Giving antibiotics to mothers while they are giving birth affects the process of establishing the intestinal microbiota of the new born baby, according to a study led by the Spanish National Research Council (Consejo Superior de Investigaciones Científicas de España-CSIC, in Spanish) and recently published in Journal of Pediatrics. In the case of premature babies, the study says, the alterations could be even more serious.

At birth, bacterial colonization of the gut begins, and this is key to the maturation of a newborn’s immune system. Any disruption that occurs in this process, experts believe, could increase the risk of the baby suffering various diseases in the future. “In previous studies we have found large differences in the process of bacterial colonization between preterm and term infants and wanted to delve into perinatal factors responsible for these differences. We knew that breastfeeding, vaginal delivery and antibiotics could be key factors,” explains to Gut Microbiota Worldwatch Miguel Gueimonde, lead author of the study.

The first factor investigated was antibiotics. To do this, researchers started with a sample of 40 infants, 27 of whom were premature, and divided the babies into four groups according to whether they or their mothers had received antibiotics at birth or during delivery. They took stool samples from the infants after one day, after several days, after one month and, finally, after three months, and analysed the samples using technologies of mass DNA sequencing.

One of the most amazing things that the study discovered, explained Gueimonde, is that what most influence the infant microbiota are the antibiotics administered to the mothers during labour. Even a single dose has been shown to have a significant effect on the colonization process.

Giving mothers antibiotics during labour is a common practice in Spain: three in ten women receive them to avoid infection. However, this protocol is not risk-free for the baby, as it might contribute to raise the levels of enterobacteriaceae, microorganisms that may be pathogenic in the microbiota of the child for at least the first month of life. In the case of premature babies (whose microbiota, compared with that of term infants have fewer beneficial microorganisms), researchers have found that “these particular characteristics of prematurity are also increased by perinatal exposure antibiotics,” says Gueimonde.

The researchers say that this study lays the foundations for rethinking protocols used during labour and for promoting the development of nutritional supplements that can help babies to compensate for the treatments that are often essential, helping the restoration of their intestinal microbiota.