Proteinuria in Pregnancy

Proteinuria in pregnancy is protein in the urine at a level above 300 mg in 24 hours or a urine protein to creatinine ratio above 30 mg/mmol. Causes include preeclampsia, urinary infection, contamination, chronic kidney disease, glomerulonephritis, diabetic nephropathy and lupus nephritis. It matters because new proteinuria after 20 weeks with hypertension is preeclampsia, which needs urgent care.

• Dipstick 1 plus or more needs confirmation with a ratio.
• Trace proteinuria is common in normal pregnancy.
• Proteinuria before 20 weeks suggests kidney disease.

Most women have no symptoms. Others have oedema, foamy urine, headache, visual change, upper abdominal pain or dysuria, depending on the cause. Check blood pressure at every visit.

• Hypertension with proteinuria after 20 weeks suggests preeclampsia.
• Fever and loin pain suggest infection.
• Differential diagnosis: preeclampsia, urinary tract infection, vaginal contamination, chronic kidney disease, glomerulonephritis, lupus nephritis, diabetic nephropathy, orthostatic proteinuria.
• Complications: preeclampsia and eclampsia, kidney damage, preterm birth, growth restriction, nephrotic syndrome, thrombosis.

The approach is quantification and a search for the cause.

• Urine protein to creatinine ratio on a midstream sample (above 30 mg/mmol is significant) or 24 hour urine protein above 300 mg.
• Urinalysis with microscopy and culture; repeat dipstick after cleaning the perineum.
• Blood pressure, full blood count, creatinine, liver enzymes, lactate dehydrogenase, uric acid, albumin.
• Antinuclear antibody, complement, HbA1c, HIV and hepatitis tests when kidney disease is suspected; renal ultrasound.

The principle is to treat the cause, with immediate care for preeclampsia.

• Supportive: rest; control blood pressure; daily fetal movement counts; weigh daily; monthly urine culture if chronic kidney disease.
• Pharmacological: urinary infection: cefalexin 500 mg oral 6-hourly for 7 days; preeclampsia: aspirin 150 mg oral at night, labetalol 200 mg oral every 8 to 12 hours (maximum 2.4 g daily) or nifedipine modified release 30 to 60 mg daily (maximum 120 mg) for blood pressure above 140/90 mmHg, labetalol 20 mg IV then 40 mg, 80 mg and 80 mg at 10 minute intervals (maximum 220 mg) for blood pressure above 160/110 mmHg, magnesium sulphate 4 g IV over 20 minutes then 1 g per hour for 24 hours for severe features, betamethasone 12 mg IM twice, 24 hours apart, before 34 weeks; nephrotic range proteinuria: enoxaparin 40 mg subcutaneous daily and furosemide 20 to 80 mg oral daily.
• Procedures: delivery timed by the cause: at 37 weeks for preeclampsia without severe features and immediately after stabilisation for severe features; kidney biopsy only before 28 weeks if needed.
• Special groups: diabetic women need insulin and tight control; women with lupus need hydroxychloroquine 200 mg oral 12-hourly and prednisolone for flares.
• Red flags: blood pressure above 160/110 mmHg, headache, visual disturbance, epigastric pain, seizures, oliguria, platelets below 100 x 10^9/L.
• Follow-up: repeat ratio every 1 to 2 weeks; blood pressure at each visit; review at 6 weeks postpartum, with referral to nephrology for proteinuria persisting beyond 3 months.