Urinary protein excretion is considered abnormal in pregnant women when it exceeds 300 mg/24 hours at anytime during gestation, a level that usually correlates with 1+ on urine dipstick. Proteinuria documented before pregnancy or before 20 weeks’ gestation suggests preexisting renal disease. The National High Blood Pressure Education Program Working Group recommended that that the diagnosis of proteinuria be based on the 24-hour urine collection. Preeclampsia is the leading diagnosis that must be excluded in all women with proteinuria first identified after 20 weeks of gestation. Given the vasospastic nature of this condition, when it is present, the degree of proteinuria may fluctuate widely from hour-to-hour. Hypertension or proteinuria may be absent in 10–15% of patients with HELLP syndrome and in 38% of patients with eclampsia. The acute onset of proteinuria and worsening hypertension in women with chronic hypertension is suggestive of superimposed preeclampsia, which increases adverse outcomes. However, because proteinuria is not independently predictive of adverse outcome, an exclusive proteinuric criterion as an indication for preterm delivery in preeclampsia should be discouraged.
Obstetricians & Gynecologists, Family Physicians
After completion of this article, the reader should be able to state that measurement of urinary protein levels by simple techniques are not sensitive or specific, recall that both hypertension and proteinuria may be absent in patients with preeclampsia, and explain that proteinuria is not predictive of adverse outcomes and that delivery should not be based on protein excretion alone.