Background
: Low birth weight is the most important determinant of the newborns morbidity and mortality and the healthy growth and development. Pregnancy can be seen as a time when the family's bounderies are shifting to accommodate a new member. Accordingly each family member can be affected from altered family function. Therefore we carried out this study to determine the effects of family functions on infant birth weight.

Methods : Randomly selected mothers in AnDong General Hospital and SungSo Hospital obstetric clinics who visit for delivery were invited to participate this study from May through June 1994. The mothers perception of family function was assesed with FACESⅢ and collects sociodemographic, biomedical data. 289 mother-infant pair out of 303 complete questionnares(exception congenital anomaly, multiple pregnancy, placenta or uterine anomaly, preterm) were studies. Infant body weight and other variables affecting body weight were compared by family function type.

Results : Infant body weight is positively related with gestational age, maternal BW, weight gain during pregnancy and negatively related with prematurity delivery history, alcohol. 84.8% of family were considered functional and family function averages flexibly separated. There were no statisfically significant difference in this analysis between sociodemographic determinants(education level, occupation, religion, income, marrige, smoking et al) and biomedical characteristics(gestational age, prepregnancy weight and weight gain during pregnancy, hypertension) of functional and dysfunctional families. Infant body weight from with dysfunctional family significantly smaller than from whose mother with functional families(P<0.05).

Conclusion : Infant birth weight can be influenced by family function or its associated factors and dysfunctional family increases low birth weight also. Family dysfunction should be possible to intervene early in pregnancy to modify risk factors associated with family systems. So that it will be helps decrease low birth weight.