Genetic factors in cerebral palsy play a role as part of a multicausal pathway and as a sole source of damage.  Maternal mental retardation, motor deficit in an older sibling, maternal seizures, and more than two prior fetal deaths were all associated with cerebral palsy.  Genetic origins of cerebral palsy can surface in cultures where marriage among people related by birth or ancestry is common.  The same result occurs in locations that are small, isolated areas.  A 1991 study found such an effect among the Amish of North America. 

Studies report that in families where cerebral palsy has occurred, the chance of it happening again is higher when compared with controls.  When twins are involved, if one of the twins dies in the womb or after birth, the chance that the second twin will contract cerebral palsy increases whether they are identical twins or not.  Yet it has been estimated that if the twins are the same sex and share one placenta, the chance that both twins will suffer cerebral palsy increases.

Hart, Hilary M., ed.  Clinics in Developmental Medicine.  London:  Mac Keith Press.   Alberman, Eva; Blair, Eve; and Stanley, Fiona.  Cerebral Palsies: Epidemiology and Causal Pathways.  London:  Cambridge University Press, 2000.  (The book is part of a series of hardcover monographs published by Mac Keith Press.  Four new ones are published each year.  The distributor is Cambridge University Press.)