Pregnancy is associated with a variety of anatomic and functional changes of the kidneys and lower urinary tract. Caliceal, pelvic, and ureteral dilatation occurs during the first trimester and persists throughout gestation up to 12 weeks postpartum. Hydronephrosis and hydroureter have direct clinical consequences because urinary stasis contributes to the propensity to develop pyelonephritis in women with asymptomatic bacteriuria.

The most significant alteration in renal function during pregnancy is a progressive increase in the glomerular filtration rate, which begins as early as 2 weeks’ gestation. Creatinine and urea production do not increase during pregnancy. Therefore a serum concentration of creatinine and urea considered normal for a nonpregnant woman may be elevated in the gravida and should be investigated.

Acute renal failure during pregnancy most often results from severe preeclampsia or eclampsia. Management of acute renal failure during pregnancy is essentially the same as that for nonpregnant patients. Particular attention should be given to fluid and electrolyte balance and adequate nutrition.

Many women with chronic renal disease have diminished fertility. Nevertheless, some patients with moderately severe disease and some who have received renal transplants do conceive. The major determinants of pregnancy outcome in women with chronic renal disease are the presence of hypertension and the severity of pregestational renal insufficiency. The severity of renal insufficiency has a direct effect on the outcome of pregnancy. Pregnancies in women with a pregestational serum creatinine concentration greater than 1.5 mg per deciliter or a creatinine clearance less than 70 to 80 ml per minute are associated with an increase in perinatal mortality and the onset or worsening of hypertension.