Premature birth and low birth weight

Between 40% and 50% of all children who develop cerebral palsy (CP) are born prematurely.¹ In addition, the risk of a baby having CP increases as the birth weight decreases. A baby who is born prematurely usually has a low birth weight, less than 5.5lb, but full-term babies can also have low birth weights. Multiple-birth babies are more likely than single-birth babies to be born early or with a low birth weight.

Low-birth-weight, premature babies are more likely than full-term, normal-weight babies to have had developmental problems during fetal growth that can injure the brain. It is estimated that 70% to 80% of children with CP experienced a disruption in the normal development of parts of their brain during fetal growth.⁵ For example, a condition called periventricular leukomalacia, or PVL, which reflects injury to the white matter of the brain, is more likely in babies born prematurely than in those born at full term.

Risk factors before birth

A fetus's risk for developing a brain abnormality or injury that leads to CP increases when the mother has certain problems during her pregnancy, which may include:

• Infections, such as German measles (rubella), cytomegalovirus infection (CMV), and toxoplasmosis. When these infections occur during the first 6 months of pregnancy, the fetus is especially at risk.
• Infections in the mother's uterus or birth canal (vagina). These infections may cause inflammation in the placenta (chorioamnionitis), which can disrupt the normal growth of a fetus's brain and may contribute to getting periventricular leukomalacia (PVL).^{5, 6}
• Exposure to certain medications, such as thyroid hormones or estrogen.
• Use of alcohol, illegal drugs, and some prescription medicines (such as methotrexate).
• Other problems, such as bleeding in the uterus between the sixth to ninth month of pregnancy, large amounts of protein in the urine (proteinuria), or high blood sugar levels.

Risk factors for cerebral palsy at birth

Although rare, some babies develop CP as a result of complications during the mother's pregnancy or at birth. Risk factors include:

• Premature birth. Premature babies are at increased risk for developing bleeding in the brain (intraventricular hemorrhage, or IVH), which may result in CP.
• Difficult or prolonged labor. Brain infection or physical trauma (such as from the use of forceps or other instruments, which is rare) are all risks associated with a problem birth that can increase a baby's risk of developing CP. A lack of oxygen, although it occurs less commonly, also increases a baby's risk. But CP can itself cause a baby to have a difficult birth because of body movement and posture problems related to the condition.
• Placenta abruptio. The placenta usually separates from the wall of the uterus several minutes after the birth of the baby. If it separates before the baby is born, the baby loses the blood and oxygen supply from the mother, which increases the risk of developing CP.
• Infections in the mother's uterus or vagina, such as strep infections, that transfer to the baby during birth. Cerebral palsy can result if the infection reaches the baby's brain.

Risk factor after birth

Risk factors for developing CP just after birth or within the first 2 or 3 years of life are related to brain damage and include:

• A serious illness, such as severe jaundice, meningitis, or lead poisoning (very rare). Early signs of concern include breathing problems, low levels of thyroid hormone (thyroxine), seizures, and low blood sugar levels (hypoglycemia). Babies born prematurely or with a low birth weight are susceptible to these illnesses.
• Serious head injury from an accident or fall. This includes injury to a baby from shaking, throwing, or other force (shaken baby syndrome, also called intentional head injury or IHI).
• Lack of oxygen to brain tissues, such as the result of a brain tumor or a near-drowning incident.

Other risk factors

• Babies born to teen mothers or to mothers age 35 and older have a higher risk for cerebral palsy.
• Having a genetic or chromosomal problem, such as thrombophilia, a blood-clotting disorder, raises the risk for CP.