Changes in renal function during pregnancy. Kidney function also dramatically increases during pregnancy. The rapid developing rise in renal blood flow and glomerular filtration rate were documented in careful studies undertaken in humans. These increments average between 40 and 50%. Dr. Davison and his associates found that these improvements in renal hemodynamics occurred even prior to the changes in cardiac output and plasma volume. GFR: glomerular filtration rate. ERPF: effective renal plasma flow [8].