Alloimmune Disorders in Recurrent Implantation Failures after IVF/ET Procedures

Abstract

Recurrent Implantation Failures (RIF) can be defined as the absence of implantation after 2 to 6 consecutive cycles of IVF, ICSI or frozen embryo replacement cycles where the cumulative numer of transferred high-quality embryos was no less than four for cleavage-stage embryos and no less than two for blastocytes. RIF can be considered with appropriate developemental stage with determination of implantation by an increasing quantitative Human Chorionic Gonadotropin (hCG) level and usually include also biochemical pregnancies [1]. Successful pregnancy implantation is related to adequate utero-placental circulation, absence of uterine anomalities and adequate endometrial receptivity. Immunological causes and thrombophilias play important roles in implantation failure through mechanisms similar to recurrent miscarriages [2]. Pregnancy is believed to appear a period of immunomodulation with greater pro-inflammatory activity at the beginning of pregnancy and change during the second and third trimester [3].