What is an Endometrial Receptivity Assay (ERA)?
An endometrial receptivity assay (ERA) is a molecular level test used to determine the optimal timing of progesterone treatment for an embryo transfer. An ERA may be offered electively (for example, in cases with low embryo numbers), in situations where a prior embryo transfer has not worked, or for other reasons.
An ERA involves preparing the uterus using a combination of estrogen and progesterone, in an attempt to mimic the conditions for the actual embryo transfer (provide link) as closely as possible. Typically, 5 days after initiating treatment with progesterone, an in office endometrial biopsy is performed. This involves a speculum exam (similar to a pap smear), with placement of a catheter (a thin straw) through the cervix and into the uterine cavity, in order to obtain a sample of the uterine lining (endometrial biopsy). RNA is then extracted from the endometrial biopsy, and a gene expression profile analysis (a study of which genes are turned on and off) is performed on the sample. This profile is then compared to a bank of reference profiles, and used to make adjustments to obtain the optimal timing of embryo transfer after progesterone administration start.
This test confirms the best timing for the embryo’s window of embryo implantation.