So a question that I often get asked, even by fathers, after a baby is born, is how a baby has gone from breathing the amniotic fluid of pregnancy to breathing room air, and how that process occurs. It's a very complicated process that initially involves blood vessels in a baby when a baby is in utero that we that we don't have as adults. But the simpler part of the process comes in the actual labor process. So when a baby is inside a mother's womb, there are extra blood vessels that keep the baby from needing lungs the way that we need lungs to process oxygen. So in the womb, the baby actually doesn't use its lungs almost at all, and so they're full of fluid. That fluid keeps pressure on the blood vessels of the baby's lungs so that they don't they don't open and they aren't needed.
When the baby is going through labor, the natural compressive forces on the baby in the pelvis, and with each contraction, actually push that fluid out of the lungs with every contraction. And overtime, what happens is as there's less and less fluid, the blood vessels in the lungs open gradually because there's less pressure on them. As that happens, they start to recognize more and more oxygen from the fetal blood supply, and they get even bigger. Over the entire labor process, as those vessels become larger and larger and start retaining more oxygen, one of the extra blood vessels that babies have starts to close, and that's one of the blood vessels that keeps the blood from going to the lungs while the baby is inside of the mother's womb. So as that blood vessel closes, and there's less pressure on those vessels in the lungs, the air starts to go preferentially to the lungs instead of just the circulation that the baby has already had.
When the baby is finally born, and the fetal head is delivered, the baby starts to take those breaths by response to the lack of oxygen that it's experiencing. And those initial breaths bring even more air into these blood vessels in the lungs that are opening, and allow those blood vessels to become as wide open as possible. Once those vessels are open, and that other vessel has closed, the baby will breathe exclusively through its lungs.
Sometimes what parents notice is that a baby is coughing or spitting after delivery, or has a difficult time transitioning to breathing, and that's often because the baby hasn't squeezed all of the fluid that was in its lungs while it was in utero out to breathe air. And that can cause babies to have what we call transient tachypnea of the newborn, which is retained fluid in the lungs, which leads to difficulty breathing, sometimes taking shallow short breaths instead of good deep breaths, and sometimes difficulty sleeping. So some of those babies will need to have extra care or extra suctioning to get some of that fluid out. You'll also notice that the nurses in the delivery room really want to make your baby scream, and that's because that screaming and crying helps bring even more oxygen into those developing lungs, and clear out the rest of that fluid.
