Long term impact of pre-incision antibiotics on babies born by caesarean section

Csection (2)

In the UK, about a quarter of women give birth by caesarean section. In 2011, there was a change in the NICE guideline on caesarean section (CG132) recommending switching from giving antibiotics after the umbilical cord is cut to giving antibiotics before the operation to further reduce the risk of infection, such as wound infection, in mothers. There are no known short-term harms to the baby or their mother having these antibiotics around the time of the birth.

We currently do not know, however, whether these antibiotics have any long term impact on children’s health. This research project is very timely as there is growing evidence of the role of the human microbiome (different microbes that live in and on our body) in health and disease. Antibiotics given around the time of birth alter the gut microbiome of babies, which may impact on the development of the child’s immune system and increase susceptibility to allergic and other diseases in later life.

This project draws on the growing strengths of the Institute of Applied Health Research in health informatics research (including policy evaluation using routine electronic healthcare data), biostatistics and maternal and child health. This project will combine anonymised data from several sources, including two UK primary care databases and hospital episode statistics database for England.

Project documentation (NIHR HTA research project library) 



This study will look to see if there is any long term impact of antibiotics given at the time of caesarean section on the health of children. The study findings will help women and their families to make informed decisions before caesarean section with regards to whether or not, and how, they wish to receive antibiotics before their baby is born.


Before 2011, national guidance recommended offering antibiotics to women undergoing caesarean after the umbilical cord was cut, to reduce the risk of the mother developing an infection, particularly wound infection. However, it became clear that the earlier antibiotics were given the less likely mothers were to develop an infection, although most such infections are mild and respond well to treatment. As a result, the guidance changed in 2011 to recommend giving antibiotics before the operation to reduce the risk of infection in mothers even further. Current evidence shows that the risk of maternal infection is nearly halved (from around 1 in 10 to just over 1 in 20 women) when antibiotics are given before the umbilical cord is cut compared to after.

Antibiotics given to the mother before caesarean section also reach the baby via the placenta. This does not appear to affect the health of the newborn in the short termfollowing the birth. We do not know, however, whether these antibiotics have a long term impact on children’s health. The baby’s gut during and after birth is colonised by bacteria which are vital for health and believed to be important in the development of the child’s immune system. Previous research suggests that some bacteria species are less common and some more common in babies who received antibiotics during a caesarean section compared to babies who did not get antibiotics. This microbial imbalance may affect their chances of developing health conditions such as asthma, eczema and food allergies later in life.

Design and methods:

Flow diagram v3 -C-section

To assess the longer term effects of antibiotic use in caesarean section, we will use anonymised, routine NHS information already collected by hospitals and GPs from women who gave birth in the UK between 2006-2018 (before and after the change in the national policy) and their children.  

The primary care databases (The Health Improvement Network THIN and Clinical Practice Research Datalink CPRD) together contain anonymised data from around 10% of all people registered with a GP across the UK. The Hospital Episode Statistics (HES) database contains all hospital records of mothers and their babies born in England (over 8 million births during the study period). 

We will look at a range of health conditions in children, particularly asthma, eczema and allergies, as well as infections and immune system related disorders. We will compare rates of asthma and other diseases in children born by caesarean section before and after the change in the national guidance. We will also compare their health to children whose mothers had a vaginal birth over the study period. This will ensure that any changes in the health of the children are not due to changes in other factors over time, for example, changes in the diagnosis and recording of asthma in GP medical records.

The project started in April 2018 and we hope to share the findings by April 2020.

Study limitations:

  • This study will investigate if there is a link between antibiotics given at the time of birth by caesarean section and health of children during the first five years of life. It will not be able to prove or disprove that these antibiotics cause any long term health effects;
  • Recording of data in routine healthcare databases is incomplete and not always accurate. Missing data and misclassification will dilute the strength of any potential links between antibiotics and child heath;
  • Nearly all women in the UK receive antibiotics during caesarean section in the UK, but it is not recorded in the routine databases if they received these antibiotics before or after the umbilical cord is clamped. We will therefore have to make an assumption that they received the antibiotics according to the hospital policy in the year they gave birth;

Our ability to detect differences in risk, if such exist, in rare health conditions will be limited.

Patient and Public Involvement

We have actively involved parents of young children and members of the wider public in the development of this research. They were reassured that the researchers have access only to fully anonymised data that does not allow identification of individual mothers and children.  

We work in partnership with two parent advisors who are full members of the project management team and we also have an independent parent advisor who is the member of our project steering group. In response to the parent feedback, two wider public and patient involvement activities will take place during the duration of the project with a larger group of parents to help select outcomes important for children and their families, and co-produce messages based on the project findings. This will ensure that these messages are helpful when making decisions about when to receive antibiotics at the time of caesarean section.

Project Steering Group

The Project Steering Group provides independent expert advice and oversight of this study.

The independent members of the Steering Group are:


NIHR NHS_Logo_Funded by Stamp copy

This project is funded by the NIHR HTA programme (16/150/01)  The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.


For further information about this project, please contact Dr Dana Sumilo.