No Difference in Microbiome of Babies Born Vaginally or By C-section

A study from the US, published in Nature, found no difference in the microbiome of babies aged four to six weeks born by cesarean section or by vaginal delivery.

Researchers at Baylor College of Medicine in Houston, Texas, studied 160 pregnant women and their babies. They found that the microbiome of babies develops greatly between birth and four to six weeks of age.

The scientists collected samples from various body sites (gut, oral, nasal, skin and vagina) and stool samples from the women and their babies (healthy, full-term births) who had, by age four to six weeks, only had one round of vaccinations. Any antibiotics their mothers received and cases of diabetes were also taken into account.

The billions of bacteria, present in the skin, mouth and digestive system, that make up the microbiota were analyzed using genome sequencing.

"Infants start to show body niche separation just like an adult, meaning that the oral microbiome is distinct from the skin microbiome, which is distinct from the gut microbiome. Except in the stool, we do not see that at birth, but by four to six weeks of age we are starting to see body niche separation," said Dr. Kjersti Aagaard, professor and vice chair of obstetrics and gynecology at Baylor. "That is rather remarkable," she concludes. This suggests that the different microbiomes (skin, mouth, gut) start to mature much earlier than previously thought. In fact, the microbiome could be established in utero during pregnancy and maturation at four to six weeks could be the result of a process that begins much earlier.

What's more, the study found no difference in microbiome composition or function in babies born by c-section or vaginally.

"We perform cesarean deliveries every day for really good reasons, and we need to be cautious that we do not assign risk to the wrong source, or misattribute risk to a surgery itself rather than the underlying reason that the surgery was undertaken," Aagaard said.

These observations challenge the link, previously established by several studies, between cesarean deliveries and differences in the gut flora of newborns, thought to occur since the child doesn't come into contact with strains of bacteria carried by the mother during childbirth.

This has been linked to various health-related consequences, such as greater vulnerability to asthma and allergies or diarrhea and infections.