The factors that could alter the microbiome of newborns has been an area of intense study. Whether it’s delivery method (vaginal vs. c-section), diet (breastmilk vs. formula), or other environmental factors that may affect the microbiome. Researchers try to uncover 1) how is the microbiome changed 2) what impact does that change have.
Caesarean section recipients are usually given prophylactic antibiotics just before the procedure to prevent infections. But there have been concerns about whether these antibiotics may have a negative impact on newborns and their microbiomes if the drugs travel through the umbilical cord and reach the baby before the cord is cut. Now, a new study has confirmed that these antibiotics cause only subtle changes to the infant microbiome. Indeed, the changes were much less significant than the impact of how the babies are fed.
The findings were reported in Cell Host & Microbe in the paper, “Maternal antibiotic prophylaxis during cesarean section has a limited impact on the infant gut microbiome.”
“We decided to conduct this study because it addresses a significant clinical question with possibly profound implications for infant health,” says Trishla Sinha, MD, a PhD student at the University Medical Center Groningen in the Netherlands. “It is crucial to balance high-quality evidence of immediate benefits to the mother against equally robust evidence of any potential short- and long-term risks to the infant. Mothers often ask whether the antibiotics they take influence their child, and this study can provide assurance that they have only small effects on infant gut microbiome.”
The current study enrolled 28 mother-infant pairs. Twelve of the mothers received antibiotics before skin incision, and the other 16 received them after the umbilical cord was clamped. A total of 172 infant microbiome samples were collected at 8 different timepoints after birth, up to one year. The analysis also included data from two other similar trials for a total of 79 infants.
For the samples they collected, the researchers looked at infant gut microbiome species composition and strain variability, as well as the composition of antibiotic-resistance genes. They also looked at the composition of bile and short-chain fatty acids. In addition to information about antibiotic usage, the investigators had information about whether the infants were formula-fed or breastfed.
The results suggest that feeding mode had a significant impact on gut microbial diversity, species, and strain-level bacterial composition, as well as bile acid composition. Infants who were formula-fed had a significantly different overall microbiome profile, with feeding mode explaining 12% of the variation in overall infant gut microbiome composition during the first six weeks of life. These differences were also reflected in the bile acid profiles in the stools of these infants. Antibiotics, in contrast to feeding mode, only had subtle impacts on antibiotic resistance genes and strain variability.
“We were surprised that the antibiotics did not drastically alter the microbiome, because other research has reported a large impact of antibiotics on infant gut microbiome composition,” Sinha says. “This is probably due to the fact that it is a one-time exposure to intravenous antibiotics during birth in contrast to prolonged exposure to antibiotics throughout infancy.”
In their next study, the researchers plan to examine a group of 1,500 mother-infant pairs from the Dutch cohort called Lifelines NEXT, looking at various health, environmental, and dietary factors during pregnancy and birth, as well as factors after birth that may influence the infant gut microbiome composition. The researchers plan to follow the infants throughout childhood and into adulthood to assess the long-term impact of the infant gut microbiome on future health outcomes.
“It’s also important to realize that alterations in the gut microbiome do not immediately translate to future health outcomes for the child,” Sinha says. “These still need to be extensively studied in longitudinal studies with longer follow-up time.”
