Objectives We aimed to assess cognitive function in women with pre-eclampsia stratified by severity, before and after onset of disease. Design Prospective case control study Setting Single center study at a referral hospital in Cape Town, South Africa. Population Pregnant women between 20 and 42 weeks gestation with eclampsia, pulmonary oedema, pre-eclampsia without severe features a normotensive pregnancy. Methods Women were included at diagnosis (cases) or at admission for delivery (controls). Two cognitive assessments, the Cognitive Failure Questionnaire (CFQ) to assess the cognitive function subjectively before inclusion in the study, and Montreal Cognitive Assessment (MoCA) to assess the current cognitive function objectively before discharge from the hospital after delivery were performed. Main outcome measures Total- and subscores from the CFQ and MoCa tests. Results We included 61 women with eclampsia, 28 with pre-eclampsia complicated by pulmonary oedema, 38 with pre-eclampsia without severe features and 26 with normotensive pregnancies. There was no difference in cognitive function from early pregnancy between groups. Women with eclampsia and pre-eclampsia complicated by pulmonary oedema scored lower on the MoCA assessment at time of discharge compared to women with normotensive pregnancies. The results were attenuated in pulmonary oedema after adjustment for confounders. Conclusion Women with pre-eclampsia complicated by pulmonary oedema and in particular eclampsia had impaired cognitive function after onset of disease compared to normotensive pregnant controls. The impairment did not seem to be present before onset of disease. Women with pre-eclampsia without severe features did not have impaired cognitive function.