Antibiotics for asymptomatic bacteriuria in pregnancy

Smaill FM, Vazquez JC

Published Online:

January 21, 2009

Antibiotics can reduce the risk of kidney infections in pregnant women who have a urine infection but no symptoms of infection.

A urine infection without any of the typical symptoms associated with an acute urine infection (asymptomatic bacteriuria) occurs in 2% to 10% of pregnancies. It may lead to kidney infection (pyelonephritis) in the mother and may possibly contribute to low birthweight babies and preterm birth (before 38 weeks). The review of trials on antibiotic treatment for these women with no symptoms but high bacterial counts in their urine found 14 studies involving 2302 women. Most of the trials were of poor quality. Antibiotics were effective in clearing asymptomatic bacteriuria and reducing the incidence of symptomatic kidney infection in the mother. The incidence of low birthweight seemed also to be reduced. None of the studies adequately assessed adverse effects of treatment. More research is needed.

Abstract (click to read)

Background:

Asymptomatic bacteriuria occurs in 2% to 10% of pregnancies and, if not treated, up to 30% of mothers will develop acute pyelonephritis. Asymptomatic bacteriuria has been associated with low birthweight and preterm delivery.

Objectives:

To assess the effect of antibiotic treatment for asymptomatic bacteriuria on persistent bacteriuria during pregnancy, the development of pyelonephritis and the risk of low birthweight and preterm delivery.

Search strategy:

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2007).

Selection criteria:

Randomized trials comparing antibiotic treatment with placebo or no treatment in pregnant women with asymptomatic bacteriuria found on antenatal screening.

Data collection and analysis:

We assessed trial quality.

Main results:

Fourteen studies were included. Overall the study quality was poor. Antibiotic treatment compared to placebo or no treatment was effective in clearing asymptomatic bacteriuria (risk ratio (RR) 0.25, 95% confidence interval (CI) 0.14 to 0.48). The incidence of pyelonephritis was reduced (RR 0.23, 95% CI 0.13 to 0.41). Antibiotic treatment was also associated with a reduction in the incidence of low birthweight babies (RR 0.66, 95% CI 0.49 to 0.89) but a difference in preterm delivery was not seen.

Authors' conclusions:

Antibiotic treatment is effective in reducing the risk of pyelonephritis in pregnancy. A reduction in low birthweight is consistent with current theories about the role of infection in adverse pregnancy outcomes, but this association should be interpreted with caution given the poor quality of the included studies.

This record should be cited as:

Smaill FM, Vazquez JC. Antibiotics for asymptomatic bacteriuria in pregnancy. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: CD000490. DOI: 10.1002/14651858.CD000490.pub2

Assessed as up to date:

January 31, 2007

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Primary Review Group:

Pregnancy and Childbirth Group

Health topics:

Infectious disease > Urinary tract infections > Treatment: asymptomatic infection

Kidney disease > Urinary tract infections > Treatment: asymptomatic infection

Pregnancy & childbirth > Infection during pregnancy > Urinary tract infections

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Antibiotics for asymptomatic bacteriuria in pregnancy

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