Periventricular leukomalacia is recognized as the leading cause of cerebral palsy in preterm infants. To clarify the prevalence of periventricular leukomalacia and cerebral palsy in Japan, a nationwide survey was performed. The prevalence of periventricular leukomalacia in the group of surviving preterm infants of gestational ages less than 33 weeks born in 2007 was 2.7% (78/2883) on ultrasound diagnosis, and 3.3% (92/2824) on magnetic resonance imaging. The prevalence of cerebral palsy was 4.3% (125/2883) on clinical diagnosis. In our previous study, the prevalences of periventricular leukomalacia in 1990-1991, 1993-1994, 1996, and 1999 were 4.8%, 4.9%, 4.9%, and 5.3% on ultrasound, and 7.9%, 7.7%, 6.9%, and 7.3% on magnetic resonance imaging, respectively. The prevalence of periventricular leukomalacia has decreased significantly in Japan.
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