2017.

3. Eichel, P. Kangaroo care: Expanding our practice to critically ill neonates. Newborn and Infant Nursing Reviews 2001; 1 (4): 224-228. DOI: 10.1053/nbin.2001.28101

4. Hendricks-Munoz, K.D. et al. Skin-to-Skin Care and the Development of the Preterm Infant Oral Microbiome. American Journal of Perinatology 2015; 32(13): 1205-1216. DOI: 10.1055/s-0035-1552941

5. Pannaraj, P.S. Li, F. Cerini, C. et al. Association Between Breast Milk Bacterial Communities and Establishment and Development of the Infant Gut Microbiome. JAMA Pediatr. 2017;171(7):647–654. DOI: 10.1001/jamapediatrics.2017.0378

6. Safari, K., Saeed, A.A., Hasan, S.S. et al. The effect of mother and newborn early skin-to-skin contact on initiation of breastfeeding, newborn temperature and duration of third stage of labor. International Breastfeeding Journal 2018; 13 (32).

7. Kakulas, F. Protective Cells in Breast Milk: For the Infant and the Mother? Splash! milk science update April 2013; International Milk Genomics Consortium.

8. Bode, L. Human milk oligosaccharides: Every baby needs a sugar mama. Glycobiology September 2012; 22(9): 1147–1162. DOI: 10.1093/glycob/cws074

9. Verduci, E. Banderali, G. Epigenetic Effects of Human Breast Milk.  Nutrients April 2014; 6(4): 1711–1724. DOI: 10.3390/nu6041711

Additional Resources

Harman, T. (Director). Breast Milk and the Infant Microbiome. Motion Picture: 2020.

Harman, T. The infant Microbiome and epigenetics. Microbirth online course. Alto Films: 2021.

Xiaomei Cong, et al. Gut Microbiome and Infant Health: Brain-Gut-Microbiota Axis and Host Genetic Factors. Journal Biology and Medicine September 2016; 89(3): 299–308.