Urinary Tract Infections & Asymptomatic Bacteriuria in Pregnancy

Fifty vocabulary flashcards summarizing key concepts, definitions, organisms, diagnostics, management strategies, and antibiotic safety for urinary tract infections and asymptomatic bacteriuria in pregnancy.

Urinary Tract Infection (UTI)

Infection of any part of the urinary system; in pregnancy classified as lower-tract (acute cystitis) or upper-tract (acute pyelonephritis).

Lower Tract Infection (Acute Cystitis)

Symptomatic bladder infection presenting with dysuria, urgency, and frequency without systemic signs.

Upper Tract Infection (Acute Pyelonephritis)

Infection of the kidney and renal pelvis, usually with fever, flank pain, nausea, or costovertebral tenderness.

Asymptomatic Bacteriuria

Significant bacterial growth in urine culture (≥10^5 CFU/mL) without UTI symptoms during pregnancy.

Incidence of Asymptomatic Bacteriuria in Pregnancy

Occurs in roughly 2–7 % of pregnant women, most often detected early in gestation.

Major Risk Factors for Bacteriuria in Pregnancy

History of prior UTI, pre-existing diabetes mellitus, and low socioeconomic status.

Recurrent Bacteriuria

Repeat episodes of bacteriuria during pregnancy; more common than in nonpregnant women due to physiologic changes.

Screening Recommendation (IDSA) for Pregnancy

All pregnant women should have at least one urine culture to screen for asymptomatic bacteriuria early in pregnancy.

Optimal Screening Timing

First prenatal visit, typically 12–16 weeks’ gestation, with a midstream urine culture.

Midstream Urine Collection

Patient discards initial urine stream, then collects the mid-portion to reduce contamination.

Clean-Catch Technique

Local cleansing of the urethral area before voiding; studies show it adds little benefit over midstream collection alone.

Diagnostic Threshold for Asymptomatic Bacteriuria

≥10^5 CFU/mL of the same organism in one voided specimen (or two consecutive) without symptoms; ≥10^2 CFU/mL from catheter sample.

Colony-Forming Unit (CFU)

Measure of viable bacterial numbers; used to quantify bacteriuria on urine culture.

Typical Uropathogen in Pregnancy

Escherichia coli, accounting for about 70 % of infections; others include Klebsiella, Proteus, and Group B Streptococcus.

Extended-Spectrum β-Lactamase (ESBL)

Enzyme conferring resistance to many β-lactam antibiotics; ESBL-producing strains are an emerging concern in pregnancy.

Physiologic Changes Predisposing to Pyelonephritis

Smooth-muscle relaxation and ureteral dilation in pregnancy allow easier bacterial ascent from bladder to kidney.

Pregnancy Immunosuppression Effect

Reduced mucosal IL-6 and antibody responses to E. coli, facilitating progression from bacteriuria to infection.

Untreated Bacteriuria Pregnancy Outcomes

Linked to higher rates of pyelonephritis, preterm birth, low birth weight, and perinatal mortality.

Preterm Birth Association

Meta-analysis shows asymptomatic bacteriuria doubles the risk of delivering before 37 weeks.

Low Birth Weight Association

Infants of mothers with untreated bacteriuria have about 1.5-fold increased risk of <2500 g birth weight.

Rationale for Treating Asymptomatic Bacteriuria

Antibiotics lower pyelonephritis risk by 70–80 % and improve pregnancy outcomes.

Preferred Antibiotic Classes in Pregnancy

β-lactams, nitrofurantoin, and fosfomycin because of favorable safety profiles.

Nitrofurantoin Use Considerations

Generally avoided in the 1st trimester but acceptable when no safer alternatives are available.

Fosfomycin Single-Dose Therapy

3-g oral dose effectively eradicates bacteriuria and is convenient for pregnant patients.

Short-Course Antibiotic Duration

5–7 days (single dose for fosfomycin) is usually adequate, limiting fetal drug exposure.

Follow-Up Culture Controversy

Evidence is insufficient to support routine post-treatment cultures after asymptomatic bacteriuria or cystitis.

Typical Symptoms of Acute Cystitis

Sudden dysuria, urinary urgency, and frequency without systemic signs such as fever.

Pyuria

Presence of leukocytes in urine; usually accompanies symptomatic UTI and its absence suggests alternate diagnoses.

Threshold for Significant Bacteriuria in Symptomatic Women

≥10^2–10^3 CFU/mL of coliforms may indicate true infection when cystitis symptoms are present.

Differential Diagnosis of Dysuria in Pregnancy

Includes vaginitis, urethritis (STIs), and physiologic urinary frequency; confirmed by lack of bacteriuria.

Empiric Antibiotic Choices for Cystitis

Cefpodoxime, amoxicillin-clavulanate, or fosfomycin; nitrofurantoin or TMP-SMX if others unsuitable.

Duration of Therapy for Acute Cystitis

Single dose (fosfomycin) or 3–7 days with other agents, assuming no signs of pyelonephritis.

Recurrent Cystitis Prophylaxis Options

Low-dose nightly or postcoital nitrofurantoin (50-100 mg) or cephalexin (250-500 mg) during pregnancy.

Typical Symptoms of Acute Pyelonephritis

Fever >38 °C, flank pain, nausea/vomiting, and costovertebral angle tenderness; cystitis symptoms may be absent.

Maternal Complications of Pyelonephritis

Can include anemia, sepsis, respiratory distress/ARDS, and renal dysfunction.

Hospitalization Policy for Pyelonephritis

Standard care involves inpatient IV antibiotics until afebrile ≥24–48 h due to high complication risk.

Preferred Empiric IV Antibiotics for Pyelonephritis

Third-generation cephalosporin (e.g., ceftriaxone) or piperacillin-tazobactam depending on local resistance.

Carbapenem Selection in Pregnancy

Meropenem or ertapenem are preferred over imipenem when ESBL organisms are suspected.

Transition to Oral Therapy Criteria

Patient afebrile for 48 h with clinical improvement; switch to oral β-lactam or 2nd-trimester TMP-SMX to complete 7–10 days.

Preventive Antibiotics after Pyelonephritis

Nightly nitrofurantoin or cephalexin for the remainder of pregnancy to reduce recurrence risk.

Postcoital Prophylaxis

Single dose of cephalexin 250 mg or nitrofurantoin 50 mg taken after intercourse for women with intercourse-related UTIs.

Antibiotics Generally Safe in Pregnancy

Penicillins, β-lactamase inhibitor combos, cephalosporins, aztreonam, fosfomycin, and selected carbapenems.

Drugs Usually Avoided in First Trimester

Nitrofurantoin and trimethoprim-sulfamethoxazole due to possible congenital anomaly associations.

Fluoroquinolone Use in Pregnancy

Generally contraindicated; potential fetal cartilage toxicity outweighs benefits.

Aminoglycoside Fetal Risk

Prolonged exposure linked to ototoxicity; reserved only when no safer options exist.

Role of Blood Cultures in Pyelonephritis

Recommended only if sepsis signs or serious comorbidities; routine cultures rarely alter management.

Renal Ultrasound Indications

Severe illness, renal colic, stones, diabetes, prior urologic surgery, or persistent fever to assess for obstruction/abscess.

Tocolysis Considerations with Pyelonephritis

May be used for preterm labor <34 weeks if mother not septic; risk of pulmonary edema must be weighed.

Screening Repetition in Low-Risk Women

Routine re-screening after an initial negative culture is not recommended for low-risk pregnancies.

Rapid Screening Tests vs Culture

Dipsticks and enzymatic strips lack sensitivity/specificity; urine culture remains the gold standard for bacteriuria detection.