Value of routine urine culture in the assessment of preterm labor

To assess the utility and expense of routine urine culture in women evaluated for preterm labor.

A retrospective study of 1,429 patients evaluated for preterm labor over a calendar year. Patients evaluated for preterm labor were identified using the hospital's admissions database and then cross-referenced with the hospital microbiology laboratory's database to identify those who had urine cultures sent as part of their evaluation. The charts of patients with a positive urine culture were further reviewed to evaluate the diagnosis and outcome.

Five hundred twelve urine cultures were sent for analysis of preterm labor, and 6 (1.2%) reported growth of > 100,000 colonies of a single bacterium. Of these 6 patients, 5 reported symptoms consistent with a urinary tract infection, while the 6th was asymptomatic. Fisher's exact test showed no clinical significance for a positive urine culture as a predictor of preterm delivery (P = .68). Sensitivity was 0.7% (95% CI, 0.0-4.3), and specificity was 98.6% (95% CI, 96.7-99.5). A cost difference of $29,676 existed between charges and reimbursements. A positive culture was not a significant risk factor for preterm delivery. The 1 patient who delivered preterm with a positive culture probably had cervical incompetence as the cause of preterm delivery.

The routine use of urine cultures in the assessment of preterm labor is costly and adds little value to obtaining a diagnosis except in the presence of specific complaints at our institution. Urine culture identified a single patient with asymptomatic bacteriuria being evaluated for preterm labor, and she probably had another etiology for her advanced cervical examination.