Children born to mothers who received antibiotic azithromycin to help prevent infection during a cesarean delivery were no more likely to experience respiratory or gastrointestinal adverse outcomes later in life than those born to mothers who did not receive the drug, according to new data presented at the Society for Maternal-Fetal Medicine 2026 Pregnancy Meeting. 

The results were described in a follow-up study to the Cesarean Section Optimal Antibiotic Prophylaxis (C/SOAP) study, published a decade ago, which found that women randomly assigned to azithromycin had 50% fewer puerperal infections compared to a placebo group.

How azithromycin affected the neonatal microbiome and long-term outcomes, however, was unclear. 

The new follow-up study population included 505 children aged 7-14 years born to women enrolled in the original C/SOAP study between 2011 and 2014. The researchers measured for childhood obesity and a range of other outcomes, including atopic disease, asthma, history of respiratory illness such as pneumonia, history of respiratory symptoms such as wheezing or coughing, and clinical diagnosis of eosinophilic esophagitis or inflammatory bowel disease.

Roughly half of the children had been exposed to azithromycin, with the remainder in the placebo group. Overall characteristics, including gestational age, prevalence of maternal obesity, and birth weight, were similar between the two groups. 

The rate of childhood obesity in the azithromycin-exposed children was similar and slightly lower than in the placebo group in an adjusted analysis (26.7% vs 34.4%). Rates of most secondary outcomes were similar in the azithromycin group compared with the placebo group. Microbiome-mediated gastrointestinal disorders were significantly lower in the azithromycin group (3.5% vs 8.0%). 

Akila Subramaniam, MD, associate professor of ob/gyn and maternal and fetal medicine at UAB Medicine, Birmingham, Alabama, who led the research, said she expected azithromycin to show a solid safety profile but “it was surprising that some outcomes may be improved by azithromycin, pending final data analyses.”

Such improvements are plausible because infection that could result in extended antibiotic use and cause worse childhood outcomes could potentially be prevented by a protective azithromycin dose preoperatively, she said. 

Reassuring Findings 

The change in antibiotic prophylaxis with azithromycin for cesarean sections has been almost universally implemented, given the observed 50% reduction in the rate of puerperal infections, said Aleksandr M. Fuks, MD, a professor and chair of the Department of Obstetrics & Gynecology at East Tennessee State University in Johnson City.

The current study was especially important because of the increased rates of childhood obesity in the United States, said Fuks, who was not involved in the research.

Clinicians and patients can be reassured of the positive effects of adding azithromycin to cesarean section prophylactic antibiotics without adverse effects related to childhood obesity, he said. 

“Longer-term follow-up of data on respiratory and neurodevelopment status on azithromycin-exposed and nonexposed fetuses is essential for complete evaluation of the effect of this antibiotic and for comprehensive patient counseling,” he said.

The study was funded by two grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Fuks disclosed no financial conflicts of interest.