The Umbilical Cord

December 14, 2007

A developing baby is like a deep-sea diver in a way. Images of the lifeline hose of air pumped into the helmet of the diver going down is an appropriate metaphor for the umbilical cord of an unborn baby. Except that Man invented the hose, but God invented the umbilical cord, so it's just a bit more complicated. But the geometry of each can share the same perils. If flow is interrupted to either, the person at the other end, be it baby or diver, will be in great danger. Luckily for the baby, there are many safeguards.

First of all, the umbilical cord is long, usually around 55 centimeters. This offers a lot of slack so that a baby can move quite freely without danger. True, there is the chance of entanglement, but things are so loose that there is seldom constriction of the cord. Added to the safety is the volume of amniotic fluid, keeping the cord from being jammed up against the wall of the womb. In fact, some fetal distress during labor has been treated successfully with instilling fluid into the womb to restore the volume lost after the "water bag" has broken.

A cord wrapped around the neck happens often, but because of the reasons above is seldom a problem. If the cord is wrapped around two or more times, however--much rarer--there could be a noose-type effect, constricting one of the loops. This can usually be picked up while monitoring labor and steps taken for safe delivery.

The cord has a specialized membrane that plays a role in fluid exchange and other important interchanges. Contained within it are two arteries and a vein. These are the main channels for funnelling oxygen and nutrition to the baby. Protecting the blood vessels from being crushed by twisting or compression of the cord is a substance called Wharton's Jelly. It runs the course of the cord, surrounding the vessels, acting as a cushion to keep the vessels from kinking. Indeed, a baby whose cord has little Wharton's Jelly is at risk for fetal distress. Thankfully, this is usually an incidental finding after a normal delivery. Also, the regular pulsations within the cord, the constant forceful flow of blood, tend to act as a "straightening" phenomenon to prevent twisting.

True knots in the cord are very rare. Lifting arms above one's head doesn't cause this, as many patients have heard. This is a myth. In the cases of a knot, this is also something that is most often seen as an incidental finding after a safe delivery. Usually the knot is not tight, and the Wharton's Jelly does what it does best--protect the all-important vessels.

Cord entanglement among twins, however, is a real threat if they share the same sack. This type of twin pregnancy is usually the exception, most twins' cords being separated safely by a membrane between the two babies. But is important to use ultrasound as early as possible in the case of twins to demonstrate that the membrane is there.

Even with an obstetrician's knowledge of anatomy, it's still amazing to me that the cord is as safe a structure as it is. But the statistics are reassuring that near-foolproof safeguards provide the protection for this lifeline until we come up from the waters that we started in--until we come up for air.

Contemplating the Navel: Omphaloskepsis

Omphaloskepsis is a word you won't find in all dictionaries. It refers to the practice of meditating while contemplating one's navel. I would venture to say there aren't many omphaloskeptics in St. Tammany parish, unless of course there's some subculture I'm not aware of. What is it about the navel that intrigues us? Barbara Eden couldn't show hers. Belly dancers adorn theirs. Shirley McClain chains herself to out-of-body experiences from hers, or so she says. (Earth to Shirley, Earth to Shirley...) Bikinis expose them, rings pierce them, and lint collects in them. So why on Earth would I write about belly buttons in the first place? Is it because I ran out of every other conceivable medical subject there is to write about? Not to worry. There's an endless array of bumps, protuberances, pits, and orifices on the human body to keep me well stocked for years.

An immediate consideration for me in justifying today's subject is that doctors use them surgically to place their laparoscopes. Also, the exciting new research in using cord blood as a source of stem cells for cancer patients hints at a brave new world in transplants. But that's where my own omphaloskepsis would stop had I not had children who asked me about their own navels. A child's questions are extremely important on many levels, because besides simply requesting information, a child goes right for the heart of the matter. This often stimulates us to look at things in ways other than just the practical. Within every child's questions are inquiries into philosophies as well. A child seeks to get at the center of an issue. Not just What is a navel? but Why is there a navel?

We are a centrophilic species. Throughout history we have sought the centers of everything. The ancient geocentric scientists saw our world as the center of the universe. Then the heliocentrics correctly saw the sun as the center of our solar system, and many were persecuted for their theories. We are comfortable with centers. Even our two eyes, spaced well enough apart on our faces to give us true stereoscopic vision, align the two fields to create a central point for our gaze. We walk and run and somersault using our centers of gravity. And our center-seeking ways in some fashion emphasize the navel. Adam and Eve were missing two things we all have--Original Sin and belly buttons. The navel is nothing more than a scar, after all. But what was there before this skin scarred over makes our whole existence possible. Through this portal both life and nurturing flowed from our mothers. Two arteries and a vein exchanged nutrients and oxygen for us during the pregnancies that safely delivered us into the air-breathing world.

The cutting of the cord at birth is more than symbolic, for it challenges us to survive within our own machinery. The stump that remains withers, until we're left with what seems like the body's only joke--the belly button. The fascia is a tough fibrous tissue that is the main supporting layer of the abdomen. It's really the thing that holds our organs inside. The carnivores among us will encounter fascia as grizzle on steaks. A weakening of this layer is a hernia, which emphasizes its importance. During our development in the womb, there's a separation in the fascia at the navel, for the umbilical vessels need a way out and in while the umbilical cord's in operation. After birth when the navel remains, there is a small hole left which is technically a hernia as well. It is a point of weakness in our bellies we all are aware of. Whether we realize it or not. Of course, unless you're an omphaloskeptic, you probably haven't ever stopped to contemplate it.

(Wake up and smell the lint!)

Consider this: We're comfortable braving the elements of this world with these shells we occupy. We can throw our back to an onslaught, we can stiffen our abdominal muscles and invite your best shot, but just don't poke your finger in our navels as hard as you can. That would hurt bad. Somewhere, somehow, deep in the recesses of our brains lies a vague sense of physical vulnerability, and the navel is one of the places that is connected to that area. We are all able to close our eyes and with pin-point precision bring our index fingers straight to our navels. Why? The navel, the belly button, the umbilicus--all are words that describe a center of our physical bodies. An answer to my children about it involves the medical descriptions of how the arteries and vein in the umbilical cord flow this way and that, and then at birth when we become air breathing, lung-inflated beings, the flow alters, the portal there shutting down, the heart adjusting to a different type of circulation, and we're on our own. But this answer is incomplete, because we really do have a center. We were all connected to our mothers, and they to their mothers, and so on all the way back. We are all wired. We are all "on line," with our connections intact to the first people.

The lines drawn on paper that make up a family tree can easily be envisioned as cords of life, all inserting into navels down the page. The field of genealogy is learning the way to untangle and draw umbilical cords. Looked at that way, there's a certain beauty to a navel, whether it's an innee or an outee, as we are tethered snugly to our species. But I still don't know why Barbara Eden couldn't show hers.

 

Breech Presentation of a Baby--Head Over Heels Is Better Than Heels Over Head

 

Breech position means that the unborn baby is not head-first. The most common type of breech position is "frank" breech, in which the infant's buttocks are the first to descend into the birth canal. His or her legs are flexed at the hip, pointing the legs, straight at the knees, up toward the head. In contrast, a footling breech has the knee or knees flexed, such that the feet join the buttocks as the presenting part. This type of delivery can't be done vaginally--the laws of physics will not allow it to go smoothly. A frank breech, on the other hand, can deliver vaginally, the buttocks alone acting as an efficient dilating wedge much like the head would. But the statistics on delivering breech babies vaginally are a concern. Assuming of course the delivery was frank breech, the statistics say there is still an increase in the number of babies born who may suffer from "soft" neurological complications. This is even when everything seems to have gone well. Besides an increased risk of obvious trauma, soft neurological complications often go unnoticed but haunt parents later as hyperactivity, attention deficit disorder, dyslexia, and a host of other problems. The studies on the legitimacy of this theary have been at times inconclusive, prompting different experts to alternately advise vaginal versus Cesarean delivery for frank breech presentations.

Cesarean delivery is currently the most popular approach to seeking the best outcome for these babies. We must consider, however, the increased risks to the mother that come with cesarean section. It's true that the complication rate in private practice is low, but it's still higher than with vaginal delivery. So the answer seems to lie with talking these little babies into assuming a head-first presentation. That sort of diplomacy is called External Cephalic Version, a technique in which the baby is actually turned to the head-first position. We used to do this blindly at Charity Hospital, a forceful procedure involving two physicians, one pushing against the mother's abdomen, the other doing a pelvic exam to exert pressure there. This fell into disfavor because mothers really weren't crazy about the technique, and there seemed to be a feeling that there was probably a pretty good reason for the baby to be breech in the first place. Dr. Steve Fortunata, a perinatologist, espouses the newer thinking on the subject. The reason why version in the past failed often was that the patients who were scheduled for version weren't selected very well. Now, criteria such as how low the breech baby is and where the back is placed in the womb have made version safe and frequently successful. Ultrasonographic guidance and gentle manipulation, while a drug that relaxes the womb is used, have made the procedure desirable once again. Add to that the need to bring down C-section rates and suddenly it begins to make a lot of sense.

What has happened is that the old procedure using blind force against any breech baby has been replaced with a gentle maneuver done with a relaxed uterus under ultrasound in well-selected patients. It's called look before you leap, and it's an advance in that it's an improved rediscovery of an older procedure. It won't be the last time doctors fall head-over-heels for a safer outcome.

 

Q & A: No one knew I was breech until I was 6 cm dilated in active labor. Why was this a surprise if I kept all of my prenatal appointments?

 

Part of the problem with the whole delivery process is that it is considered a natural event, so obstetricians have to walk a fine line between letting things happen with no intervention versus too much intervention. Certainly insurance companies look at simple ultrasound as intervention and discourage its use as a routine diagnostic tool. Although obstetricians disagree with this type of thinking (we love ultrasound), still we are under scrutiny to order such tests only when there is overwhelming indication. Believe it or not, we are being tracked according to criteria such as complication rates, lab tests ordered, ultrasounds, etc. If a doctor were to fall out of the "norm" as defined by an insurance company's Utilization Review, that doctor may no longer be allowed to see those patients. Designed to manage costs for the consumer, which benefits you, it also tends to get good doctors fired sometimes.

I say all of this only to point out that it is easy to fall through the cracks while trying to practice good medicine on that fine line between not doing enough and doing too much. This is how a breech can be missed.

Also, it entirely possible, although less likely, that your baby was head first ("vertex") and flipped between the last appointment and your labor. Additionally, where the buttocks meet (the "buttcrack," if I may be so crude) can feel just like the loose joining of the skull bones, giving delivery personnel the mistaken impression that the baby is vertex until a wider access like 6 cm makes the truth more obvious.

These things would not happen if we did a jillion ultrasounds with each pregnancy, but these things do happen because we can't or are not allowed to do more than one or two ultrasounds (a lot less than a jillion). We doctors are "jillion-obstetricians" living in a "one or two" world.

An "oblique" position may be nothing more than a baby who hasn't dropped into the pelvis yet--what we called "engaged."

 

Incompetent Cervix, including Treatment: Mechanical Aspects of Premature Delivery

 

Premature delivery is one of the most expensive complications of human existence.  Besides the devastating emotional costs of physical suffering, there is the astronomical financial burdens put on families and society for the lifespans of babies affected.  There are many causes for premature delivery, but I'd like to ultimately expound on the incompetent cervix--a mechanical weakness of the mouth of the womb (cervix of the uterus) which diminishing its ability to hold in a pregnancy to term.

As a very cursory primer, however, let's get some other causes of premature delivery out of the way.  Infection inside the womb (amnionitis) can cause uterine irritability which can in turn cause contractions, usually a benefit to an unborn baby exposed to such an infection, but with the trade-off of premature delivery . Trauma like car accidents or falls can do the same, especially if there is injury to the placenta that provokes bleeding. The placenta itself is a common cause of premature delivery, with premature separation (called "abruptio placentae," or abruption) decreasing the amount of surface area responsible for oxygen exchange from mother to baby. Besides unknown causes, cigarette smoking or cocaine use can cause abruptions.

But premature delivery can be a result of disability to actually hold in the baby. The cervix is that circular, muscular, and fibrous opening which holds tight until contractions cause enough force to push the baby's head against it as a dilating wedge. When it finally gives way and opens, this is what is called real labor. But if there is a weakness in its structural integrity, it can fall open without the usual forces necessary. This is an incompetent cervix.

Actual labor at term is a complex mechanism that just happens to fall into place like so many tumblers in a lock. We are designed with a clock that ideally lines up the chemical and physiological tumblers only after a baby is mature enough to survive. But if the cervix is weak,  gravity alone may be enough to allow even a premature baby's weight to cause it to dilate. The gate is open, so to speak, and the baby can follow uninhibited into the outside world. The earlier before term this happens, the worse off for the baby of course.

In the 1950's an estrogen called DES was used to try to prevent miscarriage.  Not only did it not work, but it also caused congenital abnormalities in the developing female babies the mothers were carrying. These abnormalities were alterations in their daughters' reproductive tracts, ranging everywhere to weakening of the cervix all the way to cancer. Now in the late 90's, most of the children of these mothers have had their windows of risk come and go, so it's a moot point.  But the very problems which haunt a lot of today's handicapped generation are due to the weakening of the cervixes (cervices) of these women who came to childbearing age. With congenital weakening in these patients premature babies were born, many with the complications of prematurity that are at this time exacting a heavy price in money and heartache.

With the early diagnosis of precancerous lesions of the cervix, more and more young women and adolescents are having their cervices altered by freezing or burning away these lesions. Although this typically doesn't set one up for a weakened cervix, it can. Tragically, obstetricians often don't know there's a problem until a pregnancy so troubled forces a patient to undergo surgery to keep the cervix closed with or without continued bed rest.

The surgery is actually a simple matter of inserting a noose-like tape around the perimeter of the cervix to keep it closed until which time it can be snipped to allow delivery. Called a cerclage, it usually works well, but sometimes the compromise to the cervix is so profound that there's nothing left into which to sink the cerclage, thereby eliminating the benefit of this surgery. When this happens, prolonged bed rest, even in a hospital, may be necessary for months.

The usual cerclage placement is from a vaginal approach, but when there's nothing left of the cervix to work with, an abdominal approach is necessary to purse string that portion of the cervix that extends internally past the wall that is the back of the vagina.  Called an internal cerclage, it involves an abdominal incision and is best done before conception rather than after, because any surgery done during pregnancy, especially abdominal, is fraught with problem bleeding due to the extra blood vessel development that accompanies pregnancy.

That's the trick: to predict which patients won't do well with a second-trimester vaginal- approach cerclage before they even become pregnant, so that the internal one can be done before the pregnancy.

Internal cerclage has other problems.  Because it's placed via an abdominal operation, this mandates a C-section, because the vaginal birth route is closed off from within the abdomen. And although the cerclage can be left in for subsequent pregnancies, we're also talking about subsequent C-sections. Also, few ObGyn doctors have actually done them at all and are therefore uncomfortable with learning to do it on one of their patients.  Even in our practice, where we offer internal cerclage when clearly indicated, we've done less than ten in fifteen years. It's a simple operation, actually, but it is nevertheless...an operation.

Unlike the permanence of the internal cerclage, the vaginal cerclage is designed to be removed near the end of each pregnancy--a mere office procedure--allowing a vaginal delivery soon thereafter in the hospital.

So it's easy to see the pros and cons for each of these approaches. A vaginal approach is simpler and safer and can be removed to allow for a natural delivery later, but it is structurally more risky as success rates go. The internal cerclage is a better cerclage, but you're talking a surgery to put it in and a C-section for each baby thereafter. The perfect choice between the two does not exist--it's got to be a decision individualized for the patient.

Although it's somewhat barbaric to think of preventing premature delivery by "tying the sack" closed, still a cerclage is a lifesaver and an intuitively obvious solution to the problem of incompetent cervix.

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