Clamping Umbilical Cords

Umbilical cords…most people know very little about them.  They probably know that they used to have one…and probably know that it made their belly button.  They may know that it was once attached to a placenta…but beyond that, most people can’t understand why I admire umbilical cords.

Let me try and explain it to you.

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One of my most popular blog posts is this one on umbilical cords…

Magic Umbilical Cords

In case you haven’t seen it yet – it is one of my shortest blog posts, yet has become one of my most shared and well known. I have had an interest in the umbilical cord and our rush to clamp it for a while, and had previously looked for pictures to demonstrate the changes that the cord goes through from immediately after birth until it is no longer functional. Imagine my surprise when I couldn’t find the desired pictures even when looking through google images!! Billions of images shared, but that one eluded me. So one morning I watched a friend (whom I had watched birth her first baby) push her second baby out into the world – and was struck by the beauty of this thick, blue, pulsing umbilical cord. I asked the mother if I could take pictures of the cord to use for educational purposes, and she said yes. I asked my student if she could grab the camera and take some pictures for me…and she took those amazing pictures that I was then given permission to share in the hopes of educating others as to the importance of respecting the function of the cord.

(sidenote – lesson learned…next time I will watermark the images after editing them)

I knew that I loved the pictures and have a respect for the umbilical cord, but I guess I didn’t realize how popular that blog post would become or I would have seized the opportunity to educate more on the wonders of this cord that connects baby to mother. Here are some really interesting facts that you may or may not know about the umbilical cord.


The debate is far from over – should we clamp the umbilical cord immediately at birth, or should we wait until it has stopped pulsing or the placenta is delivered?  Those advocating that we delay cord clamping often say that doing so would allow oxygen to continue to be delivered to the baby until baby begins breathing – but the truth is that it does even more than deliver oxygen, it delivers blood.  At first glance that might seem like the same thing – but perfusion of blood can be more important in the immediate protection of brain function than oxygen levels.


What causes brain damage in a person? If I asked that question to a classroom of students most of their hands would go up and I would easily get the correct answer of “Lack of oxygen!” That is correct. In a person, lack of oxygen (otherwise known as hypoxia) eventually causes brain damage. Usually the cause of the hypoxia is respiratory depression or heart failure. In other words…. the reason that they would be without oxygen long enough to cause brain damage is that they have stopped breathing or their heart stopped pumping the blood.

What would cause a neonate (newly born baby) to be hypoxic? It’s not the lungs or the heart that had a problem – it’s the cord. The solution is to protect the return of the function of the cord, thus correcting the problem. If the cord was the problem, then the cord is the solution.

Here is something that not everyone understands – perfusion of blood to the brain has more immediate repercussions to its function than oxygen level of that blood. Babies in utero grow and thrive in an oxygen level much lower than ours. Oxygenated blood comes through the umbilical cord, mixes in the inferior vena cava and in the heart with DE-OXYGENATED blood from the inferior+superior vena cava….and that mixed, lower oxygenated blood is then circulated throughout the baby.  Even with lower oxygen levels, they thrive.  Their skin is purple, but their system is perfused with blood that is lower in oxygen than ours. This offers protection from hypoxic injury…as long as organ and placental perfusion are good.

Adult brains and organs aren’t much different….an adult can survive without oxygen of any sort (ie. breathing pure nitrogen) for 5 minutes and, while they will lose consciousness, will suffer no long-term effects. No brain damage. However, if you occlude the cerebral artery (stop blood flow to the brain), brain damage begins almost instantly. Losing perfusion of the blood to the brain is much more damaging to the tissue than losing the oxygen to the brain.

It is understandable, then, that our primary goal for the depressed neonate should be allowing the placenta and cord to re-perfuse the baby and his/her organs immediately after birth!  If baby’s system has been compromised of blood supply, then it is imperative that we do not remove that cord until perfusion has been re-established.  Providing that baby with oxygen via a mask with positive-pressure-ventilation to resuscitate doesn’t address the PROBLEM – which is the perfusion of blood to the baby’s system at the moment of birth.


A fully functioning cord…this baby was born at home. His mother is snuggling this baby, oblivious of the gifts this cord is providing her baby.


The same baby baby, now snuggled with his daddy…while still attached to the placenta that is in the bowl. Notice that his cord, previously thick and purple, is now thin and opaque white.



Perfusion of the liver helps the baby maintain glucose levels as the baby now needs to tap into their own glycogen stores in the liver to maintain glucose levels. The liver is also responsible for processing bilirubin and preventing jaundice. While it is understandable that one could think that having a higher blood volume at birth could contribute to physiological jaundice of the newborn, having a liver that is properly perfused could actually assist in preventing jaundice.
Perfusion to the kidneys is necessary to maintain blood pressure which is required for fluid, electrolyte, and acid-base regulation after birth.
Perfusion of the lungs “erects” the alveoli and initiated respiration – with perfusion resulting in lung aeration before respiratory efforts even start. Respiration is a reflex controlled through the central nervous system which needs copious perfusion of the reflex circuit and well as the respiratory muscles for it to function. A large portion of the blood volume given by the unclamped cord at birth goes towards establishing the pulmonary (lung) blood flow.

This is usually where I take a moment to reflect in the awesomeness that happens in that moment of birth…when the cord is blue and pulsing, when baby is changing from purple to pink – when this cord, that has supported this baby their entire life, gives its final gift before it will collapse, almost as if it has given its life for this baby.


The moment of birth is dramatic…for no one more than for the baby. The umbilical cord works to make this sensitive time easier by protecting the baby on many levels.

First, it protects their temperature.  Until the cord stops functioning, it is pumping mother-heated blood from inside her body (the placenta) through the cord into the baby – thus acting like a circulating heater keeping baby’s temperature stable until baby can be snuggled into mother’s warm arms.  I’ve seen nurses, doctors, and midwives rush immediately to rub baby with towels, drying baby off, slipping a hat on their head…all in an effort to maintain baby’s body temperature.  The truth is that for the minutes that the cord is functional, there is really no reason for any of that yet.  Once in mother’s arms, her body heat will adjust to maintain the baby’s body temperature perfectly.

clampsSecond, it gives the baby a grace period by providing oxygen (along with blood, see above), giving the baby time to initiate respiratory efforts.  I’ve heard medical care providers say that a depressed newborn (one with low APGAR scores – or one who isn’t breathing and responsive immediately) is one of the instances in which delayed cord clamping can not be accomplished as the baby needs medical attention in a warmer where the neonatal team has full access to that baby. Proponents of delayed cord clamping state that a depressed newborn is when it is most crucial that we don’t clamp that umbilical cord in order to support the baby until respiration is established.

The truth is that in 1957 (over 50 years ago!) a paper published in the Lancet demonstrated just how dramatic the support and protection of the cord can be for a baby. In the report, the medical team tracked the weight of a newborn who was wrapped immediately at birth in warm cloth and placed on a scale near mother’s vagina. Baby didn’t start breathing for 10 full minutes. For 10 minutes they watched the baby and recorded it kicking the bed (at 4 minutes), recorded the baby’s weight as it changed with uterine contractions that pushed blood into the baby….and finally recorded the baby’s weight surge immediately after the baby began breathing (as a full 100ml [.42 cup] of blood was pushed into baby from the placenta), finally stabilizing after the cord stopped functioning. The baby was never in any danger even though it took 10 minutes to establish respiration.


Initially at birth, the placenta and umbilical cord continue to function similarly to how they did in utero. After birth as it is exposed to temperature change, the gelatinous substance in the cord (Wharton’s Jelly) that was firm and thick and protected the integrity of the two arteries and single vein inside the cord….begins to chemically change, liquefying, collapsing the cord and restricting the vessels it contains. As the Wharton’s jelly begins to collapse, it first restricts the smaller arteries (that bring blood from baby to the placenta) before finally collapsing the larger umbilical vein (that brings blood from the placenta to the baby. Clamping the cord prematurely interrupts this process and demands immediate respiration from the newborn as well as possible severe repercussions if that doesn’t occur.


In the Gunther study mentioned above, they found a 100ml surge within one minute of the baby beginning to breathe. That may not seem like much until you think of it this way…

* the estimated blood volume of a baby is determined as 85ml for every kilogram of full term baby.
* the average baby weighs approximately 7.5 pounds. Converting that to kilograms is approximately 3.5 kg (approximating for simplicity)
* using these calculations – the average blood volume of a newborn baby is approximately 297.5 ml.


A fully functional umbilical cord being clamped by the physician immediately at birth. Baby was then immediately taken over to a warmer, rubbed down, and kept for almost half an hour.

While they did not mention the size of the newborn studied….if it was an average sized baby, he or she would have received approximately 1/3 their total blood volume FOLLOWING the initiation of respiration. Studies have shown that it can be even more significant – up to 50%. If you or I lost 30-50% of our blood volume, we would be in stage 3 or 4 (out of 4) hypovolemic (low blood volume) shock. We usually are symptomatic and in the beginning stages of hypovolemic shock at only 15% blood loss. A loss of 50% usually requires severe intervention to prevent death.



The more I learn of the umbilical cord and its function, the more I am in awe at its incredible abilities to protect our babies both inside and out of the womb. I have yet to see ANY compelling arguments that would convince me that we should do anything in that immediate postpartum period that would interrupt the function of the cord – especially if baby is compromised. In fact, I believe strongly that to do so is to put that baby at significant risk – and as health care practitioners, how can we justify that? The only logical approach is to leave the cord alone until the placenta has delivered, only clamping before then in extreme circumstances and after exhausting all other options.