Baby’s Immune System

This essential defense grows over time, but gets a jumpstart from mom
July 15, 2019 Updated: July 15, 2019

As with all other organs and systems in their bodies, newborns’ immune systems are not fully developed at birth. Rather, their immunity—a protective function consisting of cells, proteins, and organs—grows and strengthens with time. With each new day, this immune system strives to keep them safe from the countless pathogens in their environment.

At birth, a baby’s immune system is still quite weak and sensitive. Given its fragility, nature has compensated for this by endowing mothers with the ability to transfer immunity to their baby (called passive immunity) by way of antibodies through breast milk. A mother’s breast milk is filled with protective immunoglobulins that work to fight off bacteria and viruses that could be harmful to the baby. This is why breastfed babies get sick much less often than formula-fed babies.

Immunoglobulins survive the digestive tract because they are packaged within a protective substance that allows them to survive the stomach environment and get to the intestinal tract, at which point they adhere to the lining or are absorbed. By remaining in the digestive tract, immunoglobulins help prevent the growth of bacteria that can be dangerous to a baby’s health.

Interestingly, during , a mother also passes on helpful antibodies, particularly IgG, through the placenta, which remain with the baby for the first few months of life. From colostrum—mother’s first milk—onward, breast milk is filled with highly beneficial antibodies that a mother’s own body has developed in response to her region’s specific pathogens.

A child’s immune system will start to develop on its own at about 2 to 3 months of age. At this point, the antibodies that the mother has conferred start to decline. A baby’s immune system begins to grow and develop when it comes into contact with bacteria, viruses, and fungi. The immune system can now wage a counterattack against the invaders. By 1 year of age, a baby will have developed its immune system significantly, although not entirely. Some experts suggest that an immune system is not fully developed until a child is approximately 12 to 14 years old. At this time, the child has reached adult levels of antibody formation.

Strategies to Boost Baby’s Immunity

  • Breastfeed for as long as possible
  • Keep baby away from sick individuals
  • Ensure clean hands when dealing with newborns
  • Use baby probiotics to ensure a healthy intestinal tract
  • Ensure the breastfeeding mom is eating a healthy diet
  • Ensure adequate exposure to sunlight or vitamin D

A baby’s immune system should be supported throughout the first phase of its life so that it can be encouraged to strengthen quickly. A healthy immune system is the foundation of a healthy childhood and later adulthood.

Lilian Presti is a registered holistic nutritionist who has worked in the nutrition and corporate wellness fields for more than a decade. She teaches pediatric nutrition and has been featured in Elle Magazine, Flare, Today’s Bride, The Weekly Scoop, City TV, and more. This article was originally published on