Objective(s): The present study was performed to determine relationship between maternal nutrition status and infantschr('39') birth weight. Maternal nutrition status was assessed by pre-pregnancy body mass index (BMI), weight gain, intake of iron and folic acid supplements during pregnancy. Methods: This case-control study was included 46 cases (women who had delivered low birth weight infants) and 92 controls (women who had delivered infants with more than 2500 gr). They were selected from population who received prenatal cares from health care centers in south of Tehran. Data were collected from present documents in the centers and completed by telephone interviewing. Then data were analyzed in spss13 by t-test or χ2. Crude odd ratios and 95% confidence intervals were calculated. Results: There was no difference between maternal jobs, age, parity, birth interval, and delivery type in case and control groups. Weight gain (P<0.001) and intake of iron supplement (P<0.05) were less in cases as compared with control group. Weight gain during pregnancy was found to reduce risk factors for delivery LBW infants (OR=3.77, %95 CI: 1.7-8.1). Conclusion: Suitable weigh gain and intake of iron supplement decrease the risk of low birth weight infants.