Background: Low birth weight (LBW) (<2500 g), is the strongest determinant of infant morbidity and mortality. The aim of this study was to find the association of medical illness in mother during pregnancy with low birth weight in newborn. Methods: The present study design was a community based cross–sectional study. It was conducted in an urban area of Jamnagar, Gujarat from Jan to Dec 2016. The study population included 400 mothers and their newborns residing in the study area. The pregnant women were interviewed using predesigned and pretested structured questionnaire. Results: The maternal medical illnesses found to be significantly associated with low birth weight of newborns in our study were Anemia (p 0.000), PIH (p 0.000),APH (p 0.001). Conclusion: To conclude the present study Maternal medical illnesses including gestational hypertension, APH and Anemia were found significantly associated with LBW.