Abstract Background and Aims The adverse effects of chronic kidney disease on pregnancy and pregnancy on renal function have been described, but the effect of severe proteinuria in early pregnancy is not known. The aim of this study was to evaluate the obstetric and renal outcomes of pregnant women with severe proteinuria manifesting in early pregnancy. Method We retrospectively assessed the records of over 400 women with renal disease who were cared for during pregnancy in Queen Charlottes and Chelsea hospital and identified women with nephrotic range proteinuria in early pregnancy. Their records were reviewed and outcomes were compared to women with CKD and little or no proteinuria in early pregnancy. Results The study included 99 women with renal disease, of these 37 with severe proteinuria, and 62 patients who had mild or no proteinuria. The baseline GFR and blood pressure in the groups was similar. There were significantly more women with glomerular diseases in the group with proteinuria. The group with severe proteinuria had significantly higher rates of delivery by C-section, and prematurity including severe prematurity (<34 weeks). They had lower average birth weight and more babies born with very low birth weight. Their renal outcomes were poorer, with a lower eGFR at 3 years and a higher rate of advanced CKD and renal replacement therapy. In the women with proteinuria, the level of scarring on renal biopsy was found to be a significant predictor of several poor outcomes, including premature birth and developing advanced kidney disease. Conclusion Severe proteinuria early in pregnancy is associated with lower birth weight, greater prematurity and poorer renal function in the long term. Physicians treating these women must be aware that they are at a higher risk of complications than women with renal disease without severe proteinuria.