Treatment of Asymptomatic Bacteriuria in Pregnancy

Rationale for Treatment

Pregnant women with untreated asymptomatic bacteriuria have a significantly higher risk (20-35%) of developing pyelonephritis compared to those who receive treatment (1-4%) 1, 2
Untreated asymptomatic bacteriuria is associated with increased risk of preterm delivery and low birth weight infants 2, 3
Treatment of asymptomatic bacteriuria reduces the risk of preterm birth from approximately 53 per 1000 to 14 per 1000 2
Antimicrobial therapy reduces the risk of very low birth weight from approximately 137 per 1000 to 88 per 1000 2
The American College of Obstetricians and Gynecologists and other guideline societies recommend screening for and treatment of asymptomatic bacteriuria during pregnancy as a standard of care in developed countries 1

Urine culture should be collected at one of the initial prenatal visits early in pregnancy 2
Asymptomatic bacteriuria occurs in 2-7% of pregnant women 2

For pregnant women with asymptomatic bacteriuria, a 4-7 day course of antimicrobial treatment is recommended 2, 4
Nitrofurantoin is often the preferred antibiotic due to its safety profile in pregnancy and effectiveness against common pathogens 4
Beta-lactam antibiotics such as ampicillin or cephalexin are safe alternatives during pregnancy 4
Single-dose regimens have shown lower rates of bacteriuria clearance compared to short-course regimens and are not recommended 4

The Infectious Diseases Society of America guidelines committee concluded that further evaluation in other populations is necessary before changing the recommendation to screen and treat all pregnant women 2
There is insufficient evidence to recommend for or against repeat screening during pregnancy following an initial negative culture or after treatment of an initial episode 2

After completing antibiotic treatment, a follow-up urine culture is recommended to confirm clearance of the infection 4
Some experts recommend continued screening throughout pregnancy after treatment of bacteriuria 3
Recurrence is common and may require re-treatment 4

The American College of Obstetricians and Gynecologists and the Infectious Diseases Society of America recommend treating each recurrence of asymptomatic bacteriuria with a 4-7 day course of antibiotics, followed by periodic screening with urine cultures throughout the remainder of pregnancy, to prevent progression to pyelonephritis and adverse pregnancy outcomes 5, 6
Antimicrobial therapy is essential to prevent progression to pyelonephritis and adverse pregnancy outcomes in pregnant women with recurrent asymptomatic bacteriuria 7

The Infectious Diseases Society of America guidelines explicitly recommend periodic screening for recurrent bacteriuria should be undertaken following therapy as a Grade A-III recommendation, and continue periodic screening with urine cultures throughout pregnancy after any treated episode 5, 6
Untreated asymptomatic bacteriuria carries a 20-35% risk of pyelonephritis, reduced to 1-4% with treatment, highlighting the importance of aggressive management in pregnant women 7