TOPLINE:

Urinary tract infection (UTI) diagnosed during pregnancy was significantly associated with a higher risk for preterm birth, and the risk was highest within 0-6 days after the diagnosis of UTI and particularly when the infection occurred before 28 weeks of gestation.

METHODOLOGY:

• Researchers conducted an observational study to evaluate how the gestational week at UTI diagnosis and the interval between diagnosis and delivery are associated with the risk for preterm birth.
• They used data from linked registers in Sweden and included 684,595 deliveries between 2014 and 2020.
• The analysis included pregnant women with a first recorded diagnosis of UTI identified using standardised diagnostic codes in the national patient register.
• The outcome was the risk for preterm birth, stratified by gestational week — 22-27, 28-31, and 32-36 weeks.

TAKEAWAY:

• Overall, 19,499 (2.8%) women were diagnosed with UTI during pregnancy. After adjustments, women diagnosed with UTI at 22-27, 28-31, and 32-36 weeks of gestation had an approximately 18-fold, 13-fold, and 6-fold higher risk for preterm birth within 0-6 days of the diagnosis, respectively, than those without UTI.
• At 7-13 days after UTI diagnosis, the risk for preterm birth was still raised, approximately 10-fold, 4-fold, and 3-fold higher among women diagnosed with UTI at 22-27, 28-31, and 32-36 weeks of gestation, respectively, than among those without UTI.
• The elevated risk for preterm birth persisted at least 3 weeks after UTI diagnosis, about 2.5-fold and 3-fold higher at 22-27 and 28-31 weeks of gestation, respectively.
• Women diagnosed with UTI at 22-27, 28-31, and 32-36 weeks of gestation had extreme preterm birth (2.2% vs 0.3%), very preterm birth (2.8% vs 0.5%), and moderate-to-late preterm birth (7.1% vs 2.5%), respectively, compared with those without UTI.

IN PRACTICE:

"Our results highlight the importance of raising awareness of the risk of preterm birth among women and healthcare personnel as well as the importance of carefully adhering to the national guidelines," the authors wrote.

SOURCE:

This study was led by Karin Dahlquist, Helsingborg Hospital, Helsingborg, Sweden. It was published online on February 13, 2026, in Acta Obstetricia et Gynecologica Scandinavica.

LIMITATIONS:

Due to the observational study design, reversed causation and residual confounding could not be ruled out. Primary care data were not captured, so milder UTI may be missed, leading to an underestimation of UTI frequency. Only the first recorded diagnosis of UTI was analysed, which may have limited generalisability.

DISCLOSURES:

This study was funded by the Stig and Ragna Gorthon Foundation for Medical Research. No relevant conflicts of interest were disclosed by the authors.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.