Proteinuria in pregnancy: Evaluation and management
- Ravi I Thadhani, MD, MPH
Ravi I Thadhani, MD, MPH
- Professor of Medicine
- Harvard Medical School
- Sharon E Maynard, MD
Sharon E Maynard, MD
- Associate Professor of Medicine
- Morsani College of Medicine
- University of South Florida
In non-pregnant individuals, abnormal total protein excretion is typically defined as greater than 150 mg daily. In normal pregnancy, urinary protein excretion increases substantially; hence, total protein excretion is considered abnormal in pregnant women when it exceeds 300 mg/24 hours .
Proteinuria is one of the cardinal features of preeclampsia (table 1), a common and potentially severe complication of pregnancy. However, two important points should be noted. First, the severity of proteinuria is only weakly associated with adverse maternal and neonatal outcomes, and should not be used to guide management [2-5]. Second, proteinuria may be absent: Up to 10 percent of women with clinical and/or histological manifestations of preeclampsia and 20 percent of women with eclampsia have no proteinuria at the time of initial presentation [6,7]. These observations are reflected in the 2013 American Society of Obstetrics and Gynecology Task Force on Hypertension in Pregnancy recommendations, which no longer require proteinuria for the diagnosis of preeclampsia if other severe preeclampsia features are present (table 1). (See "Preeclampsia: Clinical features and diagnosis".)
Although less prevalent, primary renal disease and renal disease secondary to systemic disorders, such as diabetes or primary hypertension (formerly called “essential” hypertension), are usually characterized by proteinuria and may first present in pregnancy. To further complicate this picture, 20 to 25 percent of women with chronic hypertension and diabetes develop superimposed preeclampsia [8,9].
It is important for clinicians caring for pregnant women to understand how to identify proteinuria, and how to determine whether preeclampsia or renal disease (or both) is the cause. This topic will discuss the approach to the evaluation of pregnant women with proteinuria and management of nephrotic syndrome in pregnancy. The evaluation of proteinuria in nonpregnant individuals and measurement of protein excretion are discussed in detail separately. (See "Assessment of urinary protein excretion and evaluation of isolated non-nephrotic proteinuria in adults".)
RENAL CHANGES IN NORMAL PREGNANCY
Glomerular filtration rate (GFR) and renal blood flow rise markedly during pregnancy, resulting in a physiologic fall in the serum creatinine concentration. Urinary protein excretion increases substantially due to a combination of increased GFR and increased permeability of the glomerular basement membrane . Additionally, tubular reabsorption of filtered protein is reduced in pregnancy, along with other nonelectrolytes, such as amino acids, glucose, and beta-microglobulin. (See "Assessment of urinary protein excretion and evaluation of isolated non-nephrotic proteinuria in adults".)
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- RENAL CHANGES IN NORMAL PREGNANCY
- SCREENING FOR PROTEINURIA
- QUANTIFYING PROTEIN EXCRETION
- 24-hour collection
- Urine protein to creatinine ratio
- Urine albumin to creatinine ratio
- 8- or 12-hour collection
- DIFFERENTIAL DIAGNOSIS OF PROTEINURIA
- Renal disease versus preeclampsia
- Superimposed preeclampsia
- Nephrotic syndrome
- - Kidney biopsy in pregnancy
- MANAGEMENT OF NEPHROTIC SYNDROME IN PREGNANCY
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS