[Analysis of factors associated with the occurrence of low birth weight infants]

The relationship between low birth weight infants (LBW) and 3 perinatal factors; pre-pregnant maternal Body Mass Index (BMI: Quetelet's index), maternal height and parity was investigated by the log-linear analysis, using the birth records of an obstetric facility at Naha city. In this facility there were 4,894 deliveries from Jan. 1978 to Dec. 1987. Of the 4,894 infants, 4,142 were live singletons with available data for the analysis. The odds ratio of each risk factor was calculated by the log-linear model. Women with lower pre-pregnant BMI (less than 20) had an increased LBW risk by 1.80 (95% CI: 1.32-2.43) compared to women with higher pre-pregnant BMI (20 less than). Lower maternal height (150 cm greater than) was associated with significant LBW risk (1.47; 95% CI: 1.03-2.12). Primiparae had higher LBW risk than multiparae (1.68; 95% CI: 1.25-2.28). In this analysis we evaluated the interaction effects on LBW occurrence of the three factors and found no interaction effects among them.