Background: Before the discovery of Rh system, little was known about the aetiology of erythroblastosis fetalis. Rhesus (Rh) incompatibility refers to the discordant pairing of maternal and fetal Rh type. It is associated with carrying a Rh-positive fetus, which can result in consequences along the spectrum of HDN ranging from self-limited hemolyticanemia to severe hydrops fetalis.Hence; this study was conducted to assess the Prevalence of Rh-negative blood group and fetomaternal outcome in Rh negative pregnancy.Material and methods: A prospective observational study was carried out in 60 patients who were attending antenatal clinic and were admitted in obstetric unit of Department of Obstetrics and Gynaecology in K.M.Medical College and hospital Mathura. They were investigated from October 2022 to November 2023. On admission, history of the patients was taken regarding her age, address and occupation, Menstrual history and detailed obstetrical history was taken regarding gravidity, parity, abortion, D&C following abortion and number of living term and preterm issues. Any history of neonatal Jaundice in previous children and if present type of treatment if required and outcome of such a neonate,number of still births and history of hydrops foetalis in previous pregnancies and all ANC routine investigations were done.Results: Of the total 60 cases, maximum cases 55 delivered at 37-40 weeks, 1cases delivered after 40 weeks and 4 patients delivered between 30-37 weeks. Maximum cases delivered normally, 10 required caesarean section and 2 had forceps delivery. 8 Rh negative mothers had preeclampsia /PIH, 3 had abruption placentae, 2 had oligohydramnios and 1 had polyhydramnios, 4 had preterm delivery, 1 had still birth and 1 baby had NNHB Whose mother had oligohydramnios.There was no incidence of Isoimmunisation found in present study.Conclusion: Significant progress in medical services and technology over the past few decades has transformed the management of Rh disease. The advent of procedures such as amniocentesis and the spectrophotometric analysis of amniotic fluid has enabled effective monitoring of pregnancies, allowing for timely interventions that optimize perinatal outcomes. Early identification of the condition, particularly through the detection of elevated antibody titers, is critically important.