Purpose: To find the relation between maternal serum levels of Iron, Folic acid & vitamin B12 and weight gain with birth weight of newborn. Methods: A prospective observational study on 100 pregnant women was carried out in the GMH Rewa and peripheral health centres like PHC, CHC, CH, & DH. Their blood parameters and weight gain were analysed and noted in successive 2nd & 3rd trimesters then correlates with the pregnancy outcome, i.e., newborn birth weight. Results: Out of 100 pregnant women, In 2nd trimester of pregnancy, 12(12%) had inadequate weight gain which has 46(46%) low birth weight newborn and, 54(54%) had low maternal serum iron level which has 46(46%) low birth weight newborn. In 3rd trimester, 3(3%) of pregnant women had inadequate weight gain have 46(46%) low birth weight newborn, 83(83%) had low serum iron level have 46(46%) low birth weight newborn. Conclusion: Nutrition along with important micronutrients level, especially Iron, during pregnancy affects health status of mother, weight gain and newborn birth weight