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Pregnancy outcomes in women infected with Chlamydia trachomatis: a population-based cohort study in Washington State


Objectives: To measure the risk of preterm delivery, premature rupture of membranes, infant low birth weight and infant mortality, by a population-based retrospective cohort study using Washington State birth certificate data.

Methods: All women diagnosed with Chlamydia trachomatis infection (n = 851), noted with a check box on the birth certificate from 2003, and a randomly selected sample of women not diagnosed with C trachomatis (n = 3404) were identified. To assess the RR between chlamydia infection and pregnancy outcomes, multivariable logistic regression analysis was used.

Results: Women with chlamydia infection were younger, more likely to be non-white and had less years of education compared with women without chlamydia. Additionally, they were more likely to have inadequate prenatal care and coinfections with other sexually transmitted infections. After adjusting for age and education, chlamydia-infected women were at an increased risk of preterm delivery (RR 1.46, 95% CI 1.08 to 1.99) and premature rupture of membranes (RR 1.50, 95% CI 1.03 to 2.17) compared with non-infected women. However, no increased risk of infant death (RR 1.02, 95% CI 0.37 to 2.80) or low birth weight (RR 1.12, 95% CI 0.74 to 1.68) associated with chlamydia infection was observed.

Conclusion: This study suggests that C trachomatis is associated with an increased risk of preterm delivery and premature rupture of membranes, but not with infant death and low birth weight. Routine screening and opportune treatment for C trachomatis should be considered a necessary part of prenatal care to reduce these adverse pregnancy outcomes.

  • STI, sexually transmitted infection

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  • Published Online First 7 March 2007

  • Funding: This study was supported in part by the University of Washington Amauta Health Informatics Research and Training Program, a Fogarty International Center/NIH funded grant (D43TW007551) and the Fogarty/Ellison Fellowship, an NIH training grant (D43TW00007). The sponsor was not involved in any part of the study.

  • Competing interests: None.

  • MMB contributed to the development of the proposal, literature review, data analysis, outline, writing and review of the paper. FAC contributed to the development of the proposal, literature review, data analysis, outline, writing and review of the paper. IEA contributed to the literature review, data analysis, writing and review of the paper. SEH contributed to the outline, writing, review and editing of the paper.

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