Bottom Line Up Front
The ERA (Endometrial Receptivity Analysis) is a biopsy-based test that identifies your personal “window of implantation” — the specific hours when your uterine lining is most receptive to embryo implantation. Approximately 25–30% of women have a displaced window (earlier or later than the standard day 5 after progesterone start). In Colombia, the ERA costs $800–$1,500 compared to $1,500–$3,000 in the US.
In a standard frozen embryo transfer, the embryo is placed in the uterus on the 5th day of progesterone supplementation, based on the assumption that this is when the endometrium is receptive. For most women, this timing works. But for a significant minority, the window of implantation is displaced by 12–24 hours in either direction. This means that a perfectly healthy embryo is being placed in a uterus that is not yet ready (pre-receptive) or has already passed its receptive phase (post-receptive).
The ERA test was developed by Igenomix (now part of Vitrolife) and has been validated in multiple studies. It analyzes the expression of 248 genes in the endometrial tissue to determine whether the lining is receptive, pre-receptive, or post-receptive at the time of biopsy.
Who Should Consider the ERA?
The ERA is most valuable for patients with recurrent implantation failure — specifically, those who have transferred two or more chromosomally normal (PGT-A tested) embryos without achieving implantation. If good embryos are not implanting, the problem may not be the embryo. It may be the timing.
The test is less valuable (and generally not recommended) for patients who have not yet attempted a transfer, or for those whose failed transfers involved untested embryos (where chromosomal abnormality, not timing, is the more likely explanation for failure).
How the ERA Works
The ERA is performed in a mock cycle — a cycle where no embryo transfer is planned. You take the same estrogen and progesterone medications you would take for a frozen embryo transfer, preparing the uterine lining exactly as you would for a real transfer. On the day the transfer would normally occur (day 5 of progesterone), a small tissue sample is taken from the uterine lining via an endometrial biopsy.
The biopsy is a brief procedure (less than 60 seconds of active sampling) performed in the clinic without anesthesia. Most patients describe it as uncomfortable, similar to a strong menstrual cramp, but tolerable. The sample is sent to the lab for gene expression analysis, with results available in 2–3 weeks.
Interpreting ERA Results
| Result | What It Means | Action |
|---|---|---|
| Receptive | Your window aligns with standard timing | Transfer on standard day 5 of progesterone |
| Pre-receptive | Your lining needs more progesterone exposure | Transfer 12–24 hours later than standard |
| Post-receptive | Your window has already passed | Transfer 12–24 hours earlier than standard |
| Non-receptive | Significant displacement | Repeat ERA with adjusted timing to find your window |
Does the ERA Improve Pregnancy Rates?
The evidence is growing but not definitive. A large randomized trial (the ERA-RCT) showed no overall benefit for unselected IVF patients. However, subgroup analyses and observational studies suggest meaningful benefit for patients with confirmed displaced windows (the 25–30% whose timing is off). For recurrent implantation failure patients specifically, personalized embryo transfer timing based on ERA results has shown improved outcomes in several studies.
Had Repeated Failed Transfers?
The ERA may reveal a timing issue that a simple adjustment can fix. Ask a Colombian specialist whether it makes sense for your situation.
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