Vitamin E functions as a lipid-soluble antioxidant, protecting cells of the body from damage by harmful free radicals (i.e. reactive oxygen molecules) and may have other physiological functions. Vitamin C has also antioxidant properties, and is additionally involved in the synthesis of collagen and metabolism of iron and folate.

As antioxidants, vitamins E and C act synergistically to help prevent oxidative stress, which is an imbalance in the amount of free radicals circulating in the body and the availability of antioxidants to counter the free radicals. Vitamin E and C supplementation is thus often given concurrently.

Links have been made between oxidative stress during pregnancy and the development of pre-eclampsia, and increased risk of intrauterine growth restriction and pre-labour rupture of membranes (PROM). Oxidative stress has also been implicated in many disorders common to preterm infants including chronic lung disease, necrotising enterocolitis and others. However, currently available evidence indicates that supplementation with vitamin E and C together likely has little to no effect on relevant outcomes in mothers and infants, and may in fact increase the risk of PROM.