Cesarean delivery and risk of intestinal bacterial infection.
BACKGROUND
An individual's intestinal bacterial flora is established soon after birth. Delivery by Cesarean section (c-section) deprives the newborn of colonization with maternal vaginal bacteria. We determined whether delivery by c-section is associated with an altered risk of infection with intestinal bacterial pathogens.


METHODS
In a cohort of 1.7 million Danes born 1973-2005 we identified cases of laboratory-confirmed non-typhoidal Salmonella species, Campylobacter species, Yersinia enterocolitica, Shigella species, and Shiga toxin-producing Escherichia coli from 1991-2005 in the National Registry of Enteric Pathogens. Using Poisson-regression we estimated confounder-adjusted incidence rate ratios (IRRs) for infection according to mode of delivery.


RESULTS
During 14.0 million person-years of follow-up, 22,486 individuals were diagnosed with 1 intestinal bacterial infection. C-section was associated with a small increase in risk at age 1 to <2 years (IRR, 1.09; 95% confidence interval, 1.00-1.18) and at age 2 to <5 years (IRR, 1.08; 95% confidence interval, 1.00-1.17), but after age 5 years, there was no significant association. Assuming causality only 0.62% of intestinal bacterial infections were attributable to c-section.


CONCLUSIONS
Mode of delivery appears not to be a clinically relevant determinant of risk for intestinal bacterial infections. The possible impact of increasing frequencies of c-section on the overall burden of intestinal bacterial infections appears negligible.
Bager
Peter
P
Dept of Epidemiology Research, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark. bg@ssi.dk
Simonsen
Jacob
J
Ethelberg
Steen
S
Frisch
Morten
M
D000328:Adult; D002167:Campylobacter; D002169:Campylobacter Infections / Q000453:epidemiology; D002585:Cesarean Section / Q000009:adverse effects*; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D004926:Escherichia coli; D005260:Female; D016905:Gram-Negative Bacterial Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D006092:Gram-Negative Facultatively Anaerobic Rods; D006801:Humans; D015994:Incidence; D007223:Infant; D007410:Intestinal Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology*; D011247:Pregnancy; D012042:Registries; D012044:Regression Analysis; D012475:Salmonella; D015008:Yersinia enterocolitica; D055815:Young Adult