Spastic diplegia among children of low and normal birthweight.

Data from a population-based Cerebral Palsy Register in Western Australia were analysed for children born between 1956 and 1975, and low birthweight (LBW) and normal birthweight (NBW) infants were compared. Control populations of similar birthweight to the cases were available from Western Australia live births. The incidence of spastic diplegia among LBW infants was higher than among those of NBW. The relative risk for LBW infants increased from 12- to 26-fold between 1961 and 1975, and those who previously would have died were surviving to be more severely disabled, both physically and intellectually. For LBW infants the risk of spastic diplegia increased both with increasing maternal age and with birth order; for NBW infants birth order was of main importance. LBW singletons, NBW twins and those born in rural hospitals had increased risk of spastic diplegia. More antenatal problems were seen in the LBW group, whereas the NBW group had higher rates of perinatal problems. Thus the groups may differ aetiologically, the LBW group having a greater likelihood of being damaged in utero, whereas the NBW group may have become brain-damaged as a result of traumatic deliveries.