Risk Factors for Low Birth Weight Infants in Japan

Prevalence of low birth weight infants in Japan has been increasing, although infant mortality is the lowest in the world. We conducted a population based case-control study to clarify risk factors for low birth weight infants in Japan. Information was obtained by questionnaire. The response rate was 78.9% from 402 cases and 804 controls. The majority of low birth weight infants belongs to full-term case group. This is considered to be an important factor for low infant mortality in Japan. We examined potential risk factors by a multiple logistic regression model. Lower maternal academic career and toxemia were identified as significant risk factors for pre-term low birth weight infants, while maternal shorter height, lower prepregnancy weight, maternal smoking and employment during pregnancy and hypertension were identified as significant risk factors for full-term low birth weight infants. The Japanese small physique and prevalent hypertension are considered to be causes for the high prevalence of low birth weight infants. J Epidemiol, 1994; 4: 91-98.