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Acute lower urinary tract infection in early pregnancy — MSRA MCQ

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HardUrinary Tract InfectionsAcute lower urinary tract infection in early pregnancyMSRA

A 30-year-old woman who is 10+4 weeks pregnant presents with 2 days of dysuria, urinary frequency and suprapubic discomfort. She has no vaginal discharge, fever, rigors, loin pain, vomiting or visible haematuria. She is haemodynamically stable and able to take oral medication. A midstream urine sample sent yesterday has grown >10^5 CFU/mL Escherichia coli. The isolate is susceptible to amoxicillin, cefalexin, nitrofurantoin and trimethoprim. She has no drug allergies, her eGFR is 88 mL/minute/1.73 m², and she has confirmed G6PD deficiency. What is the most appropriate immediate antimicrobial prescription?

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Correct answer: B — Amoxicillin 500 mg three times daily for 7 days

This is symptomatic lower UTI in pregnancy, so she requires immediate antibiotic treatment and the available culture result should guide selection. Nitrofurantoin would usually be first choice in pregnancy when renal function is adequate, but it is contraindicated in G6PD deficiency because of haemolysis risk. Trimethoprim should be avoided in the first trimester because it is a folate antagonist and carries teratogenic risk; adding folic acid does not make it the preferred option when suitable alternatives are available. Amoxicillin is appropriate because the organism is confirmed susceptible. NICE specifies that amoxicillin should be used for pregnant women only when culture results are available and demonstrate susceptibility. It is also a narrower-spectrum option than cefalexin, consistent with antimicrobial stewardship. Cefalexin is a reasonable alternative where amoxicillin is unsuitable, but there is no such limitation here. Fosfomycin is not listed by NICE as a routine treatment option for lower UTI in pregnancy. There are no features of pyelonephritis requiring an upper-UTI regimen or hospital assessment.

Reference: Urinary tract infection (lower): antimicrobial prescribing (NG109) — Recommendations (2018; checked 16 August 2026) — https://www.nice.org.uk/guidance/ng109/chapter/Recommendations Urinary tract infection (lower): antimicrobial prescribing (NG109) — Summary of the evidence (2018; checked 16 August 2026) — https://www.nice.org.uk/guidance/ng109/chapter/summary-of-the-evidence Nitrofurantoin 100 mg Capsules — Summary of Product Characteristics (2025; checked 16 August 2026) — https://www.medicines.org.uk/emc/product/428/smpc