SUMMARY:   

Urinary tract infections (UTIs) are one of the most common infections in pregnancy, occurring in about 8% of all pregnancies and range from asymptomatic bacteriuria to acute pyelonephritis. They are associated with adverse pregnancy outcomes such as preterm birth and low birth weight, therefore the timely identification and treatment of these is essential. Anatomic changes during pregnancy increase the risk for UTIs, such as ureteral dilation, the mechanical compression of ureters by the uterus causing urinary stasis, contributing to bacteria colonization and ascending infection. E coli remains the most common identified pathogen. Given the high rates of antibiotic resistance to this organism, the selection of first line therapy must avoid antibiotics such as  amoxicillin and ampicillin. Treatment of symptomatic bacteriuria decreases the risk of pyelonephritis, which can cause significant maternal complications such as DIC and ARDS, as well as fetal complications such as preterm birth. Patients with hemoglobinopathy have higher rates of cystitis and asymptomatic bacteriuria. ACOG provides recommendations regarding urinary tract infection in pregnancy.

Recommendations  

Asymptomatic Bacteriuria (ASB) 

• Screen once early in pregnancy  
• If culture ≥100,000 CFU/mL treatment should be started with antiobiotics adjusted once culture results are available if necessary 
  • Cephalexin: 250 to 500 mgs q6hr po 5 to 7 days  
  • Fosfomycin: 3 g po once  
  • Amoxicillin: 500 mg po q8hr for 5 to 7 days | 875 mg po q12hr for 5 to 7 days | Avoid starting prior to culture results due to high resistance  
  • Amoxicillin-clavulanate: 500 mg po q8hr for 5 to 7 days | 875 mg po q12hr for 5 to 7 days | Avoid starting prior to culture results due to high resistance 
  • ‘Reasonable to offer’ if no other alternatives available  
    • Nitrofurantoin: 100 mgs q12hr po 5 to 7 days 
    • Sulfamethoxazole-trimethoprim: 800/160 mgs q12hrs po 5o to 7 days 
  • Insufficient evidence for repeat screening following treatment  
• Presence of Group B strep 
  • Treat if ≥100,000 CFU/mL 
  • If <100,000 CFU/mL do not treat but it is an indication for group B streptococcus prophylaxis at the time of delivery 

Note: Low risk for anaphylaxis, cephalosporin treatment is appropriate | High risk for anaphylaxis should be treated with alternative regimen  

Acute Cystitis 

• Initiate treatment for symptomatic relief based on the following  
  • Clinical signs: Dysuria | Hematuria | Frequency | Nocturia  
  • Urinalysis: Consistent with UTI 
• Confirmed by urine culture of ≥100,000 organisms  
• Treatment regimen is the same as ASB  (see above) 
  • If symptoms persist  
    • Repeat cultures  
    • Consider daily prophylaxis preferably single daily dose if recurrent infection (≥2 UTIs during pregnancy)  

Pyelonephritis 

• Signs and symptoms  
  • Fever ≥38° degrees C | Nausea and vomiting  
  • Flank pain | CVA tenderness | Renal ultrasonography abnormalities  
  • CBC: Leukocytosis | Bandemia | thrombocytopenia | Anemia  
  • Abnormal urinalysis  
  • May present with preterm labor or severe sequelae (e.g., sepsis)  

Note: Remain suspicious even if only some of the above is present (e.g., fever and UTI)  

• Inpatient treatment recommended for fluid hydration and empiric antibiotics   
• Start parenteral antibiotics prior to culture report  
  • Ampicillin 2g IV q6hr and gentamycin 1.5 mg/kg q8hr or 5 mg/kg IV q24hr 
  • Ceftriaxone 1g IV q24hr 
  • Aztreonam (can be used with beta-lactam allergy) 1g IV q8 to 12hr  
  • Cefepime 1g IV q12hr 

• Adjust antibiotics as needed after urine culture results are available    
• 14 day total course of therapy 
• Follow up suppressive therapy may be considered  

KEY POINTS:   

• Asymptomatic bacteriuria 
  • Screen as early as possible 
  • No evidence for repeating screening during pregnancy, including diabetes or spinal cord injury  
  • Routine dipsticks are not clinically useful and do not detect ASB 
  • A midstream urine culture is recommended 
    • Clean catch specimens do not decrease perineal contamination 
  • Do not treat normal vulvovaginal flora such as
    • Lactobacilli | Corynebacteria species | Coagulase-negative Staphylococcus 
• Cystitis
  • Leukocyte esterase or pyuria has a 97% sensitivity but not specific, due to white cells normally found in vagina/vulva 
  • Nitrates are 94 to 98% specific, but not all bacteria produce nitrates 
  • Use of antibiotics should be guided by sensitivities and safety profiles 
  • Nitrofurantoin is a reasonable first line treatment choice 
    • Patients with known G6PD deficiency should avoid this antibiotic  
  • Recurrent UTIs occur in 4% to 5% of pregnancies and suppressive regimens include 
    • Nitrofurantoin: 100 mg daily  
    • Cephalexin 250 to 500 mg daily  
• Pyelonephritis 
  • Can cause preterm labor, labor, ARDS, sepsis, acute renal insufficiency 
  • Differential diagnosis includes  
    • Nephrolithiasis 
    • Chorioamnionitis 
    • Renal abscess 
    • Urosepsis without pyelonephritis 
  • Blood cultures may not be clinically useful 
  • Majority of patients have clinical improvement in 48 to 72 hours 
  • Recurrent pyelonephritis occurs in 25% of patients before delivery 
  • Consideration of a daily suppressive therapy is the same as for cystitis 

Primary Sources – Learn More  

ACOG Clinical Consensus 4: Urinary Tract Infections in Pregnant Individuals 

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