Women undergoing a Caesarean section generally receive preventive antibiotics shortly before their surgery to avoid infections at the site. However, there have been worries about the potential adverse effects of these antibiotics on newborns and their gut microbiomes, especially if the medication reaches the baby through the umbilical cord before it is severed. A recent study from the Netherlands has shown that while these antibiotics can make slight changes to an infant’s microbiome, these effects are considerably less significant than those associated with infant feeding methods. The results were published on August 14 in the journal Cell Host & Microbe.
“We initiated this research because it addresses a critical clinical issue that could significantly influence infant health,” explains Trishla Sinha, the lead author from University Medical Center Groningen. “It is essential to weigh the strong evidence of short-term benefits for the mother against equally solid evidence of any potential risks, both immediate and long-term, for the infant. Many mothers inquire whether the antibiotics they take affect their child, and this study offers reassurance that the impact on the infant’s gut microbiome is minimal.”
While some prior research has explored this topic, those studies were limited due to smaller sample sizes. The initial phase of the current study included 28 pairs of mothers and infants. In this group, twelve mothers received antibiotics prior to the surgical incision, while the remaining sixteen received them after clamping the umbilical cord. A total of 172 samples of the infants’ microbiomes were collected at eight different times within the first year after birth. The analysis also incorporated data from two similar trials, resulting in a total sample of 79 infants.
“Our combined analysis makes this the most extensive study conducted in this field,” states Sinha. “Moreover, our longitudinal data and the depth of metagenomic sequencing were groundbreaking.”
For the collected samples, the researchers analyzed the composition of the infant gut microbiome, including species diversity and strain variation, along with the presence of antibiotic resistance genes. They also examined bile composition and short-chain fatty acids. They considered not only antibiotic usage but also whether infants were fed formula or breast milk.
The findings revealed that the method of feeding had a substantial influence on gut microbial diversity, the variety of species, and strain-level bacterial makeup, as well as bile acid composition. Infants fed with formula exhibited a notably different microbiome profile, with the method of feeding accounting for 12% of the variation in the overall gut microbiome composition during the first six weeks of life. This was also evident in the bile acid profiles of their stools. Recent studies have underscored the vital role of the gut microbiome and bile acids in potentially developing immune disorders later in life, indicating that these early changes may have significant long-term implications. However, additional long-term research is necessary to validate these observations. In contrast, antibiotics showed only minimal effects on antibiotic resistance genes and strain variability.
“We were taken aback that the antibiotics did not have a major effect on the microbiome, especially since other studies have noted a considerable impact of antibiotics on the infant gut microbiome,” Sinha remarks. “This is likely because the exposure in this case was a single administration of intravenous antibiotics at the time of birth, rather than ongoing antibiotic exposure throughout infancy.”
In their forthcoming study, the researchers intend to examine a group of 1,500 mother-infant pairs from the Dutch Lifelines NEXT cohort, focusing on various health, environmental, and dietary factors during pregnancy and delivery, as well as postnatal elements that may shape the infant gut microbiome. They aim to track the infants as they grow through childhood and into adulthood to evaluate the long-term influence of the gut microbiome on health outcomes.
“It’s also crucial to understand that changes in the gut microbiome do not immediately correlate with future health outcomes for the child,” Sinha adds. “These relationships still require extensive investigation through longitudinal studies with longer follow-up periods.”