When a fetus starts developing, its cells are not differentiated into organs. Instead, gradually, the organs are formed through different developmental stages. In total, five phases of fetal lung development take place before the lung is matured enough to help babies breathe after birth. These five phases occur in a stepwise process at a fixed gestational age. Read on the post to understand the stages of fetal lung development and the important aspects associated with each of them.
What Is Fetal Lung Development?
During the nascent stage of development, your little one is quite little indeed, no bigger than a ball of cells. Moreover, she has no special or dedicated cells yet. Fetal lung development begins at around four weeks of the gestational age. An early differentiation stage segregates cells into various different layers; one layer forms the organs. Lungs develop from the segregated cells and gradually become more efficient and adapt to respiration (1).
Fetal Lung Development Stages
Fetal lung development has five distinct phases, which we discuss below:
1. Embryonic Phase:
The embryonic phase of the fetal lung development begins at around four to five weeks of the gestational age. During the embryonic stage, two tiny buds branch off, one of the forms the right lung and the other forms the left lung. The larynx or voice box and trachea or windpipe develop from the foregut in an embryonic phase.
2. Pseudoglandular Phase:
The pseudoglandular phase of fetal lung development begins at around five to 17 weeks of gestational age. Medical studies conclude that the original lung buds branch into smaller and numerous units in the pseudoglandular phase. Over a time span, each bud develops into an independent respiratory unit consisting of a bronchiole and lots of capillary vessels that supply the blood to lungs for its oxygen requirements (2).
3. Canalicular Phase:
The canalicular phase of fetal lung development begins around 16 to 24 weeks of the gestational age. During the canalicular phase, a barrier develops between the air and blood, which enables oxygen to supply blood to respiratory capillaries and enable the carbon dioxide to depart from the respiratory capillaries in the lungs. Different tissue types develop in the fetus’ lungs during the canalicular phase distinguishing air-carrying tissues from the gas carrying tissues (3).
4. Saccular Phase:
The fetus gets in the saccular phase of the lung development at an around 26th week of gestational age (3). The production of surfactant starts in the saccular phase of lung development. Surfactant is nothing but a soapy fluid that helps keep the lung tissue delicate and prevents it from sticking within, tearing away during exhalation and damage when it compresses. Surfactant is extremely crucial during the delivery since it allows the amniotic fluid in the lungs to drain away and fills the lungs with air appropriately. Premature babies are more prone to respiratory issues and health conditions popular as lung collapse if they are born prior to the adequate formation of surfactant. Moreover, air sacs fill up during the saccular phase.
5. Alveolar Phase:
The alveolar phase, or the last phase, of fetal lung development, lasts until your little one sees the world and beyond until her early childhood. Additional production of surfactant starts during the alveolar phase. There is growth in the bronchioles and air sacs, or alveoli. Moreover, gas-carrying tissues of the lungs expand and become more efficient for carrying air during the alveolar phase. (4)
How To Know Fetal Lung Development For Safe Delivery?
The Fetal lung maturity or FLM test helps predict whether fetus’ lung development is appropriate for safe delivery. However, FLM prohibits delivery before 39 weeks. (1)
