Labor & Delivery Causes
Labor & Delivery Causes
There are three broad categories of mechanisms for a brain injury to occur during or shortly after labor and delivery; Reduced Oxygen, Trauma, Reduced Glucose.
Two or more of these three can and sometimes do occur in the same delivery. That makes it difficult to sort out the primary event, that is, the mechanism that triggered the injury, because often the primary event will trigger other secondary responses that create or add to injury. For example, reduced oxygen to the brain ultimately results in reduced glucose levels, and that adds to the injury. Or trauma can compress blood vessels, thereby causing decreased oxygenation, and it is the decreased oxygenation which is the primary event—the actual mechanism of injury.
Only a careful review of the entire record by a trained physician or sometimes a team of physicians can find the real cause. Given today’s health care system, it is unfortunately rare for any treating physician to take the lead to really find out what happened and why the injury occurred.
To understand how reduced oxygen can cause brain injury
requires a little background. The baby gets its oxygen from the mother.
The placenta which implants into the mother’s uterus serves the same
function as a baby’s lungs will after birth. Oxygen in the mother’s
blood stream flows across the placenta and into the umbilical cord,
which has three blood vessels. Two thinner-walled veins carry oxygenated
blood from mother to baby, while one thicker-walled artery carries
carbon dioxide and waste products away from the baby by the mother’s
The mother’s oxygenated blood then supplies all the baby’s organs. Oxygen and nutrients, especially glucose, are essential for the proper growth, development and function of all the organs, including the brain. If the supply of oxygen is reduced or shut off brain damage occurs. Neurons die and the cell bodies break down. As that happens the contents of the neurons are released into the baby’s brain and it swells. The swelling can start the injury cycle again, by compressing blood vessels in the brain, which causes reduced blood flow in the brain, which further reduces the oxygen supply. If the swelling is severe and progresses it can lead not only to additional damage but ultimately death.
Anything that interferes with delivery of oxygen can start the cycle of injury. That includes any problems with the mother’s ability to supply oxygen to the placenta; any problem with the functioning of the placenta; damage to or compression of the umbilical cord, or internal circulation problems in the baby. Problems with the mother’s ability to adequately supply oxygenated blood (called profusion) to the placenta are rare, but can include low blood pressure (hypotension), high blood pressure (hypertension), preeclampsia, eclampsia, or maternal infection. When epidurals are used for pain management during labor the health care team needs to carefully monitor the mother’s blood pressure because epidurals can cause a dangerous drop.
The placenta is a remarkably efficient organ which generally has a great deal of excess capacity to handle problems which might develop naturally in the functioning of the placenta. The most common threat to this proper functioning is the impatience of the health care team taking care of the mother and baby during labor and delivery. Inappropriate use of Pitocin (a brand name for oxytocin, a hormone that stimulates contraction of the placenta) is dangerous and causes very serious impairments of the ability of the placenta to deliver oxygen to the baby. It is given to increase both the frequency and strength of contractions.
The placenta is embedded into the wall of the uterus. It consists of a pool of the mother’s blood vessels lying next to vessels on the baby’s side of the circulation across which oxygen and nutrients flow. When the uterus contracts, flow in or out of the placenta slows or stops. Imagine that your hand is the placenta. Your hand is open between contractions, “at rest” and oxygen flows freely. Ball your hand up into a tight fist—a contraction—and flow stops or is slowed. For the placenta to work properly there must be sufficient time between contractions for the placenta to recharge with a fresh supply of oxygen.
Excessive Pitocin can cause contractions to occur less than two minutes apart, thereby reducing the ability of the placenta to replenish its oxygen supply. Excessive frequency of contractions is called hyperstimulation of the uterus, or to be even more technical, tachysystole. Whatever the label the key point is that when contractions occur too frequently or are too strong someone on the health care team should stop the Pitocin. Failure to do so can lead to brain damage or death.
Impaired placental function resulting in brain injury can also
occur if there is a rupture of the uterus. That literally means that the
uterus tears. Ruptures of the uterus occur most commonly when a patient
who has previously had a caesarean section decides for some reason to
attempt vaginal delivery of a subsequent baby. This is known as a VBAC
(vaginal delivery after prior caesarean section). Historically, the rule
in obstetrics had always been “once a c-section, always a c-section.”
The rationale for that rule was that if the uterus did rupture the
placenta would stop functioning and the baby would suffer brain damage.
In the late 1980’s doctors encouraged women to try VBAC’s with horrible
results, primarily because they were unprepared to get the baby out
within fifteen minutes of the rupture and thus avoid some or all brain
The current rule is that a VBAC should only be attempted in settings where the obstetrician, anesthesiologist and surgery crew are all in the hospital and ready to get the baby out in a few minutes if any signs of a rupture are manifested. Many obstetricians have taken the position that the risk is simply too high to try a VBAC. The occurrence of uterine ruptures is also much higher if Pitocin is used in a VBAC setting.
The location of the placenta can also present a problem during labor and delivery. Normally the placenta is located on the side wall of the uterus. Occasionally it will implant at or across the opening of the uterus at the cervix. This is known as a placenta previa. Obviously if the placenta is located at the opening of the birth canal that precludes a vaginal delivery. Another problem is a placental abruption, which refers to a partial separation of all or a part of the placenta from the wall of the uterus. This process occurs naturally after delivery. If a pre-delivery abruption is small the placenta is usually large enough and has enough reserve that the baby will still get enough oxygen. Large abruptions are life threatening. They are manifested by a gush of blood out of the uterus and severe pain. Abruptions are emergencies that often require caesarean section.
Umbilical Cord Compression
As noted earlier compression of the umbilical cord can also lead to reduced oxygenation and brain damage. Some compression of the umbilical cord is normal as the uterus contracts. However, if a loop of umbilical cord comes out of the cervix in front of the baby’s head, it is called a cord prolapse. When the baby descends or contractions occur the cord is compressed significantly more than if the cord were normally placed. A prolapsed cord is an obstetrical emergency, which calls for a nurse or doctor to reach in and hold the baby’s head up and off the cord while the mother is rushed to the operating room for a c-section. The cord must be elevated until the baby is out. An occult cord prolapse is one where the cord lies low and is compressed during delivery but no one can feel or see the cord. This condition is diagnosed by seeing the signs of serious cord compression on the fetal heart monitor strips. The treatment for an occult umbilical cord prolapse is also an emergency caesarean section.
Trauma can also cause brain injuries, hypoxic injury and
cerebral palsy during labor and delivery. Trauma can be caused by a
number of forces being exerted on the baby. Sometimes these are forces
generated by the process of labor itself, and sometimes they are forces
caused by those attempting to deliver the baby. Inappropriate use of
vacuum extractors and forceps can cause brain damage through several
mechanisms. These include cerebral bleeds, cerebral contusions,
stretching and tearing of blood vessels and brain tissue, compression of
the brain with changes in blood flow and/or skull fractures. If used
appropriately and for the correct reason brain injury from forceps or
vacuum is not common.
Trauma causing brain injury can also occur from the cumulative effect of prolonged periods of contractions and pushing, forcing the baby’s head and brain repeatedly against the mother’s pelvis in a setting where the baby is a very tight fit for the particular pelvis. Pitocin is often used in that setting to attempt to force a baby that is actually too large out vaginally rather than proceed with a caesarean section. Trauma, forceps or vacuum extractors can also cause the formation of blood clots inside blood vessels, leading to strokes. If you are told your baby has had a stroke, you need to ask what caused the stroke and when the stroke occurred.
Long, difficult labors often result in a drop if the level of glucose (sugar) in the baby’s bloodstream. All babies should be checked after delivery to see if the glucose levels are appropriate. Excessively low glucose levels need to be corrected promptly, as failure to do so after can cause brain injury.