Cerebral palsy is a term used to describe a chronic condition affecting body and/or limb movement and the control of muscle tone and coordination. It is caused by damage to one or more specific areas of the brain during periods of brain development; there is usually no damage to the sensory or motor nerves controlling the muscles. The brain damage is not progressive; however, the characteristics of disabilities resulting from brain damage often change over time. 
In examining the contributing factors that influence the occurrence of cerebral palsy and the specific causes of cerebral palsy, five (5) time periods need to be considered: 

1. Preconception (parental background) [1] 
2. First trimester of pregnancy (0 to 3 months) [2] 
3. Second trimester of pregnancy (3+ to 6 months) [3] 
4. Third trimester of pregnancy (6+ to 9 months) [4] 
5. Perinatal period and infancy (first 2 years post natal) [5]

At a "critical time," either a single factor or a combination of factors can contribute to or can cause damage to the developing brain. All factors have not yet been identified. However, a large number are known, and their most influential times of occurrence are being identified. 
These factors and the times when they are most likely to have an impact on the developing brain, are listed below. 

1. Preconception (Parental Background)
   Biological aging (parent or parents over age 35)
   Biological immaturity (very young parent or parents)
   Environmental toxins
   Genetic background and genetic disorders
   Malnutrition
   Metabolic disorders
   Radiation damage
2. First Trimester of Pregnancy (0 to 3 months)
   Early: 
   Endocrine: thyroid function; progesterone insufficiency
   Nutrition: malnutrition; vitamin deficiencies; amino acid intolerance
   Toxins: alcohol; drugs; poisons; smoking

   Late: 

   Endocrine: thyroid function; progesterone insufficiency
   Maternal disease: thyrotoxicosis; genetic disorders
   Nutrition: malnutrition; amino acid intolerance

    

3. Second Trimester of Pregnancy (3+ to 6 months)
   Early: 
   Infection: CM virus; rubella; toxoplasma; HIV; syphilis; chicken pox; subclinical uterine infection

   Late: 

   Placental pathology: vascular occlusion; fetal malnutrition; chronic hypoxia; growth factor deficiencies
4. Third Trimester of Pregnancy (6+ to 9 months)
   Early: 
   Prematurity and low birth weight
   Blood factors: Rh incompatibility; jaundice
   Cytokines: neurological tissue destruction
   Inflamation and infection: chorioamnionitis

   Late: 

   Prematurity and low birth weight
   Hypoxia: placental insufficiency; perinatal hypoxia
   Infection: listeria; meningitis; streptococcus group B; septicemia; chorioamnionitis
5. Perinatal Period and Infancy (first 2 years post natal)
   Endocrine: hypoglycemia; hypothyroidism
   Hypoxia: perinatal hypoxia; respiratory distress syndrome
   Infection: meningitis; encephalitis
   Multiple births: death of a twin or triplet
   Stroke: hemorrhagic or embolic stroke
   Trauma: abuse; accidents

© UCP Research & Educational Foundation, September 1995

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