What are the risk factors for a child developing cerebral palsy?
Just as there are particular types of brain damage that cause cerebral palsy, there are also certain medical conditions or events that can happen during pregnancy and delivery that will increase a baby’s risk of being born with cerebral palsy.
Research scientists have examined thousands of expectant mothers, followed them through childbirth, and monitored their children’s early neurological development to establish these risk factors. If a mother or her baby has any of these risk factors, it doesn’t mean that cerebral palsy is inevitable, but it does increase the chance for the kinds of brain damage that cause it.
Low birthweight and premature birth
The risk of cerebral palsy is higher among babies who weigh less than 5 ½ pounds at birth or are born less than 37 weeks into pregnancy. The risk increases as birthweight falls or weeks of gestation shorten. Intensive care for premature infants has improved dramatically over the course of the past 30 years. Babies born extremely early are surviving, but with medical problems that can put them at risk for cerebral palsy. Although normal- or heavier-weight babies are at relatively low individual risk for cerebral palsy, term or near-term babies still make up half of the infants born with the condition.
Twins, triplets, and other multiple births — even those born at term — are linked to an increased risk of cerebral palsy. The death of a baby’s twin or triplet further increases the risk.
Infections during pregnancy
Infectious diseases caused by viruses, such as toxoplasmosis, rubella (German measles), cytomegalovirus, and herpes, can infect the womb and placenta. Researchers currently think that maternal infection leads to elevated levels of immune system cells called cytokines that circulate in the brain and blood of the fetus. Cytokines respond to infection by triggering inflammation. Inflammation may then go on to cause central nervous system damage in an unborn baby. Maternal fever during pregnancy or delivery can also set off this kind of inflammatory response.
Blood type incompatibility
Rh incompatibility is a condition that develops when a mother’s Rh blood type (either positive or negative) is different from the blood type of her baby. Because blood cells from the baby and mother mix during pregnancy, if a mother is negative and her baby positive, for example, the mother’s system won’t tolerate the presence of Rh-positive red blood cells. Her body will begin to make antibodies that will attack and kill her baby’s blood cells. Rh incompatibility is routinely tested for and treated in the United States , but conditions in other countries continue to keep blood type incompatibility a risk factor for cerebral palsy.
Exposure to toxic substances
Mothers who have been exposed to toxic substances during pregnancy, such as methyl mercury, are at a heightened risk of having a baby with cerebral palsy.
Mothers with thyroid abnormalities, mental retardation, or seizures
Mothers with any of these conditions are slightly more likely to have a child with cerebral palsy.
There are also medical conditions during labor and delivery, and immediately after delivery, that act as warning signs for an increased risk of cerebral palsy. Knowing these warning signs helps doctors keep a close eye on children who face a higher risk. However, parents shouldn’t become too alarmed if their baby has one or more of these conditions at birth. Most of these children will not develop cerebral palsy. Warning signs include:
Babies with cerebral palsy are more likely to be in a breech position (feet first) instead of head first at the beginning of labor.
Complicated labor and delivery
A baby who has vascular or respiratory problems during labor and delivery may already have suffered brain damage or abnormalities.
Small for gestational age
Babies born smaller than normal for their gestational age are at risk for cerebral palsy because of factors that kept them from growing naturally in the womb.
Low Apgar score
The Apgar score is a numbered rating that reflects a newborn’s condition. To determine an Apgar score, doctors periodically check a baby’s heart rate, breathing, muscle tone, reflexes, and skin color during the first minutes after birth. They then assign points; the higher the score, the more normal a baby’s condition. A low score at 10-20 minutes after delivery is often considered an important sign of potential problems such as cerebral palsy.
More than 50 percent of newborns develop jaundice after birth when bilirubin, a substance normally found in bile, builds up faster than their livers can break it down and pass it from the body. Severe, untreated jaundice can cause a neurological condition known as kernicterus, which kills brain cells and can cause deafness and cerebral palsy.
An infant who has seizures faces a higher risk of being diagnosed later in childhood with cerebral palsy.