Large for gestational age after frozen embryo transfer: an evaluation of the possible causes for this relationship

Frozen embryo transfer is associated with increased fetal weight, increased rates of large for gestational age (LGA) infants, and increased macrosomia, when compared with fresh embryo transfer or natural conception. Although the incidence of LGA births after frozen embryo transfer has been stable for several years, the pathological causes for these findings are not understood. The purpose of this review is to understand the state of current literature suggesting causes for this relationship, and to highlight areas in need of future research to potentially address and correct this finding. Our review addresses finding in the area with respect to alterations in epigenetics, differing types of embryo culture media, differing days of cryopreservation, supraphysiologic estradiol levels, and with programmed versus natural cycle endometrial preparation.