Background : Due to controversies in etiology of malnutrition, mother’s BMI and child’s sex, the present study was conducted in order to determine the role of mother’s BMI and child’s sex on malnutrition of children younger than 5 years old that referred to health care centers in Kashan in 2002-2003.

Materials and Methods : In a case-control study using cluster and random sampling,125 children with malnutrition based on weight for age using -2 standard deviations criteria NCHS (case group) and 125 children without malnutrition (control group), from 10 health centers in Kashan were enrolled during the study period. Mother’s BMI and child’s sex was compared in two groups. Case and control groups were matched in confounding variables.�Information was obtained from medical records through interview . Results were judged with Chi- square, t-test and mantel haenszel. Also Odd's ratio and confidence interval were determined.

Results : Results showed that matched factors such as maternal age, maternal employment, parity, birth weight and height, duration of breastfeeding and child age were similar in two groups. Mean mother’s BMI was significantly different in two groups (P<0.002). Also results demonstrated child’s sex was related to malnutrition, (P<0.02). Odd's ratio and confidence interval for effect of BMI<22 and female sex on malnutrition were ) OR=2.1 CI=3.74-1.16 P<0.05, OR=1.81 CI=3.05 -1.07 P<0.05) respectively. Although malnutrition was showed to be related to each variable separately, mantel haenszel test demonstrated that two factors were not concurrently related to malnutrition.

Conclusion : Low mother’s BMI and female sex, increased risk of malnutrition alone but not related with malnutrition together. Further studies are recommended to determine other risk factors.