Aim: To evaluate the effect of Pre-eclampsia on platelet count in the pregnant Women. Material and methods: This case control study was carried out in the Department of Pathology, Patna Medical College and Hospital Patna, Bihar, India from December 2018 to November 2019. Total 200 patients were divided in two groups as Cases and Control. Cases study group includes 100 females with the thrombocytopenia and Control includes 100 females without thrombocytopenia. Results: The Most affected age group in which thrombocytopenia seen was between 20 to 25 years. In women with thrombocytopenia with mild Pre-eclampsia Platelet Count (x109 /L) was 65-288 , thrombocytopenia with Severe Pre eclampsia Platelet Count (x109 /L) was 27- 259 and women without thrombocytopenia had normal Platelet Count. Conclusion: Clinically platelet indices can be a useful screening test for early identification of preeclampsia and eclampsia. Also platelet indices can assess the prognosis of this disease in pregnant women and can be used as an effective prognostic marker because it correlates with severity of the disease. Platelet count is a simple, low cost, and rapid routine screening test.