Meta-analysis of the relationship between asymptomatic bacteriuria and preterm delivery/low birth weight

Roberto Romero, Enrique Oyarzun, Moshe Mazor, Marina Sirtori, John C. Hobbins, Michael Bracken

Research output: Contribution to journalArticlepeer-review

360 Scopus citations


The relationship between asymptomatic bacteriuria and prematurity/low birth weight (LBW) is still a controversial issue, despite many studies. Meta-analysis, a research tool designed to analyze and combine the results of previous studies, may resolve this discrepancy among contradictory results of clinical trials. The purpose of this study was to examine the relationship between asymptomatic bacteriuria and preterm delivery/LBW using meta-analysis. Reports from the literature were classified according to study design into cohort or domized-treatment control trials. Meta-analysis of cohort studies showed that untreated asymptomatic bacteriuria during pregnancy significantly increased rates of LBW and preterm delivery. Nonbacteriuric patients had only about two-thirds the risk (typical relative risk=0.65; 95% confidence interval 0.57, 0.74) of LBW and half the risk (typical relative risk=0.50; 95% confidence interval 0.36, 0.70) of preterm delivery of those with untreated asymptomatic bacteriuria. These reduced risks correspond to a 3.4 (confidence interval 1.8, 5.0) percentage-point difference in LBW and a 3.8 (1.1, 6.4) percentage-point difference in preterm delivery. The analysis of randomized clinical trials showed that antibiotic treatment significantly reduced the risk of LBW (typical relative risk=0.56; 95% confidence interval 0.43, 0.73), with a substantial reduction of 6.4 (confidence interval 3.3, 9.5) percentage points in the rate of LBW. We conclude that clinical and epidemiologic evidence indicates a strong association between untreated asymptomatic bacteriuria and LBW/preterm delivery and that antibiotic treatment is effective in reducing the occurrence of LBW.

Original languageEnglish
Pages (from-to)576-582
Number of pages7
JournalObstetrics and Gynecology
Issue number4
StatePublished - 1 Jan 1989
Externally publishedYes

ASJC Scopus subject areas

  • Obstetrics and Gynecology


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