Treatment of asymptomatic bacteriuria in pregnancy

Untreated bacteriuria in pregnancy is associated with a 20 to 30% increased risk of developing pyelonephritis in later pregnancy and may be associated with preterm birth and low birth weightAustralian Living Evidence Collaboration, 2024Bonkat, 2024Smaill, 2019The American College of Obstetricians and Gynaecologists (ACOG), 2023. This is likely due to physiological changes to the urinary tract during pregnancy. Antibiotic treatment of asymptomatic bacteriuria in pregnancy reduces the risk of symptomatic urinary tract infection (UTI)Bonkat, 2024The American College of Obstetricians and Gynaecologists (ACOG), 2023Glaser, 2015Kazemier, 2015Nicolle, 2019.

When prescribing for pregnant patients, consider the safety of the antimicrobial in the individual patient.

Treat pregnant patients with confirmed asymptomatic bacteriuria; use susceptibility results to guide therapyGlaser, 2015Nicolle, 2019Smaill, 2019Widmer, 2015. If susceptibility is confirmed, suitable regimens include:

1nitrofurantoin 100 mg orally, 6-hourly for 5 days123. For dosage adjustment in adults with kidney impairment, see nitrofurantoin dosage adjustment nitrofurantoin nitrofurantoin nitrofurantoin

OR

2amoxicillin 500 mg orally, 8-hourly for 5 days. For dosage adjustment in adults with kidney impairment, see amoxicillin dosage adjustment amoxicillin amoxicillin amoxicillin

OR

3cefalexin 500 mg orally, 12-hourly for 5 days. For dosage adjustment in adults with kidney impairment, see cefalexin dosage adjustment cefalexin cefalexin cefalexin

For patients who have had a nonsevere (immediate or delayed) hypersensitivity reaction to a penicillin4, use the nitrofurantoin or cefalexin regimen above if susceptibility is confirmed.

For patients who have had a severe (immediate or delayed)5 hypersensitivity reaction to a penicillin, use the nitrofurantoin regimen above if susceptibility is confirmed.

Confirm the infection has resolved by repeating urine culture 1 to 2 weeks after treatment is completed. If persistent bacteriuria is identified, see Recurrent UTI and bacteriuria in pregnancy.

If Streptococcus agalactiae (group B streptococcus [GBS]) is detected in urine at any stage of pregnancy, intrapartum prophylaxis for GBS is usually indicated – see Prevention of neonatal Streptococcus agalactiae (group B streptococcus) disease.

1 An alternative regimen is 100 mg 12-hourly for 5 days. This is from a study using Macrobid®, a slow-release formulation unavailable in Australia.Return
2 Avoid using nitrofurantoin close to delivery (after 37 weeks gestation, or sooner if early delivery is planned) because of the possible increased risk of neonatal jaundice and haemolytic anaemia.Return
3 Retrospective data suggest that nitrofurantoin is safe and effective for short-term treatment (5 to 7 days) of acute cystitis in patients with a glomerular filtration rate (GFR) of 30 mL/min or moreCunha, 2017Geerts, 2013Santos, 2016Singh, 2015.Return
4 Cefalexin may be used in patients who have had a nonsevere (immediate or delayed) reaction to amoxicillin or ampicillin. However, because cross-reactivity between these drugs is possible, consideration should be given to the extent of the reaction, patient acceptability, and the suitability of non–beta-lactam options.Return
5 Severe immediate hypersensitivity reactions include anaphylaxis, compromised airway, airway angioedema, hypotension and collapse. Severe delayed hypersensitivity reactions include cutaneous adverse drug reactions (eg drug rash with eosinophilia and systemic symptoms [DRESS], Stevens–Johnson syndrome/toxic epidermal necrolysis [SJS/TEN], severe blistering or desquamative rash), and significant internal organ involvement (eg acute interstitial nephritis).Return