URGENT UPDATE: New research reveals that treating urinary tract infections (UTIs) with trimethoprim-sulfamethoxazole (TMP-SMX) during the first trimester significantly increases the risk of congenital malformations compared to other antibiotics. Conducted by researchers from Vanderbilt University and Washington University, this population-based cohort study highlights the immediate need for revised antibiotic prescribing practices for pregnant individuals.
The study, published in JAMA Network Open on July 15, 2025, analyzed data from 71,604 pregnancies involving individuals aged 15 to 49 who received first-trimester antibiotic treatment for UTIs. The findings confirm that while untreated UTIs can lead to severe perinatal complications, the choice of antibiotic is critical. Specifically, TMP-SMX is associated with a 35% increased risk of any congenital malformation compared to β-lactam antibiotics.
With untreated UTIs linked to serious outcomes like preterm birth and low birth weight, the urgency of effective treatment is clear. However, the risk associated with TMP-SMX raises alarming questions about its routine use. Out of the cohort studied, 59.2% were treated with nitrofurantoin, 4.9% with TMP-SMX, 5.1% with fluoroquinolones, and 30.8% with β-lactams.
The study revealed that the unadjusted absolute risk of congenital malformations per 1,000 infants was notably higher for TMP-SMX at 26.9, compared to 19.8 for β-lactams. The risk of severe cardiac malformations from TMP-SMX exposure was particularly concerning, with a risk ratio of 2.09.
Despite guidance from the American College of Obstetricians and Gynecologists (ACOG) recommending caution with TMP-SMX, it remains widely prescribed, with both TMP-SMX and nitrofurantoin comprising over half of first-trimester UTI prescriptions. This disconnect between guidelines and clinical practice underscores the need for immediate reevaluation of antibiotic choices in early pregnancy.
The researchers used comprehensive data from the Merative MarketScan Commercial Database and advanced statistical methods to control for various demographic and health factors. Their findings support ACOG’s recommendation to limit TMP-SMX use while suggesting that nitrofurantoin may still be safe under certain conditions.
As the medical community processes these significant findings, pregnant individuals and healthcare providers are urged to consider alternative antibiotic treatments to mitigate risks. The implications of this study are profound, affecting countless pregnancies and highlighting the importance of informed medical decisions.
Stay tuned for further updates as this story develops. For more details, refer to the original study by Sarah S. Osmundson and colleagues, published in JAMA Network Open.
This urgent news underscores the critical intersection of maternal health and medical practices that can shape the futures of newborns. Sharing this information could save lives—stay informed, stay proactive.