Intended for healthcare professionals

Letters “Vaginal seeding” after caesarean section

Safety of vaginal microbial transfer in infants delivered by caesarean, and expected health outcomes

BMJ 2016; 352 doi: (Published 31 March 2016) Cite this as: BMJ 2016;352:i1707
  1. Jose C Clemente, assistant professor1,
  2. Maria Gloria Dominguez-Bello, associate professor2
  1. 1Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
  2. 2School of Medicine, New York University, New York, USA
  1. jose.clemente{at}

Cunnington and colleagues recently acknowledged that birth by caesarean delivery is associated with increased risk of metabolic and immune diseases.1 This risk is also increased by alterations of the microbiota during early development in these neonates.2 3 The authors state that “vaginal seeding” might restore the microbiota of such infants and decrease the risk of disease, but that its health benefits are unproven. Cunnington and colleagues further warn against the use of seeding without proper testing owing to the risk of infection in newborns.

Although we agree that vaginal seeding has certain risks, we would like to make the following clarifications:

  • We have shown that exposing neonates born by caesarean to maternal vaginal fluids partially normalises the microbiota to resemble that of vaginally delivered infants.4 As we indicate in our publication, no health outcomes have yet been assessed, and this needs to be done

  • Vaginal birth is the desired mode of delivery after a healthy pregnancy even for group B streptococcus (GBS) positive mothers, who are treated with antibiotics to deliver vaginally in the US. Infection risks are acknowledged in our study and led us to the use of stricter inclusion criteria (negative GBS test, no viral or bacterial infections, and acidic vaginal pH) than the current standards for vaginal delivery in the US

  • We fully agree with the authors that breast feeding should be encouraged, and unnecessary antibiotics and caesarean sections avoided.

More studies are needed to determine the health outcomes of the multiple factors that shape microbial composition in infants. Interventions that alter natural processes such as vaginal birth should be practised only when necessary, and our study represents a first step towards reducing the health costs associated with caesarean section.


  • Competing interests: New York University has filed a US patent application (No 62161549) on behalf of Maria G Dominguez-Bello, related to methods for restoring the microbiota of newborns. Jose C Clemente declares no competing interests.

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