van Balen VAL, et al. - Researchers sought to estimate the extent of adaptation over the course of both healthy physiological and complicated singleton pregnancies via systematically reviewing the current literature on kidney function changes during pregnancy. In addition, they examined healthy pregnancy reference values. Searching PubMed (NCBI) and EMBASE (Ovid) electronic databases, they identified 29 eligible studies for inclusion in the analysis. In a healthy pregnancy, an increase in the kidney function, quantified by GFR measured either by inulin clearance or creatinine clearance, was observed as early as the first trimester, as compared with non-pregnant values. Throughout gestation, they continuously observed a higher rate the kidneys function. In contrast, patients with hypertensive pregnancy show a decrease in kidney function. Although changes in the upper limit of the reference curve occur throughout gestation, from a clinical perspective, they suggest considering serum creatinine (SC) above 0.75 mg/dL (66 µmol/L) as abnormal at all gestational ages.