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Asymptomatic bacteriuria in pregnancy — MSRA MCQ

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HardUrinary Tract InfectionsAsymptomatic bacteriuria in pregnancyMSRA

A 30-year-old woman who is 38+4 weeks pregnant is reviewed after a midstream urine culture, sent because of a previous UTI in pregnancy, grows >10⁵ CFU/mL Escherichia coli. She has no dysuria, frequency, urgency, suprapubic pain, fever, rigors, loin pain, vomiting or vaginal symptoms. She is well, observations are normal, and eGFR is 82 mL/minute/1.73 m². The isolate is susceptible to nitrofurantoin and cefalexin, and resistant to amoxicillin and trimethoprim. She has no drug allergies or G6PD deficiency. Induction of labour is planned in 3 days. What is the most appropriate management?

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Correct answer: C — Prescribe cefalexin 500 mg orally twice daily for 7 days

This is asymptomatic bacteriuria: significant bacteriuria in the absence of urinary symptoms. Unlike in non-pregnant adults, it requires immediate antibiotic treatment in pregnancy because of the increased risk of pyelonephritis and adverse pregnancy outcomes. Treatment should be guided by susceptibility results and given for 7 days. Cefalexin is therefore the best option: the organism is susceptible, and NICE includes cefalexin as an option for asymptomatic bacteriuria in pregnancy. Nitrofurantoin would ordinarily be suitable for a susceptible lower urinary isolate with adequate renal function, but NICE advises avoiding it at term because of the risk of neonatal haemolysis; she is already 38+4 weeks and due for induction shortly. Amoxicillin is inappropriate because the isolate is resistant. Withholding treatment wrongly applies the approach to asymptomatic bacteriuria in non-pregnant adults. Pivmecillinam is a treatment option for uncomplicated lower UTI in non-pregnant women, but is not a NICE-listed regimen for asymptomatic bacteriuria in pregnancy and the proposed 3-day course is inadequate in this context.

Reference: Urinary tract infection (lower): antimicrobial prescribing — Recommendations (31 October 2018) — https://www.nice.org.uk/guidance/ng109/chapter/Recommendations Urinary tract infection (lower): antimicrobial prescribing — Summary of the evidence (31 October 2018) — https://www.nice.org.uk/guidance/ng109/chapter/summary-of-the-evidence Nitrofurantoin 100 mg Tablets — Summary of Product Characteristics (2026) — https://www.medicines.org.uk/emc/product/14473/smpc