Treatment of E. coli Infections During Pregnancy
Ampicillin should not be used for E. coli infections during pregnancy due to high resistance rates. The recommended first-line treatments are nitrofurantoin or cephalexin for urinary tract infections caused by E. coli in pregnant women. 1
First-Line Treatment Options for E. coli UTIs in Pregnancy
For urinary tract infections (UTIs) caused by E. coli during pregnancy, the following treatments are recommended:
Nitrofurantoin - 100 mg twice daily for 5-7 days
- Safe and effective during pregnancy
- High strength of evidence for efficacy 1
- Should be avoided in the third trimester due to risk of hemolytic anemia in G6PD-deficient infants
Cephalexin - 500 mg four times daily for 5-7 days
- Safe beta-lactam antibiotic with long history of use in pregnancy
- Moderate strength of evidence 1
Amoxicillin-clavulanate - 500/125 mg twice daily for 3-7 days
- Alternative when resistance to first-line agents is suspected
- Moderate strength of evidence 1
Treatment Algorithm Based on Clinical Presentation
Asymptomatic Bacteriuria
- Screen all pregnant women for asymptomatic bacteriuria
- Treat with nitrofurantoin or cephalexin as first-line options 1, 2
- Follow-up urine culture recommended after treatment to confirm eradication
Uncomplicated Cystitis
- Nitrofurantoin 100 mg twice daily for 5 days
- Cephalexin 500 mg four times daily for 5-7 days
- Obtain urine culture before starting antibiotics 1
Pyelonephritis
- Hospitalization and IV antibiotics initially
- Second or third-generation cephalosporins are recommended 2
- Switch to oral antibiotics after clinical improvement
- Complete 10-14 days of total therapy
Special Considerations
Antibiotic Resistance
- E. coli resistance to ampicillin is high, making it an inappropriate choice 2
- Obtain urine culture before starting antibiotics to guide therapy
- Consider local resistance patterns when selecting empiric therapy
Timing During Pregnancy
- Trimethoprim-sulfamethoxazole should be avoided in the first trimester due to risk of neural tube defects and in the third trimester due to risk of kernicterus 1
- Fluoroquinolones are contraindicated during pregnancy 3
- Tetracyclines are contraindicated during pregnancy 1
Prevention of Recurrence
- Increased fluid intake
- Postcoital prophylaxis with nitrofurantoin or cephalexin for women with history of recurrent UTIs 1
- Maintain good urogenital hygiene
Follow-up Recommendations
- Obtain test of cure urine culture 1-2 weeks after completing treatment
- Re-screening later in pregnancy is recommended for women with prior UTIs
- Treat any recurrences promptly to prevent complications
Risks of Untreated E. coli Infections
- Increased risk of pyelonephritis (20-30% of untreated bacteriuria cases) 4
- Increased risk of preterm labor and low birth weight 2
- Potential for maternal sepsis if severe infection goes untreated
E. coli is the most common pathogen in urinary tract infections during pregnancy 2. Proper treatment is essential to prevent complications that could affect both mother and fetus. The choice of antibiotic should balance efficacy against the organism with safety for the developing fetus.