Asymptomatic bacteriuria and uti in pregnancy
Asymptomatic Bacteriuria (ASB) and UTI in Pregnancy Guideline
MAHEC FM-OB Regional Collaborative
ASB is defined as persistent bacterial colonization of the
urinary tract without urinary symptoms; defined by >100,000 CFU of a single organism.
Prevalence is similar to the non-pregnant population (~2 % in higher and up to 10% in
lower socioeconomic groups). UTI/cystitis has symptoms of increased frequency,
urgency, dysuria, hematuria, pyuria, and lack of evidence for systemic illness. The IDSA
recommends accepting a lower CFU of >102 of a single organism if symptomatic. Risk and significance:
No difference between pregnant and non-pregnant populations;
risk factors include: age (1% increase/decade of life), parity, sexual activity, h/o
chlamydia infection, lower socioeconomic status, history of recurrent UTI, DM, sickle
cell disease (renal damage), anatomic or functional GU abnormalities. Pregnant women
with untreated ASB in early pregnancy have a 20-40% risk of developing a symptomatic
urinary tract infection, usually in the form of pyelonephritis, in later pregnancy. Pyelo
increases risk of PTL, low birth weight infants, and fetal mortality. Pyelo places the
patient at increased risk for anemia, thrombocytopenia, transient renal insufficiency,
postpartum endometritis, sepsis, and ARDS. Treatment of ASB has been shown to reduce
subsequent infection by 80-90% and reduce incidence of preterm delivery and low birth
weight infants. Screening (USPSTF and ACOG):
Recommended for all pregnant women
Urine culture by clean catch at initial OB visit (best if 12-16 weeks) identifies
80% of women; urine cultures monthly would catch an additional 1-2% and thus is not routinely recommended. Urinalysis and urine dipstick are not adequate screening for ASB (presence of pyuria, leukocyte esterase, and/or nitrites have high specificities but poor sensitivities and thus poor positive predictive values for ASB). Urine oxoid is acceptable and less expensive (semi-quantitative dip inoculum method). Catheterized urine would catch 96% of ASB but increases complication risk in pregnant women and is only indicated if repeated contaminated clean catch urines are obtained.
Prior guidelines have emphasized that African American patients with UTI in
pregnancy be screened for sickle cell disease; current prenatal screening
recommendations include hemoglobin electrophoresis for this group regardless. Management: See algorithm
Treatment: Medications commonly used (ultimately base choice on sensitivities):
Amoxicillin 3 g in a single dose or 500 mg TID
Cephalexin 2-3 g in a single dose or 250-500 mg QID Ampicillin 2-3 g in a single dose or 250-500 mg QID Nitrofurantoin 100 mg BID (some evidence against use in 1st trimester due to
association with birth defect but these studies were not strong)
Fosfomycin 3 g in a single dose
Trimethoprim/Sulfa 160/800 BID (contraindicated in 1st trimester
teratogenicity and in late 3rd trimester
due to risk of
(Note: Fluoroquinolones and tetracyclines are contraindicated in pregnancy)
No evidence to support one medication over another; most important issue is
Resistance increasing to ampicillin and trimethoprim/sulfa and thus should not be
Optimal length of therapy controversial, most recommend 3-7 days; 7-10 days
GBS bacteriuria implies heavy colonization with GBS, see GBS protocol for
Lactobacilli and diptheroids should be considered vaginal contaminants and not
Treatment and management of pyelonephritis:
Occurs in 1-2 % of pregnant women, most often in the 2nd and 3rd trimesters.
Associated with systemic symptoms including fever, CVA tenderness, flank pain, nausea,
vomiting, shaking chills, leukocytosis, pyuria. Most common finding is fever and CVA
tenderness. Hospitalization is generally considered standard of care, although outpatient
management may be considered in reliable, healthy patients less the 24 weeks EGA with
strict follow up (cover with IM ceftriaxone x 2 doses 24 hrs apart). IV hydration and
parenteral abx are indicated for at least 24 hrs. No specific IV regimen has been shown
to be superior. Common regimens include cefazolin +/-gentamicin, cefuroxime or
ceftriaxone. Renal US is appropriate to further evaluate renal tract in persistent or
Suppressive therapy is indicated in:
1) Patients with a positive screen for ASB and fail to respond to BOTH an initial
course of therapy AND, if the TOC cx is positive, fail to respond to a 7-10 day course of therapy with a different abx depending on sensitivities.
2) Patients with recurrent bacteriuria on surveillance cultures after initial clearing of
3) Patients with 2 symptomatic UTIs 4) Patients with pyelonephritis.
Nitrofurantoin 100 mg q HS; Cephalexin 250 mg qHS; Amoxicillin 250 mg qHS
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Widmer VJ et al. Duration of treatment for asymptomatic bacteriuria during pregnancy. Cochrane Review 2007
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Presence of a Na1-stimulated P-type ATPase in the plasmamembrane of the alkaliphilic halotolerant cyanobacteriumAphanothece halophyticaKanjana Wiangnon1, Wuttinun Raksajit1 & Aran Incharoensakdi1,21Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand; and 2Center for Environmental Stress Tolerance inPlants, Faculty of Science, Chulalongkorn University