Outcome of infants born preterm, with special emphasis on extremely low birthweight infants.

The outcome of extremely low birthweight (ELBW) infants has been reviewed from published articles and up-to-date data from Japan. The mortality rate of these infants declined significantly from over 90% to below 50% after the introduction of intensive care in the 1970s, but the incidence of major neurological sequelae remained steady at around 20%. Similarly, the incidence of major neurological sequelae did not increase along with the decrement of birthweight, although the mortality rate increased significantly. Long-term follow-up of ELBW children until school age has revealed poor school performance in spite of the absence of major neurological sequelae and the attainment of average intelligence quotient scores. Physical growth is retarded initially but generally catches up by the age of 8-9 years. In Japan, the neonatal mortality rate of ELBW infants declined from 56% in 1981 to 25% in 1989 with an increased birth rate of ELBW infants. In ELBW infants cared for at Tokyo Women's Medical College during 1984-90, the survival rate was 112 out of 134 (84%) and the incidence of major neurological sequelae was 15 out of 87 (17%) at 1-8 years old. The viability limit of ELBW infants has been discussed based on recent data. As a result of the rapid progress of medical care of ELBW infants, their viability limit as defined in the Eugenic Protection Law in Japan was amended from 24 completed weeks of gestation to 22 completed weeks in 1991.