Chronic Kidney Disease in Pregnancy

Chronic kidney disease in pregnancy is reduced kidney function (estimated glomerular filtration rate below 60 mL/minute/1.73 m2 or persistent proteinuria) in a pregnant woman. Causes include glomerulonephritis, diabetic nephropathy, hypertension, lupus nephritis, reflux nephropathy, polycystic kidneys and HIV associated nephropathy. Fertility and pregnancy outcomes worsen with the stage, and pregnancy can accelerate kidney decline.

• Stages by filtration rate: stage 1 is 90 or above, 2 is 60 to 89, 3 is 30 to 59, 4 is 15 to 29, 5 is below 15 mL/minute/1.73 m2.
• Serum creatinine below 125 micromol/L carries good outcomes.
• Risk of preeclampsia, preterm birth and growth restriction rises steeply from stage 3.

Women are often asymptomatic, or have hypertension, oedema, foamy urine, tiredness and anaemia. Look for blood pressure, oedema, fundal height and signs of uraemia in advanced disease.

• Creatinine above 90 micromol/L in pregnancy is abnormal (normal pregnancy range 40 to 75 micromol/L).
• Hypertension is common.
• Differential diagnosis: preeclampsia, acute kidney injury, pyelonephritis, lupus nephritis, normal pregnancy rise in filtration, obstructive uropathy.
• Complications: preeclampsia, accelerated loss of kidney function, preterm birth, growth restriction, stillbirth, anaemia, infection, hypertensive crisis.

The approach is baseline kidney tests with assessment of cause and fetal growth.

• Creatinine, urea, electrolytes, estimated glomerular filtration rate, urine protein to creatinine ratio, urinalysis with microscopy, urine culture.
• Full blood count, ferritin, calcium, phosphate, parathyroid hormone, bicarbonate, HbA1c.
• Renal ultrasound; autoantibodies, complement, hepatitis B and C and HIV tests for cause.
• Uterine artery Doppler at 20 to 24 weeks; growth scans every 4 weeks from 24 weeks.

The principle is blood pressure control, aspirin, infection prevention and timed delivery, with dialysis intensified in advanced disease.

• Supportive: fluids; low salt diet; stop smoking; avoid NSAIDs and nephrotoxins; monthly urine culture; target blood pressure 135/85 mmHg or lower.
• Pharmacological: aspirin 150 mg oral at night from 12 weeks to 36 weeks; calcium carbonate 1 g oral daily; 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) or methyldopa 250 to 500 mg oral 8-hourly (maximum 3 g daily); stop ACE inhibitors, angiotensin receptor blockers, statins and spironolactone before conception; ferrous sulphate 200 mg oral 8-hourly; epoetin alfa 50 to 100 units/kg subcutaneous 3 times weekly for haemoglobin below 10 g/dL after iron repletion; enoxaparin 40 mg subcutaneous daily for nephrotic syndrome with albumin below 25 g/L (20 mg daily if creatinine clearance is below 30 mL/minute); cefalexin 250 mg oral at night for recurrent urinary infection; sodium bicarbonate 500 mg to 1 g oral 8-hourly for acidosis.
• Procedures: dialysis 5 to 6 days weekly (at least 20 hours weekly) to keep pre-dialysis urea below 15 mmol/L for stage 5 disease or rapidly rising creatinine; kidney biopsy only before 28 weeks if cause is unclear and treatment would change; delivery at 37 weeks, earlier for preeclampsia, deterioration or growth restriction.
• Special groups: transplant recipients continue tacrolimus, azathioprine and prednisolone at doses guided by drug levels and stop mycophenolate and sirolimus; women with HIV avoid tenofovir disoproxil if creatinine clearance is below 50 mL/minute and need specialist advice on the regimen; breastfeeding is compatible with most of these drugs except mycophenolate.
• Red flags: blood pressure above 160/110 mmHg, rising creatinine, oliguria, headache, visual change, reduced fetal movements, fever, loin pain.
• Follow-up: antenatal review every 2 weeks, weekly from 32 weeks; creatinine and urine protein at each visit; review at 6 weeks postpartum with kidney function.