Since so much depends on that life line called the umbilical cord, it’s a wonder it isn’t predominate among our worries in obstetrics. But there are many safeguards that protect this structure.
First of all it’s long enough to not get yanked with undue traction. Second of all, the blood vessels within it, two arteries and a vein, are cushioned by a gel called Wharton’s Jelly, which can keep these vessels from getting crimped even when there’s a knot in the cord. True knots in the cord are unusual, but most end up causing no problems because of Wharton’s Jelly. There are exceptions, and these exceptions are real tragedies, because when the umbilical cord stops providing oxygen and exchange of nutrients, the baby will die.
“Too tight” a cord is probably just an expression simplifying what happened to that baby. If it was too short, which is rare, the biggest complication is placental abruption, in which any movement of the baby can yank on the cord’s insertion point on the placenta, causing the placenta to pull away, leading to hemorrhage. Also, when the baby went through delivery, a too short cord could put such tension on the blood vessels within it that it would be compromised, showing up on a monitor as fetal distress.
More than likely the cord was wrapped around the baby’s neck several times. Wrapped around once is actually quite common (20%) and only shows as a transient mild distress on the monitor moments from delivery. It is called a “nuchal cord,” and can cause some real distress when it wraps around twice or more and the length of the cord is short enough to cause undue tension. I once had a patient laboring fine until the heart tones crashed. On doing an emergency C-section, the baby had a nuchal cord times four (that is, wrapped around the baby’s neck four times). In residency, I once knew of a patient who had a nuchal cord times seven! But this was probably because this baby had an abnormally long umbilical cord.
Ultrasound can sometimes see a nuchal cord. There are doctors who have researched nuchal cords and have advocated pre-emptive C-sections to prevent just the thing you’re asking about, but this hasn’t been proven to affect the outcome in the general population all that much. And in today’s managed care climate, where everything is being done to bring down the C-section rate, these admonitions for C-section don’t go very far.
Sometimes there is a stillbirth for absolutely no discernable reason, but further investigation will reveal a Listeria infection or subtle genetic abnormality. Sometimes there will be no reason, and this can be so frustrating that a doctor will use his or her best guess, looking at the cord as the most likely culprit—but it is a guess—a good guess, but a guess.
Don’t let this rare but tragic event discourage you in how you think about pregnancy. In most cases everything is fine. In the rest, many of them have problems that can be addressed. And only the very few have problems so severe that the intensity of the outcome overwhelms all of the good outcomes because of notoriety.