A large U.S. study has quietly overturned a widespread medical anxiety: pregnant women taking azithromycin, a common antibiotic, are not putting their babies at risk of neurodevelopmental disorders. The findings, which surprised even the researchers who conducted them, come at a time when prescriptions for the drug have been steadily declining due to fears about antibiotic resistance and potential fetal harm.
Researchers led by Xuerong Wen, Ph.D., of the University of Rhode Island examined over 15,000 mother-infant pairs across the Northeast United States, following them for an average of 5.5 years after birth. The study, published in JAMA Network Open, found no increased risk of neurodevelopmental disorders—including ADHD, autism spectrum disorder, speech and language disorders, developmental coordination disorder, and behavioral disorders—among children exposed to azithromycin in the womb compared with those whose mothers took other antibiotics or no antibiotics at all.
What caught researchers most off guard was a secondary finding: when mothers took azithromycin specifically during late pregnancy, from week 20 onward, their children actually showed lower rates of neurodevelopmental disorders overall and notably lower rates of speech and language disorders. The protective effect was substantial—children exposed to azithromycin in late pregnancy had a 41 percent lower risk of overall neurodevelopmental disorders and a 41 percent lower risk of speech and language disorder compared with children exposed to other antibiotics. When compared with no antibiotic exposure, late-pregnancy azithromycin use was linked to a 39 percent lower risk of speech and language disorder.
Wen expressed surprise at these results, particularly given the trend she has observed in clinical practice. "We've seen that azithromycin has been going down in use," she noted, a shift driven largely by concerns about antibiotic resistance and unproven worries about fetal effects. Yet among the study's 15,527 pregnancies tracked between 2012 and 2023, only 4.8 percent of mothers received azithromycin, while 19.8 percent took other antibiotics and 75.4 percent took none.
The explanation for azithromycin's apparent protective effect may lie in its unique pharmacology. Unlike most antibiotics, azithromycin possesses enhanced anti-inflammatory properties that may shield the developing fetal brain, particularly during the critical final weeks of pregnancy when neural development accelerates most rapidly. Dr. Dani Dumitriu of Columbia University, commenting on the research, emphasized that maternal inflammation during infection can cross the placental barrier and affect the fetus. "It's incredibly important to build an empirical basis for what medications we prescribe to pregnant women," she said. Azithromycin and similar drugs may work not by killing bacteria alone, but by dampening the mother's inflammatory response, thereby protecting the growing fetus from the effects of infection itself.
The study used insurance claims data from commercially insured women, a limitation that means the findings may not reflect experiences of uninsured or publicly insured populations. The researchers acknowledged other constraints, including the possibility of unmeasured genetic or familial factors, and noted that selection bias from studying only live births may have influenced results.
Wen's conclusion was pragmatic: clinicians need not abandon azithromycin entirely. Prescribed judiciously, especially during late pregnancy, it deserves reconsideration as a treatment option. For pregnant women battling bacterial infections, this evidence offers both reassurance and possibility—a reminder that rigorous science can overturn assumptions and restore trust in medications wrongly feared.