Antibiotics and cesarean delivery: how do they affect the newborn microbiota?

Antibiotics

Before the incision and not after cord clamping: what is the current recommended timing for prophylactic antibiotic administration in women during cesarean section? And could it even worsen the disruptions to the newborn’s gut microbiota already associated with this mode of delivery? The results of a study published in Gut¹ offer some reassurance.

About this article

Created 04 March 2022

Updated 10 March 2022

Antibiotic prophylaxis reduces the risk of serious infection in women during delivery by cesarean section by 60–70%². Administration before the incision and not after cord clamping can also reduce the incidence of endometritis and global maternal infectious morbidity³. This approach is now therefore widely recommended, but nevertheless exposes the child to antibiotics before birth, with potential repercussions for his or her health and newly-formed microbiota. Dutch researchers wanted to find out whether it further altered the bacterial colonization of children born by cesarean section.

Their randomized controlled study included 40 women who gave birth by cesarean section and received antibiotic prophylaxis (cefuroxime 1500 mg), half 30 minutes prior to incision and the other half after cord clamping, and 23 women who gave birth by vaginal delivery as a control group. The gut microbiota in all infants was analyzed 1, 7, and 28 days after birth and at the age of 3 years by 16S RNA and shotgun metagenomic sequencing.

Dysbiosis in the first month following cesarean birth

Like many others before them, the researchers observed major differences in intestinal flora during the first month of life between the children born by cesarean and those born by vaginal delivery. They recorded a lower Shannon index (relative richness and abundance of species) with a reduction in bacteria from the Bacteroides and Bifidobacterium genera, and an increase in the Proteobacteria phylum, especially Firmicutes. However, these differences resolved by the age of 3 years.

No effects of antibiotic administration prior to incision

The main finding of this study was the absence of any significant difference in composition of the gut microbiota in terms of bacterial phyla or genera between the two groups of children born by cesarean section, at any point between 1 day and 3 years. Although it included only a small group of women, this study suggests that antibiotic prophylaxis prior to incision does not cause any additional disruptions to the intestinal microbiota of children born by cesarean section.

Sources

^{1. Dierikx T, Berkhout D, Eck A, et al. Influence of timing of maternal antibiotic administration during aesarean section on infant microbial colonization : a randomised controlled trial. [published online ahead of print, 2021 Nov 21]. Gut. 2021; gutjnl-2021-324767.}

^{2. Smaill FM, Grivell RM. Antibiotic prophylaxis versus no prophylaxis for preventing infection after cesarean section. Cochrane Database Syst Rev. 2014;2014(10):CD007482.}

^{3. Boselli E, Bouvet L, Rimmelé T et al. Antibioprophylaxie pour césarienne avant incision ou après clampage du cordon ? Méta-analyse. Annales françaises d’Anesthésie et de réanimation, 2009 ; 28-(10), 855-867.}