Take my breath away

I had dinner with Danielle last week and, as is the way nowadays, a good proportion of the conversation was dedicated to all things baby.

Danielle knocked it out of the park on the asking a pregnancy question that hasn’t been asked before with the conundrum of what do babies use their lungs for before they are born? To what extent do they breathe?

So the easy bit is that the baby will get the oxygen it needs direct from the mother lung via the umbilical cord and the placenta direct to its bloodstream and hence to the heart. The umbilical cord will then ultimately take the carbon dioxide away.

The crazy thing is that usually the lungs are critical to the oxygen / carbon dioxide exchange, but for a fetus the lungs are redundant. Enter the foramen ovale. Never heard of it? Neither had we! As LiveStrong explains, apparently it is a valve in the fetal heart that allows oxygenated blood to pass directly from the right atrium to the left and hence out to the rest of the body bypassing the lungs.
20130527-225626.jpg

(For those interested in bizarre fetal blood features, see also ductus arteriosus which is another shunt which diverts the majority of blood from the lungs, and the ductus venosus which allows oxygenated blood to bypass the liver).

So what are the lungs up to?

Well they are developing away, producing more and more air sacs. And they get some practice because from the 10th week of development, the fetus will start breathing and swallowing amniotic fluid. So up until birth, the baby’s lungs are full of amniotic fluid which includes surfactant, a soap-like substance which keeps the air sacs open. Practicing breathing in amniotic fluid will also help the fetus develop the muscles in his chest so it can make that critical first proper breath once out in the big wide world.

So what about after birth?

LiveStrong explains it all:
“During birth, several processes occur simultaneously – all of which end with the newborn breathing through his lungs. The blood vessels in the umbilical cord constrict, cutting off flow from the placenta. Newborn blood oxygen levels drop rapidly, and carbon dioxide levels rise. The newborn’s chest, constricted from the birth canal, expands – causing the lungs to expand. The expansion of the lungs causes the newborn to draw in a breath, which also causes the forum ovale to close. When the forum ovale closes, blood flows to the lungs to pick up oxygen and the lungs fill to capacity with air.”

The miracle of breath!

Leave a Reply

Your email address will not be published. Required fields are marked *