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Pregnancy weekly

5 Phases of Fetal Lung Development

A baby growing inside your womb is miraculous, and it is indeed quite astonishing to see how a small group of cells transforms into a beautiful baby. However, the process of formation of various organs is very intricate and begins as soon as you conceive. One of the most important developments that help your baby sustain outside the mother’s womb is the development of lungs. Browse through the following article to know how fetal lung development takes place and more.

What is Foetal Lung Development?

If you are wondering when a fetus’ lungs start to develop, well, your baby’s lungs begin to develop at around four weeks of gestational age – that is around the embryonic phase. In the initial stages of development, your baby may only have some undifferentiated cells. However, as time passes, these undifferentiated cells start separating into unique layers, and thus, fetal lungs begin to develop.

What Are the Fetal Lung Development Stages?

Fetal lung development can broadly be classified into five stages. We shall be discussing all these stages briefly in the following paragraphs:

1. Embryonic Phase

This phase begins around the fourth to the fifth week of gestational age. In this stage, there are two buds that branch off. One of it helps in the formation of the right part of the lung; the other helps in forming the left part. Also, during this phase only, the voice box (larynx) and windpipe (trachea) start developing from the foregut.

baby in belly

2. Pseudo Glandular Phase

This phase begins somewhere around the sixth week and extends up to the sixteenth week. During this phase, the lung buds further branch out into several tiny units to grow into an independent respiratory unit. This includes various capillary vessels and bronchiole, which transport blood to the lungs for oxygen.

3. Canalicular Phase

This phase begins around the 17th week and lasts until the 25th week of gestation. The main development that happens during this phase involves developing an important barrier within the lungs. This barrier aids oxygen to supply blood to respiratory capillaries, and it also facilitates carbon dioxide to escape from the respiratory capillaries. As time passes, it may be easy to distinguish between gas-carrying tissues and air-carrying tissues.

4. Saccular Phase

This phase begins at around 25th week to 36th week of pregnancy. The formation of surfactant begins, which is a soapy fluid that keeps lung tissues from sticking to each other, tearing away during the process of exhalation, or damaging themselves in case of compression. Babies who are born with the inadequate formation of surfactant may develop respiratory issues and other breathing problems.

5. Alveolar Phase

This marks the last phase of fetal lung development and this phase begins before the birth and continues until early childhood. In this stage, more surfactant and alveoli (air sacs) are formed, which helps the tissues to carry the gas to the lungs. This helps in making the lungs more proficient in the movement of more air, as the baby grows.

Factors That Affect An Unborn Baby’s Lung Development

There are factors that may affect the development of the lungs of your unborn baby, and some of the reasons are as follows:

  • It is also observed that male babies are more prone to lung developmental issues in comparison to female babies.
  • The ethnicity of the parents also plays a role. Thus, South East Asian and black babies are more at risk of having lung developmental issues.
  • If a mommy-to-be smokes during pregnancy, it will adversely affect her fetus.

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