Is Frozen Embryo Transfer the New Norm in IVF?

Abstract

Frozen embryo transfer is an established, highly successful technology in Assisted Reproductive Technologies. Its use as a part of a freeze only strategy is associated with a higher probability of live birth in high responders and a decrease incidence of ovarian hyperstimulation syndrome (OHSS). Its use in normal responders, maintains the probability of live birth compared to fresh embryo transfer and decreases the incidence of OHSS. Obstetric n neonatal outcomes in frozen as compared to fresh embryo transfer cycles are characterized by a decreased incidence of monozygotic twinning, of ectopic pregnancy, of small for gestational age babies, of premature labour, of antepartum hemorrhage and of perinatal mortality. On the other hand, an increased incidence of pregnancy induced hypertension, has been observed in frozen as compared to fresh embryo transfer cycles. This, however, appears to be associated with the absence of corpus luteum during endometrium preparation for embryo transfer, as is the case in frozen embryo transfer cycles using hormonal replacement. Overall, the increased efficacy and a safety present, if fresh embryo transfer following ovarian stimulation is avoided, redefine what should be the norm in modern in-vitro fertilization practice.