New research from a collaboration between Vanderbilt University and Washington University reveals alarming findings regarding the treatment of urinary tract infections (UTIs) during the first trimester of pregnancy. The study, published in JAMA Network Open, indicates that using trimethoprim-sulfamethoxazole (TMP-SMX) for UTI treatment is linked to a significantly higher risk of congenital malformations compared to β-lactam antibiotics.
This urgent update is crucial for expecting mothers and healthcare providers. The study analyzed data from 71,604 pregnancies among individuals aged 15 to 49 who received first-trimester antibiotic therapy for UTIs. The results indicate that while untreated UTIs can lead to severe perinatal complications such as preterm birth and maternal sepsis, the choice of antibiotic can have profound implications for fetal health.
Researchers found that the unadjusted absolute risk of congenital malformations per 1,000 infants was 26.9 for TMP-SMX, contrasted with 19.8 for β-lactams. After controlling for various factors, TMP-SMX use was associated with a risk ratio of 1.35 for any malformation when compared to β-lactams. Particularly concerning are the findings related to severe cardiac malformations, where TMP-SMX use resulted in a risk ratio of 2.09.
Despite recommendations from the American College of Obstetricians and Gynecologists (ACOG) to limit the use of TMP-SMX during the first trimester, many clinicians still prescribe this antibiotic, making up more than half of first-trimester UTI prescriptions. The study highlights the need for adherence to these guidelines, emphasizing the potential dangers for developing infants.
The findings also revealed that nitrofurantoin and fluoroquinolones do not show a clear increased risk of malformations compared to β-lactams, suggesting they may be safer alternatives for treating UTIs during early pregnancy.
This groundbreaking study underscores the importance of routine screening for asymptomatic UTIs at the initial prenatal visit, as timely and appropriate treatment is essential to mitigate adverse outcomes. With the implications of this research, healthcare professionals are urged to reconsider prescribing practices to prioritize fetal safety.
As these findings gain traction, the medical community and expectant mothers are advised to stay informed about the safest treatment options for UTIs during the critical first trimester.
For more information, refer to the complete study by Sarah S. Osmundson et al, titled “First-Trimester Antibiotic Use for Urinary Tract Infection and Risk of Congenital Malformations,” available in JAMA Network Open (2025).
Stay tuned for further updates on this developing story, as the health implications for pregnant women and their babies are significant and urgent.
