Possible causes of cerebral palsy during pregnancy or birth

Factors during pregnancy and at birth, often interrelated, may increase or contribute toward the chances that a baby is born with or will develop cerebral palsy (CP). Recent estimates suggest about 70% to 80% of children with CP experienced a disruption in normal brain development during fetal growth.¹ The exact cause of these disruptions is not known.

Birth trauma, in which a baby can be deprived of oxygen or sustain a brain injury, is a more rare cause of CP than previously thought, occurring in less than 10% of children with the condition. The exact cause-and-effect relationship between cerebral palsy and a difficult birth is often unknown. Sometimes a baby has an existing brain injury sustained during fetal growth that makes birth more difficult because of irregular postures or other problems. Often it is impossible to determine whether the brain injury or abnormality that results in CP occurred during fetal growth, a problematic birth, or a combination of factors.

There are several possible causes of CP during pregnancy or birth.

Genetic or chromosomal disorders

Babies born with certain genetic disorders, such as the blood-clotting disorder thrombophilia, have an increased risk of cerebral palsy. Babies born to teen mothers or to mothers older than age 35 have an increased risk for chromosomal irregularities that may result in CP.

Exposure of the mother to harmful substances during pregnancy

Examples of harmful substances include radiation or certain medications, such as thyroid hormone or estrogen. These and other substances may interfere with normal fetal development. A woman who drinks alcohol or uses illegal drugs during her pregnancy increases the chance that her baby will develop cerebral palsy.

Infections and health problems in the mother during pregnancy or birth

Infections such as German measles (rubella), cytomegalovirus infection (CMV), and toxoplasmosis in the mother, especially in the first 6 months of pregnancy, have been linked to the development of cerebral palsy. Chorioamnionitis, an infection that causes inflammation within the placenta, may also disrupt normal brain growth and cause CP.^{1, 2}

Certain infections (such as strep infections) of the uterus or the vagina may pass to the baby during delivery. If these infections reach the baby's brain, CP may develop.

Other health problems in the mother during pregnancy, such as bleeding in the mother's uterus, having large amounts of protein in the urine (proteinuria), or having high sugar levels in the mother's blood are all examples of other problems that may be linked to a fetus developing CP.

Having a prolonged or difficult birth

A baby who has a prolonged or difficult birth may be deprived of oxygen, nutrients, or blood for a long enough period to sustain brain injury. For example, delivery of the placenta (afterbirth) before the baby can result in a baby losing the blood or oxygen supply from the mother too soon, which can result in CP.

The American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) have established general guidelines to help health professionals identify whether a trauma incurred during birth is serious enough to cause brain injury that may result in a form of CP. These criteria include:³

• A blood sample, taken from the umbilical cord, that may indicate a baby was deprived of oxygen during birth.
• Moderate to severe swelling of the brain in babies born at 34 weeks or later.
• Other physical signs to indicate only spastic or dyskinetic types of CP are possible.
• Testing that has ruled out other conditions, such as trauma, blood clotting disorders, infections, or genetic disorders.

Citations

1. Wu YW, Colford JM (2000). Chorioamnionitis as a risk factor for cerebral palsy. JAMA, 284(11): 1417–1424.

2. Wu Y (2002). Systematic review of chorioamnionitis and cerebral palsy. Mental Retardation and Developmental Disabilities Research Reviews, 8: 25–29.

3. American College of Obstetricians and Gynecologists and the American Academy of Pediatrics (2004). Neonatal encephalopathy and cerebral palsy: Executive summary. Obstetrics and Gynecology, 103(4): 780–781.