Background Observational studies have linked Caesarean births to susceptibility to infectious disease in the offspring. We sought to assess the relationship between mode of delivery (vaginal, instrumental, planned Caesarean, and emergency Caesarean) and subsequent infectious disease in the infant, and whether breastfeeding mediates this relationship.
Methods Data were drawn from a population-based cohort (UK Millennium Cohort Study). Participants were 15,910 infants aged approximately 9 months, born at term in 2000–2001 and without major health problems at birth. The main outcomes were maternal report of hospitalisation for lower respiratory tract infection (LRTI) defined as ‘chest infection or pneumonia’ or ‘gastroenteritis’. Odds ratios were estimated using logistic regression.
Results The rate of vaginal birth in this cohort was 71% while instrumental, planned Caesarean and emergency Caesarean accounted for 10%, 9% and 10% of the births respectively.
The overall rates of hospitalisation for infectious disease were 3.5% for LRTI and 1.4% for gastroenteritis.
The odds of hospitalisation for LRTI were higher in infants born by planned Caesarean compared to those born vaginally (crude OR 1.6 95% CI: 1.2, 2.1), but not in emergency Caesarean (crude OR 0.8 95% CI: 0.6, 1.2). Many factors were accounted for, including baby’s sex, birthweight, gestational age, number of babies at birth and ethnicity as well as the mother’s age, cohabitation status, education, socioeconomic class, smoking during pregnancy and postnatally, breastfeeding duration and whether she was primiparous. After adjustment, there was a statistically significant increase in odds associated with planned Caesarean (adjusted OR 1.5 95% CI: 1.1, 2.0).
The odds of hospitalisation for gastroenteritis were slightly higher in infants born by planned Caesarean (crude OR 1.3 95% CI: 0.7, 2.1) and those born by emergency Caesarean (crude OR 1.4 95% CI: 0.9, 2.2) compared to vaginal birth. Following adjustment, emergency Caesarean showed higher odds of gastroenteritis but this association was not statistically significant (adjusted OR 1.5 95% CI: 0.9, 2.3), while planned Caesarean showed no association (adjusted OR 1.1 95% CI: 0.6, 1.8).
Preliminary findings suggest that breastfeeding does not mediate the observed increased odds of infectious disease.
Conclusion Birth by planned Caesarean, but not emergency Caesarean, is associated with statistically significant increased odds of hospitalisation for LRTI in infancy. A statistically significant association between mode of delivery and gastroenteritis was not found, although the study was limited in power because this outcome was relatively rare. Breastfeeding does not appear to mitigate the elevated odds of infectious disease seen in babies born by Caesarean in this cohort.