There are a number of other variables or risk factors associated with the development of cerebral palsy.  They include infant thyroid hormone levels, coagulation disorders or clotting defects in the mother or infant, vaginal bleeding, hypocalcemia (low calcium concentration), polycythemia (increase in hemoglobin content), infant hypoglycemia (lower than normal level of glucose in the blood), the mother being exposed to radiation or methyl mercury, and delivery room depression.

Infants weighing 3.3 pounds whose mothers exhibited vaginal bleeding at the time of admission were significantly more likely to develop cerebral palsy if they were more than 29 weeks into gestation.  Premature babies may have lower than normal levels of the thyroid hormone thyroxine.  This condition, called hypothyroxinemia, may be a sign of cerebral palsy, a cause, or both.  In Britain, it has been reported that premature infants with hypoglycemia were increasingly likely to acquire cerebral palsy as their blood sugar decreased.

If a mother is undergoing radiotherapy, cerebral palsy may be engendered by the intervention.  Radon exposure in other contexts can have the same result.  There have been several cases where localized environmental damage (for example, methyl mercury poisoning) has resulted in fetal contamination and contraction of cerebral palsy.

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.)

Stanton, Marion.  The Cerebral Palsy Handbook:  A Practical Guide for Parents and Carers.  London:  Vermillion, 2002.