MTHFR and thrombophilia: The other main risk factors for PVT include prematurity (PM), low birth weight, sepsis, perinatal asfixia, thrombophilia, congenital heart disease, prolonged UVK, blood product transfusion and thrombophilia mutations such as F V Leiden, methylenetetrahydrofolate reducatese (MTHFR) in most studies.