Cesarean versus vaginal delivery: long-term infant outcomes and the hygiene hypothesis

Abstract

Concurrent with the trend of increasing cesarean delivery numbers, there has been an epidemic of both autoimmune diseases and allergic diseases. Several theories have emerged suggesting that environmental influences are contributing to this phenomenon, most notably, the hygiene hypothesis. This article provides background about the human microbiota and its relationship to the developing immune system as well as the relationship of mode of delivery on the colonization of the infant intestine, development of the immune system, and subsequent childhood allergies, asthma, and autoimmune diseases.

Figure 1

Fig 2. “The Old Friends Hypothesis”

Common organisms interact with dendritic cells in the GI tract, leading to increased maturation of dendritic cells. When there is interaction with these organisms again, the dendritic cells increase Treg maturation; not Th1 or Th2. This increases the baseline amount of anti-inflammatory cytokines, producing a Bystander Suppression. Another consequence of the increased number of mature dendritic cells is as they interact with self antigens, they increase the number Treg specific to these antigens. This is referred to as Specific Suppression. Together these two arms lead to tolerance of both self antigens as well as those of helpful gut organisms.