van Balen VAL, et al. - Researchers sought to estimate the extent of change in kidney function over the course of both healthy physiological and complicated singleton pregnancies and to ascertain healthy pregnancy reference values. Searching PubMed (NCBI) and EMBASE (Ovid) electronic databases, they identified 29 eligible studies for inclusion in the analysis. Outcomes revealed an increase in glomerular filtration rate (GFR) as early as the first trimester in a healthy pregnancy; GFR was increased by up to 40–50% in physiological pregnancy when compared with non-pregnant values. In uncomplicated pregnancy, highest inulin clearance was noted at 36–41 weeks, with a 55.6% increase when compared with non-pregnant values, and highest creatinine clearance was noted at 15–21 weeks' gestation, with a 37.6% increase. Serum creatinine level reduces most prominently at 15–21 weeks in uncomplicated pregnancy, with a 23.2% decrease when compared with non-pregnant values. Throughout gestation, the higher kidney function was evident. In contrast, in hypertensive pregnancy, they observed decreased kidney function.