Renal Changes in Pregnancy

Pregnancy changes the renal system in two linked ways: increased cardiac output and systemic vasodilation increase renal blood flow and glomerular filtration, while the enlarging uterus and hormonal effects dilate the collecting system. The expected result is a lower serum creatinine and some urinary stasis—not renal failure. That distinction matters at the bedside. A creatinine that looks acceptable on a nonpregnant reference range may already be abnormal in pregnancy, and urinary frequency or mild glucosuria may be physiological. Conversely, urinary stasis can allow an initially silent infection to ascend, and hypertension or a rising creatinine can signal renal involvement in a hypertensive disorder of pregnancy.