Currently, we have yet to find methods to prevent type 1 diabetes. Therefore, any relevant information that may play a role in diabetes prevention or occurrence is of particular interest to families affected by the condition. A paper entitled “Mode of Obstetrical Delivery and Type 1 Diabetes: A Sibling Design Study” ( Pediatrics; DOI.1542/peds.2014-0819), published recently in Pediatrics by authors Khashan, Kenny, Lundholm, Kearney, Tong, and Almqvist from Ireland and Sweden, discusses the association between cesarean section and type 1 diabetes and investigates “if the association remains after accounting for familial confounding by using a sibling-control design.”
In previous blogs I have discussed the “hygiene hypothesis,” which is the basis for this study. The hygiene hypothesis proposes that there is an increase in the allergic response due to the lack of exposure to childhood diseases and infection. Studies also have noted that there has been an increase in the recognition of the different microbiomes that may lead to the development of diabetes and other immune-related diseases. Our institution (Department of Endocrinology and Diabetes, Children’s National Health System), in conjunction with the Venter Institute in Rockville, Md., is currently performing a study examining the stool and urine microbiome in our patients with diabetes and their siblings to determine if there is a possibility to predict diabetes onset in siblings based on microbiome.
Clearly, mode of delivery is important in determining the exposure to different types of bacteria. Bacteria from the birth canal colonize infants born by unassisted vaginal delivery; whereas the hospital environment and the mother’s skin mainly colonize infants delivered by cesarean section. In addition, the authors reference a meta-analysis that demonstrated a 20 percent increased risk of type 1 diabetes among children born by cesarean section as compared with those born by vaginal delivery.
How was the study conducted?
The study was a population-based cohort of all Swedish single, live-term births between 1982 and 2009 that were followed by sibling-control analyses. The types of deliveries were identified as “unassisted vaginal delivery,” “instrumental vaginal delivery,” “emergency cesarean section,” and “elective cesarean section.” The authors used two types of regression tools to perform statistical analyses. The sibling analysis included siblings that were discordant (different) for both delivery mode and type 1 diabetes.
What were the results?
In a cohort of 2,638,083 deliveries, there was an increased risk of type 1 diabetes among children born by elective cesarean section, but not emergency, when compared with children born by unassisted vaginal birth. However, “the effect of elective cesarean section and instrumental vaginal delivery on childhood type 1 diabetes almost disappeared and become non-significant in the sibling-control analyses.”
What may we conclude from these results?
The authors noted that their findings suggest a small association between elective cesarean section and instrumental vaginal delivery and type 1 diabetes. However, the sibling-control results suggest that the above findings are not consistent with the effects of delivery mode and may be due to other factors, such as genetic susceptibility and environmental factors. Thus, these findings from the sibling control analysis suggest that the association of type 1 diabetes in elective cesarean sections is not causal. We do know that there are environmental factors that are positively associated with the incidence of type 1 diabetes such as infections during pregnancy, chemical exposure, increased maternal age, and Vitamin D concentrations (see previous blogs). However, this information may provide some guidance in the decision of birth method if a choice is possible.
Published On: August 11, 2014