Urinary tract infections in pregnancy

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What this article covers

• Overview

  Pregnancy is a risk factor for urinary tract infection and also converts asymptomatic bacteriuria from a condition that does not require treatment into one that does, because untreated bacteriuria in pregnancy carries obstetric risk.

• Epidemiology

  Pregnancy is a recognized risk factor for urinary tract infection (UTI), alongside sexual activity, structural or functional urinary tract abnormalities, spermicide and diaphragm use, diabetes, and a prior UTI history.

• Risk factors

  Pregnancy itself, through progesterone-mediated ureteral smooth muscle relaxation and mechanical compression of the ureters by the gravid uterus, promoting urinary stasis.

• Pathophysiology

  Progesterone relaxes ureteral and bladder smooth muscle, and the enlarging uterus mechanically compresses the ureters (more often the right), producing physiologic hydroureter and hydronephrosis of…

• Clinical features

  Asymptomatic bacteriuria, by definition, produces no urinary symptoms, which is why it is detected only through universal screening rather than by presentation, and remains the presentation of most bacteriuria identified in pregnancy.

• Differential diagnosis

  Preterm labor without infection: uterine contractions and cervical change without fever, flank pain, or a positive urine culture, distinguished by a negative urinalysis and culture.

• Diagnosis

  The diagnosis of asymptomatic bacteriuria in pregnancy is established by a positive urine culture of at least 10^5 colony-forming units per milliliter of a single bacterial species on two consecutive…

• Management

  First, for asymptomatic bacteriuria or acute cystitis in pregnancy, start an oral pregnancy-safe agent: amoxicillin-clavulanate 875 mg/125 mg PO every 12 hours for 5-7 days, safe throughout pregnancy.

• Complications

  Pyelonephritis, the principal complication of untreated asymptomatic bacteriuria or cystitis in pregnancy, and itself a driver of further maternal and fetal risk.

• Prognosis

  Screened and treated asymptomatic bacteriuria in pregnancy substantially lowers the risk of progression to pyelonephritis, which is the rationale for universal screening rather than symptom-triggered testing.

• Prevention

  Screen every pregnant woman with a urine culture at the first prenatal visit or by 12-16 weeks gestation, regardless of symptoms, and treat any culture showing at least 10^5 CFU/mL of a single organism.