Asymptomatic bacteriuria is the presence of bacteria in the urine without symptoms of a urinary tract infection.  It can occur in 2 to 15% of pregnant women and if left untreated, some can develop a serious kidney infection called acute pyelonephritis.  

Screening For Asymptomatic Bacteriuria

The current recommendation is to screen for asymptomatic bacteriuria in pregnant women during their first trimester, or at their first prenatal visit if that occurs later.  This is also the same recommendations as the Infectious Disease Society of America (IDSA). For non pregnant women it is not recommended to screen for or treat asymptomatic bacteriuria.

Screening is done by collecting a urine sample and having a laboratory analyze the urine for bacteria with a culture and sensitivity.  A positive result would be greater than 100×10^6 CFU/L of a specific bacteria without specific symptoms for a urinary tract infection.   

Rationale For Screening And Treatment

There is a correlation between asymptomatic bacteriuria and adverse pregnancy outcomes.  

Untreated bacteriuria can be associated with preterm birth, low birth weight, and perinatal mortality.  The risk may be reduced if bacteriuria is eradicated. Some women who are not at increased risk of urinary tract infections in pregnancy (no history of UTIs, diabetes, or kidney problems) and are more concerned with potential risks of antibiotics may choose not to be screened for asymptomatic bacteriuria.

Management of Asymptomatic Bacteriuria

Once the culture and sensitivities are back from the laboratory, an appropriate antibiotic is chosen to eradicate the bacteria present in the urine.  

Antibiotics are chosen based on the sensitivity report as well as safety for use during pregnancy, as well as the trimester of the pregnancy.  

The duration of therapy depends on the organism present in the urine as well as the antibiotic chosen. 

It is recommended that another urine culture is done one week after completion of treatment to ensure eradication.   

This post was co-authored by Erin Manchuk, BScPharm, BCGP and Stephanie Liu, MD, MSc, CCFP, BHSc.