To investigate the etiology of spastic diplegia (SD) of prematurity, we compared 
the prenatal, perinatal, and neonatal course of 18 preterm infants with SD to 
that of a control group of preterm infants without SD. No significant 
differences between the group with SD and the control group were found in most 
of the perinatal and neonatal factors analyzed. Significant differences were 
found in birth weight, birth head circumference, and the one-minute Apgar score. 
Controlling for gestational age, infants with SD weighed less at birth, had 
smaller heads, and were more often briefly neurologically depressed. 
Intracranial hemorrhage and neonatal seizures occurred significantly more often 
in infants with SD. Fifteen infants with SD were believed to be neurologically 
normal at the time of nursery discharge. These findings suggest the importance 
of prenatal factors in optimally treated preterm infants in whom SD develops.