Let’s first examine why ERA was created. In unassisted reproductive physiology, an embryo does not implant into the uterine lining right away. After fertilization, it spends about three days in the Fallopian tube, where it then travels to the uterus, and takes a few more days before it implants.
The embryo transfer is performed at the same time for all women. However, it has been suggested that a proportion of women are not receptive to an embryo that is trying to implant at standard transfer timing. These women may benefit from a more targeted transfer at an earlier or later time.
ERA classifies the menstrual cycle into five phases:
- Pre-receptive phase: Before the window of implantation
- Early receptive phase: Nearing the ideal window of implantation
- Receptive phase: Ideal window of implantation
- Late receptive phase: Window of implantation is closing
- Post receptive phase: The window of implantation has closed
The goal of ERA is to determine an individual’s personal window of implantation. With ERA, physicians can isolate a patient’s unique receptive phase down to a specific, six-hour window.
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