Urinary Tract Infection in Pregnancy

Urinary tract infection in pregnancy is infection anywhere in the urinary tract, including asymptomatic bacteriuria, cystitis and pyelonephritis, most often with Escherichia coli. Pregnancy lengthens the ureters and slows urine flow, so untreated bacteriuria often progresses to pyelonephritis. It causes preterm birth, low birth weight and sepsis, and is one of the commonest reasons for antenatal admission.

• Risk factors: diabetes, sickle cell disease, previous infection, renal tract anomaly, stones, HIV, poor hygiene.
• About 2 to 10 percent of pregnant women have bacteriuria.
• Screening and treatment prevents pyelonephritis.

Features range from none to dysuria, frequency, urgency and suprapubic pain (cystitis), to fever, loin pain, rigors and vomiting (pyelonephritis). Examine temperature, loin tenderness, suprapubic tenderness and uterine contractions.

• Fever above 38 degrees Celsius with loin pain suggests pyelonephritis.
• Preterm contractions may occur.
• Differential diagnosis: vaginitis, sexually transmitted infection, labour, appendicitis, kidney stones, chorioamnionitis, malaria.
• Complications: pyelonephritis, sepsis, preterm labour, low birth weight, acute kidney injury, respiratory distress syndrome, maternal death.

The approach is urine culture, with dipstick and microscopy for rapid assessment.

• Mid stream urine culture before antibiotics: growth of 10^5 colony forming units/mL (10^3 with symptoms) confirms infection.
• Dipstick for nitrites and leucocyte esterase; microscopy for pus cells.
• Full blood count, creatinine, blood cultures and renal ultrasound for pyelonephritis.
• Test of cure culture 1 to 2 weeks after treatment.

The principle is treatment based on the type and culture result, test of cure and prophylaxis for recurrence.

• Supportive: oral fluids 2 to 3 litres daily; frequent voiding; wipe front to back; paracetamol for fever; admit for pyelonephritis.
• Pharmacological: asymptomatic bacteriuria or cystitis: cefalexin 500 mg oral 6-hourly for 7 days, or nitrofurantoin 100 mg modified release oral 12-hourly for 5 days (avoid in the first trimester when alternatives exist, at term and in glucose-6-phosphate dehydrogenase deficiency), or amoxicillin 500 mg oral 8-hourly for 7 days if sensitive, or fosfomycin 3 g oral single dose; pyelonephritis: ceftriaxone 1 to 2 g IV 24-hourly until afebrile for 24 to 48 hours, then cefalexin 500 mg oral 6-hourly to complete 10 to 14 days; prophylaxis after two infections: cefalexin 250 mg or nitrofurantoin 50 mg oral at night until 6 weeks postpartum; avoid trimethoprim in the first trimester, tetracyclines and fluoroquinolones.
• Procedures: ureteric stent or nephrostomy for obstruction with infection.
• Special groups: group B streptococcus in urine at any count is treated and also requires intrapartum benzylpenicillin 5 g IV then 2.5 g 4-hourly until delivery; renal impairment avoids gentamicin and nitrofurantoin; penicillin allergy uses ceftriaxone if the reaction was not severe.
• Red flags: fever above 38 degrees Celsius, rigors, loin pain, vomiting, hypotension, contractions, oliguria.
• Follow-up: culture 1 to 2 weeks after treatment and monthly to delivery; renal ultrasound after pyelonephritis; review at 6 weeks postpartum.