Objectives: To investigate the outcome of preterm infants and the prevalence of cerebral palsy and to examine the relevance between clinical risk factors, ultrasonographic abnormalities and the development of cerebral palsy.

Methods
From January, 1993, to December, 1994, we selected and followed up 437 cases of survived preterm infants born in Seoul National University Hospital. Clinical risk factors such as gestational age, birth weight, maternal complications, birth asphyxia, and neonatal sepsis were evaluated. Sequential ultrasonographic observations were done at the interval of 7 or 10 days. Ultrasonographic abnormalities could be classified into periventricular echodensity, periventricular leukomalacia (PVL) including cystic PVL, intraventricular hemorrhage, ventriculomegaly and brain atrophy. Diagnosis of the cerebral palsy was confirmed after the follow up more than 2 years after birth, and the correlations of ultrasongraphic abnormalities with clinical types and severities of cerebral palsy were analyzed.

Results
Twenty one cases (4.8%) among survived infants were diagnosed as a cerebral palsy. The prevalence of cerebral palsy was 20% in infants with less than 32 weeks of gestation, and 1.4% after 34 weeks. The prevalence of cerebral palsy was 12% in infants with less than 2000 g of birth weight, while, 0.4% in more than 2000 g of birth weight. Mother's age, primiparaty, and history of abortion did not influence the prevalence of cerebral palsy, but preterm labor, preterm rupture of membrane, severe birth asphyxia, neonatal sepsis, and respiratory distress syndrome were significantly relevant to the increased prevalence of cerebral palsy. Fifty six percents (18/32) of PVL (100% of cystic PVL) and 53% (7/13) of third grade IVH progressed to a cerebral palsy. Without PVL, third grade IVH had no explicit correlation with a cerebral palsy. Multiple logistic regression analysis of clinical risk factors and ultrasonographic abnormalities revealed that PVL is a determinant and independent risk to the cerebral palsy. Most cases turned out a spastic diplegia. The cases with cystic lesions especially showed the worse clinical outcomes.

Conclusion
Four point eight percents of survived preterm infants developed a cerebral palsy. The existence of PVL was the most important risk factor among the perinatal problems and ultrasonographic abnormalities.