Various things during delivery can have an affect on the physiology and the immune system of a child. The first and most important thing is the difference between a vaginal birth and a Caesarean section. Oxidative stress, hypoxia, interactions with the mother's hormones and the effect of different forces on a child all happen during a vaginal birth and are not present during the Caesarean section. Due to the lack of all these stressful situations and interactions, the child may develop anatomical deformities such as underdeveloped lungs or an underdeveloped immune14 system, e.g. they have a reduced amount of interferon y. To prevent this, certain substances like corticosteroids that stimulate lung development after birth can be used. A microbiom located in the vaginal tract is also avoided with the C-section. That can cause a weakened immune system and certain pathological conditions like infections. This can potentially be solved by exposing the child to the vaginal microbiom after birth. During vaginal labour different epigenetic mechanisms that affect gene expression are activated by the stress that a child goes through during labour. That stress is reduced during Csection so those mechanisms don't get activated. In case of premature delivery (before the 37th week) the child has a weakened immune system. As with normal delivery, the child does not yet have an acquired immune system, but relies on the innate one. The innate immunity is not fully developed in prematurely born children because of the lack of leukocytes responsible for this so the child is more susceptible to pathological conditions such as sepsis. A child born like this needs to be isolated from interactions with the environment and its' immune system development should be helped with the mother's milk which contains the mother's antibodies.