LJUBLJANA, SLOVENIA – Delivery by C-section – especially when elective – carries a significantly higher hospitalization risk for severe infection in the first 5 years of life than vaginal delivery in a study of nearly 7.3 million singleton deliveries in four asset-rich countries, , reported at the annual meeting of the European Society for Paediatric Infectious Diseases.
“This is something that obstetricians might need to consider when discussing with the family the pros and cons for an elective C-section, particularly one that isn’t otherwise indicated for the baby or the mother,” said Dr. Burgner of the Murdoch Children’s Research Institute in Melbourne.
He presented an observational study of 7.29 million singleton births in Denmark, Great Britain, Scotland, and two Australian states during 1996-2015. C-section rates ranged from a low of 17.5% in Denmark to 29.4% in Western Australia, all of which are greater than the 10%-15% rate endorsed by the World Health Organization. Elective C-section rates varied by country from 39% to 57%. Of note, pediatric hospital care in all four countries is free, so economic considerations didn’t drive admission.
The impetus for this international collaboration was to gain new insight into the differential susceptibility to childhood infection, he explained.
“We know from our clinical practice that pretty much all of the children are exposed to pretty much all potentially serious pathogens during early life. And yet it’s only a minority that develop severe infection. It’s an extremely interesting scientific question and an extremely important clinical question as to what’s driving that differential susceptibility,” according to the pediatric infectious disease specialist.
There are a number of established risk factors for infection-related hospitalization in children, including parental smoking, maternal antibiotic exposure during pregnancy, and growth measurements at birth. Dr. Burgner and coinvestigators hypothesized that another important risk factor is the nature of the microbiome transmitted from mother to baby during delivery. This postnatal microbiome varies depending upon mode of delivery: Vaginal delivery transmits the maternal enteric microbiome, which they reasoned might be through direct immunomodulation that sets up protective immune responses early in life, especially against respiratory and gastrointestinal tract infections. In contrast, delivery by C-section causes the baby to pick up the maternal skin and hospital environment microbiomes, but not the maternal enteric microbiome.
Thus, the investigators hypothesized that C-section poses a greater risk of infection-related hospitalization during the first 5 years of life than does vaginal delivery, and that elective C-section poses a higher risk than does emergency C-section because it is more likely to involve rupture of membranes.
The center-specific rates of C-section and infection-related pediatric infection, when combined into a meta-analysis, bore out the study hypothesis. Emergency C-section was associated with a 9% greater risk of infection-related hospitalization through 5 years of age than was vaginal delivery, while elective C-section was associated with a 13% increased risk, both of which were statistically significant and clinically important.
“We were quite taken with these results. We think they provide evidence that C-section is consistently associated with infection-related hospitalization. It’s an association study that can’t prove causality, but the results implicate the postnatal microbiome as the most plausible explanation in terms of what’s driving this association,” according to Dr. Burgner.
The association between C-section and infection-related hospitalization was persistent throughout the preschool years. For example, the increased risk associated with elective C-section was 16% during age 0-3 months, 20% during months 4-6, 14% in months 7-12, 13% during ages 1-2 years, and 11% among 2- to 5-year-olds, he continued.
The increased risk of severe preschool infection was highest for upper and lower respiratory tract and gastrointestinal infections, which involve the organ systems most likely to experience direct inoculation of the maternal microbiome, he noted.
Because the investigators recognized that the study results were potentially vulnerable to confounding by indication – that is, that the reason for doing a C-section might itself confer increased risk of subsequent preschool infection-related hospitalization – they repeated their analysis in a predefined low-risk subpopulation. The results closely mirrored those in the overall study population: an 8% increased risk in the emergency C-section group and a 14% increased risk with elective C-section.
Results of this large multinational study should provide further support for ongoing research aimed at supporting the infant microbiome after delivery by C-section via vaginal microbial transfer and other methods, he observed.
Dr. Burgner reported having no financial conflicts regarding the study, which was cosponsored by the National Health and Medical Research Council of Australia, the Danish Council for Independent Research, and nonprofit foundations.