[What is the present best scale to estimate infants' prematurity to predict retinopathy of prematurity? Aichi Retinopathy Study Group].

The present study is the second report using the data of the epidemiological survey of retinopathy of prematurity (ROP) obtained during the 2 year period 1986-1987 in Aichi Prefecture. To study ROP we have used birthweight and gestational age for estimation of infants' prematurity. These two parameters were found to have a very close relation with the incidence of ROP. Although gestational age is close to the embryonic age, birthweight is greatly influenced by intrauterine environmental factors. To confirm the importance of using birthweight, the relationship between the incidence of ROP and the influence of intrauterine environmental factors must be close. Using data on 1,887 premature infants, the mean and standard deviation of birthweight in each gestational weeks were calculated. Deviation of birthweight was considered to reflect the influence of intrauterine environmental factors and was evaluated by comparing the birthweight of a baby with the mean birthweight for the same number of gestational weeks. The incidence of ROP had no close relationship with the deviation of birthweight at each gestational age. Therefore, it was concluded that the influence of the modifying factors of birthweight had not any close relation with the incidence of ROP. At present we should use gestational age as the best scale to estimate infants' prematurity to predict ROP.