Abstract
Perinatal mortality rates have been markedly reduced in Japan (Ministry of Health and Welfare, 1986). Perinatal deaths were most closely related to fetal age and weight. The infants of short gestational duration and lowbirth weight have been found to show high perinatal mortality rates (Erhardt et al., 1964; Yerushalmy 1970; Behrman et al., 1971). The reduction in perinatal mortality rates was greatest for large birth weight infants(Makino et al., 1985). Birth weight was as sociated with gestational age (Erhardt et al., 1964). Perinatal mortality by gestational age differed according to cause of death. Therefore, it is considered to be important to observe the changes in cause specific Perinatal mortality rates by gestational age. The purpose of this paper is to study the association between decrease in perinatal mortality rates and gestational age.
