BackgroundPreeclampsia is a major factor in both maternal and fetal morbidity and mortality. The most widely investigated preeclampsia prevention medication is low dose Aspirin. However, guidelines differ considerably regarding the prophylactic dose of Aspirin for preeclampsia.ObjectiveThe objective is to compare the efficacy of 150mg versus 75mg Aspirin for the prevention of preeclampsia in pregnant women at high risk of preeclampsia.MethodologyThis was a parallel, open-label, randomized control trial carried over a period of one year and three months at a tertiary care center of Eastern India. Block randomization was done and block sizes of 2 and 4 were used to ensure balanced distributions within the study arms. Primary outcome was the development of preeclampsia and secondary outcomes were fetomaternal complications in both groups.ResultsThe present clinical trial was conducted on 116 pregnant women with a risk factor of preeclampsia and they were randomly assigned to receive either 150mg or 75mg of Aspirin daily beginning from 12 to 16 weeks of gestation till 36 weeks' gestation. A significantly greater number of pregnant females who received Aspirin 75mg (33.92%) developed preeclampsia in contrast to those who received Aspirin 150mg (8.77%), p=0.001, OR = 5.341, 95%CI = 1.829-15.594. There was an insignificant difference in fetomaternal outcome among both the groups of women.ConclusionAmong women who are at high risk of developing preeclampsia, Aspirin 150 mg once a day at bedtime is more effective than Aspirin 75 mg once a day at bedtime in preventing preeclampsia with similar fetomaternal outcomes (NICU admission, IUGR, neonatal death, still birth, eclampsia, HELLP syndrome, placental abruption and pulmonary edema).