Maternal antibiotics (e.g. for GBS) and imbalance in baby’s gut bacteria

4464549449_f18a3a0fc6A study published in the BJOG has given us more information about the way in which antibiotics given in labour – for example as prophylaxis for group B strep, caesarean section or because of pre-labour rupture of membranes – affect the gut microbiome of the baby. This study is welcome and timely because it confirms that intrapartum antibiotics are associated with infant gut microbiota dysbiosis (or microbial imbalance) in both vaginal and caesarean and vaginal delivery of healthy term babies. The authors found that breastfeeding can modify some but not all of these effects.

The study included 198 healthy term babies, who were part of the longitudinal Canadian CHILD study. This might not sound a lot to readers used to research involving hundreds or thousands of women or babies, but it’s a good number for a study of this nature, which involved careful measurement of the babies’ fecal samples at 3 and 12 months. Results showed that,

“In this cohort, 21% of mothers received IAP for Group B Streptococcus prophylaxis or pre-labour rupture of membranes; another 23% received IAP for elective or emergency caesarean section (CS). Infant gut microbiota community structures at 3 months differed significantly with all IAP exposures, and differences persisted to 12 months for infants delivered by emergency CS. Taxon-specific composition also differed, with the genera Bacteroides and Parabacteroides under-represented, and Enterococcus and Clostridium over-represented at 3 months following maternal IAP. Microbiota differences were especially evident following IAP with emergency CS, with some changes (increased Clostridiales and decreased Bacteroidaceae) persisting to 12 months, particularly among non-breastfed infants.”  (Azad et al 2015)


For those who may be newer to this debate, here’s an excerpt from Group B Strep Explained, in which I wrote about the dilemma of antibiotic prophylaxis:

“No-one wants to put babies at unnecessary risk, but the irony is that one of the most significant consequences of current screening and treatment programmes which involve giving antibiotics to large numbers of labouring women whose babies are deemed to be at risk of disease (which is different from definitely having disease) may be that future generations will not have effective antibiotics even for babies who are diagnosed with actual disease.

Another potentially enormous but unquantifiable problem relates to an area that we are only just beginning to understand. I began this book by discussing the relationships between humans and bacteria, and scientists have started to use terms such as the human microbiome in order to discuss the range of microorganisms that live on and within our bodies. Recent research is suggesting that not only are bacteria beneficial, but they need to be passed on to the baby during birth via its mother’s vagina and have an important part to play in future health, especially relating to the gut and digestion, but in many other areas of wellbeing as well (Turnbaugh et al 2007, Collado et al 2012). Scientists and researchers are concerned about the potential risks to antibiotic overuse both in general (Blaser 2011) and to the baby whose mother receives antibiotics in labour (Neu 2007, Broe et al 2014). This latter concern is supported by the research showing that one of the risks of caesarean section is that these bacteria do not get passed on, which can lead to problems in babies (Grönlund et al 1999, Blaser 2011).

The problems arise because antibiotics are not particularly selective, and many beneficial bacteria will be killed by them, which may have considerable but as yet unquantified knock-on effects in both women and babies (Stokholm et al 2013). Antibiotics can create changes in women’s and babies’ gut bacteria and faecal flora which can cause gastro-intestinal problems and these changes might be permanent (Ambrose et al 1985) and they have been associated with an increased chance of postnatal yeast infection in women and babies (Dinsmoor et al 2005). We need more research into this area.” (Wickham 2019).

Group B Strep Explained

Group B Strep Explained; the updated second edition of a popular book which helps parents, professionals and others to understand the issues and the evidence relating to the screening and prophylactic measures offered in the hope of preventing early-onset group B strep (EOGBS) disease.

The authors of the current study have also noted that we need more research, as this is an important area about which we need to learn much more. But their work represents another important step in our knowledge of this area.



Azad MB, Konya T, Persaud RR et al (2015). Impact of maternal intrapartum antibiotics, method of birth and breastfeeding on gut microbiota during the first year of life: a prospective cohort study. BJOG. DOI: 10.1111/1471-0528.13601

Wickham S (2019). Group B Strep Explained. Second edition. Birthmoon Creations.


photo credit: A molecular model of the bacterial cytoplasm by Adrian Elcock via photopin (license)

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