An investigation of the association between mode of birth and childhood infectious disease and asthma

Background: In the past few decades, birth has changed profoundly with a steep rise in the rates of caesarean birth in most high-income countries and elsewhere. Observational studies have linked caesarean birth to some long-term adverse health outcomes during childhood. These include asthma and its common symptom – wheezing, however little is known about the association with particular phenotypes of wheezing. There is also some evidence suggesting that caesarean birth increases susceptibility to common childhood infectious diseases, although the scope of studies available is limited. The aim of this DPhil research was to elucidate whether mode of birth is associated with an increased risk of childhood asthma or infectious disease, including those affecting the upper and lower respiratory tract as well as the gastrointestinal tract. Comparisons are made between each type of medically interventional delivery - assisted vaginal delivery, planned and emergency caesarean sections - and unassisted vaginal deliveries.
Methods: Two data sources from the UK were used to investigate these questions in children born singleton at term and without major health problems at the time of birth. The first, the Millennium Cohort Study, is a nationally representative sample of children born in 2000-2002. The second is linked administrative datasets of the population of Wales including the children born in 2002-2016. Cox regression was used to calculate hazard ratios of hospital admission for respiratory and gastrointestinal infections and asthma. Multinomial logistic regression was used to estimate the relative risk ratio for experiencing various wheezing phenotypes during childhood.
Findings: Having adjusted for confounders, planned and emergency caesarean sections were found to be risk factors of small magnitude (10-40% increase in risk) for various adverse child health outcomes. Planned caesarean sections were associated with an elevated risk of upper and lower respiratory tract infections during infancy and early childhood and persistent wheezing throughout childhood. Emergency caesarean sections were associated with increased risk of infectious diseases of the upper respiratory tract or gastrointestinal tract during infancy, and an increased risk of severe or poorly controlled asthma in later childhood. Assisted vaginal deliveries were not found to be associated consistently with any of the outcomes under study.
Conclusion: This thesis provides modest strength of evidence to suggest that caesarean sections, whether planned or emergency, may increase the risk of infections of the respiratory or gastrointestinal tract requiring hospital admission during infancy. It also provides evidence to suggest the increased risk of respiratory morbidity such as severe asthma or persistent wheezing carries on into later childhood.

Keywords: Caesarean
Upper respiratory tract infection
Mode of delivery
childhood
Mode of birth
URTI
Wales
Asthma
Method of delivery
Wheezing
Gastrointestinal infection
Perinatal
Lower respiratory tract infection
Millennium Cohort Study
LRI
URI
Method of birth
Gastroenteritis
Infectious disease
MCS
SAIL
LRTI
Advisor: Quigley, M
Kurinczuk, J