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Not a question you have ever thought about, me neither. But apparently, it is a commonly asked question: Does a baby fetus have gills in the womb?
I know you are thinking that this is a joke, right?
But when you think about how babies are completely submerged in the amniotic fluid until the day they are born. It started me wondering how do they breathe?
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Do Babies Have Gills In The Womb?
Babies do not have gills when they are in the womb. At least not in the traditional sense.
For many many years, textbooks stated that early embryos have tiny pouches that reflect an earlier fish stage. However, this has been proven completely false and is just another great evolutionary myth.
But in their very early stage of development, they do have features such as gill arches which are shared with other animals like fish. These never develop into gills and babies do not breathe underwater while in amniotic fluid.
Let’s take a look at what pharyngeal gill arches are!
What Are Pharyngael Gill Arches or Gill Slits In A Baby Fetus?
To really understand where this myth comes from we need to discuss the first few things that happen after a baby is conceived.
Fertilization is when the sperm penetrates the egg causing it to begin dividing into new cells.
Implantation, The ball of cells, called a blastocyst, attaches to the uterus, where it will begin to grow into a baby.
Embryo Formation, Around the 4-week mark, the egg has transformed into an embryo around the size of a poppy seed.
All vertebrates, any animal with a spine, such as mammals, birds, reptiles, amphibians, and fish. They are all very similar in development.
All vertebrates form something called pharyngeal arches, or pharyngeal gill slits in their throat region very early in their development.
Around the time that your baby becomes an embryo is when the first of 5 pharyngeal arches begin to develop. In fish, these go on to become their functioning gills. But in humans, they develop into the foundation for the bones of our jaw and ears.
Ok so babies don’t have gills, but how do they breathe in the womb?
How Do Babies Breathe In The Womb?
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Developing babies need oxygen very early in the pregnancy. But babies do not take their first breath until they are born.
This means that babies really don’t breathe in the womb. They receive all the oxygen that they need from their umbilical cord and it does this until they take their first breath when they are born.
Your baby’s lungs are not completely developed until the third trimester.
Between 24-36 weeks of pregnancy, is when the lungs start to develop alveoli, these are the tiny sacs that fill with oxygen. But until these sacs are fully developed, a baby may have difficulty breathing outside of the womb.
This is why when babies are born prematurely they often have issues with breathing as their lungs are not fully developed.
How Do Babies Learn To Breathe?
From around 32 weeks your baby’s lungs are usually developed enough to breathe oxygen.
So over the next few weeks, they begin to practice their breathing by carrying out small swallowing movements while expanding and contracting their lungs.
By 36 weeks, their lungs are not only fully formed but are also now well-practiced. They are considered as almost full-term by this time.
After The Waters Break
This will be your baby’s first experience with oxygen, but while they are still connected to their umbilical cord they don’t need to worry about it. As that cord is still providing them with everything that they need to survive.
During labor, contractions actually squeeze your baby and help to eliminate the amniotic fluid from their lungs.
This gets them ready to take their first breath. And once their umbilical cord is cut they are ready to take their first big solo breath!
The Final Thought
So a quick recap. Babies definitely do not have gills and in fact do not breathe in the womb, well not in a conventional way.
Babies’ lungs are not fully developed until they are around 32-36 weeks old, by this time they have been practicing their breathing technique and have it down to a fine art.
In the meantime, they receive all that they need from oxygen to nutrition through their amazing umbilical cord and placenta.
This actually means that mom is doing all the hard work for them and this continues until they are born and they take their first solo breath!