How Children’s Lungs Grow

The lungs are one of three major parts of the respiratory system and integral to your overall health and well-being. Your respiratory system is made up of the airway, lungs, and muscles for respiration. Lungs begin to form in the womb and continue throughout a child’s developmental years. Below you will find helpful information on how children’s lungs grow and how you can help them stay healthy.

How Children’s Lungs Grow

The stages of lung development are based on certain stages inside and outside the womb. Below you will find the stages of lung development in children.

First Trimester:

The first stage of lung development happens at just 5 weeks. A lung bud develops, splits into two, and eventually become the left and right lungs. At 12 weeks, the majority of the baby’s internal organs are in place, including the lungs. The baby’s lung buds will divide over and over again in branch-like shapes.

Second Trimester:

During the second trimester, the baby’s lungs have developed all of the main airways based off of the original lung buds. Air sacs and blood vessels begin to form as they will be needed once the baby is born. This is because they will get oxygen into the baby’s blood once they are born.

Third Trimester:

The last stage of development focuses on getting the lungs prepared for breathing once the baby is born. The smallest airways develop and the walls of the airways get thinner in order to help the baby breathe after birth. Surfactant is also produced at this stage as it is a necessary mixture of fats and proteins that help ensure the baby’s air sacs don’t collapse when they breathe out.


The baby is born with fluid in their lungs, but the hormones and pressure from the baby’s loud crying help remove the liquid so they can breathe air. When a baby takes its first breath, the lung’s blood vessels widen and blood flows to the lungs to get oxygen.

0-3 Years:

The first six months of a baby’s life results in a sharp increase in the number of air sacs in their lungs. After six months, the lungs continue to grow, but it is at a much slower pace than the first six months. By the time the child is 3 years old, their lungs are essentially a mini-version of adult lungs.

3-8 Years:

As the child grows, their lungs will also grow. The size varies from child to child.

Tips for Healthy Lungs

Healthy lungs are integral to one’s overall health due to the role of the respiratory system in everyday life. Below are some helpful ways to ensure your child’s lungs stay healthy.

  • Physical Activity: Help your child maintain a healthy and age-appropriate level of physical activity. Instilling this at a young age can help them maintain strong lungs and a healthy weight.
  • Avoid Smoking: You should avoid smoking during your pregnancy and also once your child is born. Second-hand smoke is unhealthy and can cause substantial harm to your child’s lungs.
  • Avoid Pollution: If possible, avoid polluted areas. If this is not possible, use a mask to reduce the impact of pollution on your child’s lungs.
  • Proactive Care: If you notice any issues with your child’s breathing or lung health, it’s important to talk with a medical provider as soon as possible.

Pediatric lung care in NYC is a great first step as they can provide you with a diagnosis and treatment plan that works for you. Letting issues with your child’s lung health go without medical intervention can cause more issues in the long run.

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If you are concerned about your child’s lung health, contact the top asthma doctor in NYC today for a consultation.

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