Changes in the coefficient variations of live birth weight in Japan, 1969-1985

The present study was conducted on changes in the coefficient variations of live birth weight and in the proportion of singleton live birth weight by gestational age using vital statistics compiled by the Japanese government from 1969 to 1985. The coefficient variations of live birth weight declined between 1969 and 1977-78 and then increased. The coefficient variations of live birth weight were affected by the percentage of low birth weight infants. The decline in the coefficient variations depends on the decrease of low birth weight infants, while the increase in the coefficient variations depends on the increase of low birth weight infants. Recently, the proportion of low birth weight infants has increased in Japan. Perinatal mortality rates, which indicate the level of maternal and child health, have decreased annually.