How is proteinuria managed in obstetrics?

Management of Proteinuria in Obstetrics

Proteinuria in obstetrics should be assessed initially by automated dipstick urinalysis followed by protein/creatinine ratio if positive, with a ratio ≥30 mg/mmol (0.3 mg/mg) considered abnormal and diagnostic of significant proteinuria. 1

Diagnosis and Assessment of Proteinuria

Screening and Quantification

• Initial screening should be done with automated dipstick urinalysis when available
  • If positive (≥1+, 30 mg/dL), proceed to quantitative assessment
  • A negative dipstick test can usually be accepted without further testing at that time 1

Quantitative Assessment

• Spot urine protein/creatinine (PCr) ratio is the preferred method
  • PCr ratio ≥30 mg/mmol (0.3 mg/mg) is considered abnormal 1, 2
  • This eliminates difficulties with 24-hour collections and speeds up decision making
• 24-hour urine collection:
  • Traditional gold standard (≥300 mg/24h considered abnormal)
  • Still indicated to confirm nephrotic syndrome which has implications for thromboprophylaxis 1
  • Should include creatinine measurement to assess collection adequacy

Clinical Significance

• Proteinuria is not required for diagnosis of preeclampsia according to current guidelines 1, 3
• Massive proteinuria (>5 g/24h) is associated with worse neonatal outcomes 1, 2
• The amount of proteinuria does not reliably predict maternal outcomes and should not be used alone to guide delivery timing 3

Management Based on Clinical Context

New-Onset Proteinuria After 20 Weeks

1. Initial Assessment:

   • All women with preeclampsia should be assessed in hospital when first diagnosed 1
   • Complete evaluation including:
     • Blood pressure monitoring
     • Laboratory tests (hemoglobin, platelet count, liver and renal function tests)
     • Fetal assessment

2. Ongoing Monitoring:

   • Maternal monitoring should include:
     • BP monitoring
     • Clinical assessment including clonus
     • Minimum twice weekly blood tests 1
   • Fetal monitoring should include initial assessment and serial surveillance if growth restriction is present 1, 2

3. Management Decisions:

   • Some women may be managed as outpatients once their condition is stable 1
   • Delivery is indicated at 37 weeks or if complications develop:
     • Repeated episodes of severe hypertension despite treatment
     • Progressive thrombocytopenia
     • Abnormal renal or liver enzyme tests
     • Pulmonary edema
     • Neurological complications
     • Non-reassuring fetal status 1

Proteinuria with Severe Hypertension

• Antihypertensive treatment should be initiated to keep SBP <160 mmHg and DBP <110 mmHg 1
• Acceptable agents include oral methyldopa, labetalol, oxprenolol, and nifedipine 1
• Magnesium sulfate should be administered for seizure prophylaxis 1, 2
• All women with severe pre-eclampsia should be delivered promptly, regardless of gestational age 1

Proteinuria in Women with Pre-existing Renal Disease

• Baseline assessment of renal function should be done before conception 2
• Proteinuria documented before 20 weeks suggests pre-existing renal disease 4
• Hyperfiltration during pregnancy may lead to increasing proteinuria, making diagnosis of superimposed preeclampsia challenging 5
• The acute onset of proteinuria and worsening hypertension in women with chronic hypertension suggests superimposed preeclampsia 4

Postpartum Management

• All women with hypertension in pregnancy should have BP and urine checked at 6 weeks postpartum 1
• Persistent hypertension should be confirmed by 24-hour ambulatory monitoring 1
• Reassess proteinuria at 3 months postpartum to check for persistent proteinuria, which may indicate underlying renal disease 2
• Women with persistent hypertension or proteinuria 6 weeks after delivery should be referred to a specialist 1
• Women with preeclampsia have increased long-term cardiovascular risks and should have annual medical review 2

Important Clinical Considerations

• Proteinuria fluctuates widely in preeclampsia due to its vasospastic nature 4
• Hypertension or proteinuria may be absent in 10-15% of patients with HELLP syndrome and in 38% of patients with eclampsia 4
• Women with gestational proteinuria should be closely monitored as a substantial portion (25%) progress to preeclampsia 6
• High proteinuria level ≥2 g/day is a major predictor for progression to preeclampsia 6
• The level of proteinuria should not guide management decisions; other variables such as blood pressure control, organ damage, and neurological involvement are more reliable indicators of preeclampsia severity 7