This is a follow-up of the Research Foundation Fact Sheet on risk factors distributed to UCPA Affiliates on January 7, 1994.

The Research Foundation has received a number of inquiries about a second publication on risk factors associated with cerebral palsy: Twinning and Cerebral Palsy: Experience in Four Northern California Counties, Births 1983 through 1985.¹

That publication makes the following points about twinning as a risk factor:

• Twinning is a significant risk factor for the occurrence of cerebral palsy as are prematurity, low birth weight, age of the mother, and being African American.
• A twin pregnancy resulted in a child with cerebral palsy 12x more often than did a singleton pregnancy.
• The increased risk was related to the tendency of twins to be low in birth weight (below 5.5 lbs.) However, a twin of normal birth weight also has a higher probability of cerebral palsy than does a singleton of normal birth weight.
• If one twin died before birth, the probability of the occurrence of cerebral palsy in the living twin is 100% greater than in a singleton live birth.
• If one twin died before birth, the probability of the occurrence of cerebral palsy in the living twin is 13x greater than if both twins lived.

COMMENT

No reason is known for cerebral palsy in a large percentage of cases. However, it appears to be true that the probability of cerebral palsy occurring is higher in twins than in singletons; this is particularly true if one twin dies before birth. The specific reasons why twinning is associated with the occurrence of cerebral palsy are unknown; several hypotheses are being studied to try to understand this association.

It is important to remember that more twins are born without cerebral palsy than with cerebral palsy; also, cerebral palsy occurs in singleton births. Thus, twinning is one of several risk factors, each of which are receiving targeted research attention. In twinning, scientists are focusing on in utero factors which place a twin at increased risk of cerebral palsy.

¹Grether, J.K. et al; Pediatrics, Vol. 92, #6, December, 1993