Patterns of Antibiotic Utilization and Bacterial Susceptibility of Prenatal Urinary Tract Infections

Background: Choosing antibiotics for prenatal urinary tract infections (UTIs) is challenging because fetal safety data are inconclusive and must be weighed against resistance. Recent information on prescribing patterns and antimicrobial susceptibility is sparse; we aimed to address this gap. Study Design: We used electronic health record data from two US health systems (Kaiser Permanente Washington [KPWA] and Vanderbilt University Medical Center [VUMC]) to ascertain pregnancies from January 1, 2006, to August 31, 2023, to individuals aged 15–49. We included outpatient-treated prenatal UTIs with an oral UTI antibiotic plus a diagnosis or positive urine culture. We described patterns of antibiotic utilization and susceptibility overall (2006–2023) and by year (2010–2022). Results: We identified 10,734 eligible UTIs. The most common antibiotics were nitrofurantoin (KPWA: 42%; VUMC: 65%) and first generation cephalosporins (KPWA: 23%; VUMC: 15%). Nitrofurantoin decreased substantially from 2010 to 2022 (KPWA: from 50% to 27%; VUMC: 65–49%), while first generation cephalosporins increased (KPWA: 12 to 45%; VUMC: 14 to 21%). Escherichia coli was susceptible to nitrofurantoin in 98–99% of UTIs. Susceptibility to other antibiotics was higher at KPWA than VUMC (first generation cephalosporins: KPWA: 97%, VUMC: 89%; amoxicillin–clavulanate: KPWA: 93%, VUMC: 85%). 93–95% were treated with an appropriate antibiotic based on susceptibility results. Conclusions: In two health systems in different regions, nitrofurantoin decreased substantially while first generation cephalosporins increased, despite better nitrofurantoin susceptibility. Other concerns, like malformation risk, may have influenced prescribing. Further research and guideline development are needed to weigh risks versus benefits of different antibiotics for prenatal UTIs.