Trends in the prevalence of low birth weight in Okinawa, Japan: a public health perspective

Aim: To review the trends in low birth weight (LBW) in Japan and Okinawa and to discuss the public health implications of the trend. Methods: The statistical records of Japan and the Okinawa prefecture were reviewed to observe secular trends of LBW incidence rate and other health indicators. Literature researches were undertaken of English and Japanese language publications to complete the review. Results: The LBW rate in Japan declined until the 1970s, reaching a low point for the whole country in 1978-1979 when it was 5.2% (7.2% in Okinawa). In Okinawa the proportion of LBW declined from 8.1% in 1973 to 7.2 in 1978. Since 1980 the LBW rate has steadily increased to its current level of 9.3% in Japan and 10.9% in Okinawa. During this period, the prematurity rate has not increased and other indicators of child health have continued to improve. Conclusion: Japan is unique among developed countries in that the LBW rate has almost doubled in the past three decades and the rate in Okinawa is 20% greater than the mainland. The health costs of this trend include the neonatal care of LBW infants and the increased risk of chronic disease in later life.