Disrupting primary succession during childbirth: Is there a long-term consequence?

Background/Question/Methods

Childbirth is a model system in which to study primary succession.  Microbial colonization of a child starts as they move down the birth canal.  Disruption of microbial colonization (i.e., primary succession) of the gut in newborns by antibiotics during this intrapartum period may have long term consequences on the development of a child’s immune system, ultimately resulting in atopies (i.e., asthma, allergies, and eczema).   Currently three possible explanations for the occurrence of such atopies exist, which include genetic inheritance, the hygiene hypothesis, and the microflora hypothesis. Based on the microflora hypothesis, which proposes atopies are a result of disrupted microbial colonization of the child, our goal was to determine if children exposed to intrapartum antibiotics were more likely to develop eczema than those who did not. A retrospective cohort study was conducted using survey data, medical records of women who gave birth vaginally with or without antibiotics during delivery, and pediatric records of the children. 

Results/Conclusions

A total of 436 women enrolled in the study (24.4% response rate). Because some women had multiple children who met our study criteria, the data include 508 mother-child pairs. Preliminary analyses of the data suggest that no significant relationship exists between the use of intrapartum antibiotics and the development of eczema (OR 1.23, p=0.21), allergies (OR 1.07 p=0.70), or asthma (OR 1.09, p=0.69).   However, significant associations were found between asthma diagnoses in children and antibiotics administered before two years of age (OR 2.884, p<0.05) and pre-term deliveries (OR 3.048, p<0.05).  Similarly, significant results were found between eczema diagnoses in children and antibiotics administered before two years of age (OR 2.65, p<0.05).  Duration of antibiotic exposure during the intrapartum period, antibiotics in the first 3 months of life, and birth order may be important factors that affect early microbial colonization of the gut and require further analyses.  The human microbiome is thought to encode 100-fold more unique genes than our own genome, therefore understanding how processes like primary succession of the gut are affected may help us better understand human health.