INTRODUCTION: Preeclampsia is associated with increased maternal and neonatal morbidities and mortalities. These include placental abruption, eclampsia, acute renal failure, cerebrovascular accident, preterm births and its sequelae. It is therefore important to ensure an accurate method of preventing the complications from this condition. AIM:To assess the efficacy of low dose aspirin in preventing preeclampsia and improving fetal outcome among pregnant women at risk DESIGN: A double blind randomised controlled study. SETTING: The study was conducted at the Department of Obstetrics and Gynaecology, University of Ilorin Teaching Hospital, Ilorin, Kwara state, Nigeria. STUDY POPULATION: Pregnant women at 12-20 weeks of gestation with risk of developing preeclampsia on low dose aspirin tablets while controls were pregnant women with same risk factors on placebo. METHODS: A total of two hundred and seventy six pregnant women at 12-20 weeks of gestation were recruited for the study but data for two hundred and sixty five women was obtained and analysed. Seven of the participants did not comply with the drugs and four were lost to follow up. Group I consisted of one hundred and thirty consenting pregnant women on low dose aspirin while one hundred and thirty five of the participants served as controls on placebo (group II). They all had either low dose aspirin tablets or placebo ingested and monitored till 6 weeks post partum .Blood pressures and urinalysis/24-hour urine protein estimation done at each visit as required and the findings was compared between the two groups to determine the efficacy of low dose aspirin in the prevention of preeclampsia and perinatal outcomes.