Friday, May 1, 2009
A few conversations recently have led me to believe that many attorneys who may be fairly new to obstetrics malpractice have misconceptions regarding the mechanism of hypoxia, fetal distress and brain injury in cases involving a nuchal cord where the umbilical cord is wrapped around the neck of the fetus prior to or during birth. The primary misconception is that the child is being strangled or suffocated by this cord around the neck. I’d like to address that issue today with an overview of the function of the umbilical cord and a discussion of how a nuchal cord can lead to hypoxia (a decrease in oxygen supply), brain damage and even death for the fetus.
First, we must understand that the fetus cannot breathe while in the womb. We all instinctively know this logically, but we’ve got to keep it in mind as we discuss the various aspects of this issue. Since the fetus cannot breathe within the womb, the mother has to deliver all the oxygen and clear away all of the carbon dioxide for the infant. This exchange is accomplished in the placenta. Oxygen from the mother’s blood is exchanged for carbon dioxide in the baby’s blood across the placental membrane. The umbilical cord contains the umbilical vein, that carries oxygenated blood from the placenta to the fetus, and the umbilical arteries, which carry deoxygenated blood from the fetus to the placenta. These vessels within the umbilical cord are essential for fetal gas exchange that takes the place of breathing while the fetus is inside the womb.
Now that we understand why the umbilical cord is so important, imagine if the umbilical cord vessels become kinked or blocked for some reason. In such cases oxygen, or an adequate amount of oxygen, can’t get to the fetus leading to fetal distress. Eventually, a prolonged reduction of oxygen will lead to the death of the cells and tissues of the fetus which is primarily evident in the brain since the brain is more sensitive and cannot readily repair itself. Luckily the umbilical cord is very tough and resilient, as any new father can testify if he’s been given those dull scissors and asked to cut it! The cord is hard to cut or tear, but it is possible to compress it or stretch it, and that is at the heart of the matter in nuchal cord cases.
It really doesn’t matter if the cord is wrapped around the neck, or the shoulder or the leg, the results can be the same. Everything may be fine throughout the entire pregnancy, but during delivery, as the fetus moves down into the birth canal, the cord can become stretched or compressed. These forces can block or slow blood flow through the umbilical vessels. The cord can also be compressed if it slips down between the head or shoulder of the fetus and the wall of the uterus where it is pinched in between. All of these problems are rare and unfortunate but natural processes. It is the task of the obstetrician to recognize the signs of fetal distress and act swiftly before the reduction in oxygenation causes permanent injury.