DELIVERY BY CESAREAN SECTION AND RISK OF CHILDHOOD CANCER
Studies suggest delivery by Cesarean section (CS) may impact the development of the immune system. Meta-analyses on CS and risks of type I diabetes mellitus and asthma have found risks increased by 20%. Three different mechanisms have been proposed by which CS may influence immune development; these mechanisms are expected to act differently in elective and emergent CSs.
METHODS
Danish, Swedish and Finnish national registers were used to carry out a population-based follow-up study. Data were linked to form a cohort of children born in Denmark (1968-2007), Sweden (1973-2006) and a randomly selected sample of 90% of children born in Finland (1987-2007) (N=7,029,843). Children were followed-up from birth, until the first of the following: date of cancer diagnosis, death, emigration, end of 15th year or end of follow-up. Cox proportional hazards regression was used to obtain hazard ratios.
RESULTS
In the cohort, 12.6% of children (882,907) children were delivered by CS. Around one third of the CS were elective, one third were emergent, and one third did not have sufficient information to make the separation. There were 11,181 children who received a cancer diagnosis. A CS was associated with a hazard ratio of 1.05 (95% confidence interval 0.99, 1.11) for all cancer diagnoses. No significant associations were seen for elective or emergent CS. Elevated risks were seen for some cancer subtypes (for example testis) but none reached statistical significance.
CONCLUSIONS
The results suggest CS does not influence overall childhood cancer risk. We did not see any difference between the two types of CS. Additionally it was not strongly associated with any specific childhood cancer, but power was limited for some types. Considering the high CS rates, even a small increase in risk of childhood cancer could have public health impact.