title: Why we should transfer frozen instead of fresh embryos: the translational rationale.
abstract: Epidemiologic studies have shown an increased rate of adverse perinatal outcomes, including small for gestational age (SGA) births, in fresh in vitro fertilization (IVF) cycles compared with frozen embryo transfer cycles. This increase is not seen in the donor oocyte population, suggesting that it is the peri-implantation environment created after superovulation that is responsible for these changes. During a fresh IVF cycle, multiple corpora lutea secrete high levels of hormones and other factors that can affect the endometrium and the implanting embryo. In this review, we discuss both animal and human data demonstrating that superovulation has significant effects on the endometrium and embryo. Additionally, potential mechanisms for the adverse effects of gonadotropin stimulation on implantation and placental development are proposed. We think that these data, along with the growing body of epidemiologic evidence, support the proposal that frozen embryo transfer should be considered preferentially, particularly in high responders, as a means to potentially decrease at least some of the adverse perinatal outcomes associated with IVF.
authors.affiliation: Division of Reproductive Endocrinology and Infertility, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Rachel
authors.initials: R
authors.lastname: Weinerman
authors.affiliation: Division of Reproductive Endocrinology and Infertility, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: mainigim@uphs.upenn.edu.
authors.forename: Monica
authors.initials: M
authors.lastname: Mainigi
mesh_terms: D000818:Animals; D015925:Cryopreservation; D010064:Embryo Implantation / Q000187:drug effects; D004624:Embryo Transfer / Q000009:adverse effects; D004622:Embryo, Mammalian / Q000187:drug effects; D004717:Endometrium / Q000187:drug effects / Q000503:physiopathology; D005260:Female; D005298:Fertility; D005300:Fertility Agents, Female / Q000009:adverse effects*; D005307:Fertilization in Vitro / Q000009:adverse effects; D006801:Humans; D007246:Infertility / Q000503:physiopathology / Q000628:therapy*; D010062:Ovulation Induction / Q000009:adverse effects; D011247:Pregnancy; D018873:Pregnancy Rate; D018570:Risk Assessment; D012307:Risk Factors; D013480:Superovulation / Q000187:drug effects; D013997:Time Factors; D057170:Translational Research, Biomedical; D016896:Treatment Outcome
chemical_list: D005300:Fertility Agents, Female
keywords: In vitro fertilization; frozen embryo transfer; implantation; placentation; superovulation