Endometrial Receptivity Analysis (ERA): What Intended Parents Need to Know

Introduction

When IVF or surrogacy doesn’t work the first time, many intended parents are left asking “why?” Often the embryo is the main factor, but sometimes the uterus might not be ready at exactly the right moment. This is where the Endometrial Receptivity Analysis (ERA) test comes in. Marketed as a way to find a woman’s unique “window of implantation,” ERA has gained attention as a possible solution to repeated IVF failures.

But does ERA really work? Recent studies and expert guidelines provide important answers. In this blog, we’ll explain what ERA is, how it works, what recent research shows, the controversies around it, and who might consider it. Our goal is to help intended parents and surrogates understand whether ERA might be useful in their journey.

What Is the ERA Test?

The ERA test is a molecular diagnostic that looks at gene activity in a small piece of the uterine lining (endometrium). It’s performed during a special “mock cycle” that mimics a frozen embryo transfer. Instead of placing an embryo, doctors take an endometrial biopsy.

The lab then analyzes hundreds of genes to determine if the lining is:

• Receptive: ready for embryo implantation at the standard time.
• Pre-receptive: not ready yet (suggesting the transfer should happen later).
• Post-receptive: already past the optimal window (suggesting the transfer should be earlier).

The goal is to personalize the timing of embryo transfer (known as a personalized embryo transfer or pET) so that the embryo arrives during the woman’s unique “window of implantation.”

Why Timing Matters in IVF and Surrogacy

In a natural cycle, the uterus is only receptive to an embryo for a short period – typically a few days about one week after ovulation. In IVF, frozen embryo transfers are usually timed with hormones to replicate this window.

The ERA test suggests that some women may have a slightly shifted window, meaning the standard protocol could miss their ideal timing. By adjusting progesterone exposure before transfer, ERA aims to improve the chance of implantation.

What Does the Research Say?

Large Randomized Trials

The most important study was published in JAMA (2022). Nearly 800 women with healthy embryos were randomly assigned to ERA-guided transfers or standard transfers. The results: live birth rates were the same in both groups (about 59–62%)【JAMA 2022】. In other words, using ERA did not improve outcomes compared to standard timing.

Studies in Repeated Implantation Failure (RIF)

ERA was originally designed for women with repeated IVF failures. Some small studies suggested it might help this group. A few reported pregnancy rates of 50–70% when ERA was used after multiple failed transfers.

But more recent analyses paint a different picture. In multicenter trials and reviews, women with RIF had similar success rates whether or not they did ERA. In some studies, those who skipped ERA actually had slightly better results. As of 2025, no large trial has shown a clear benefit of ERA in RIF patients.

Key Takeaway from the Evidence

Across both good-prognosis patients and those with RIF, ERA has not consistently been shown to increase pregnancy or live birth rates. The best current evidence suggests ERA is not helpful for most IVF patients.

Controversies and Limitations

1. Lack of proven benefit: Despite being available for over a decade, ERA has not demonstrated a reliable improvement in IVF outcomes.
2. Most failures are due to embryos, not timing: Many embryos don’t implant because of chromosomal abnormalities, which ERA cannot fix.
3. Cycle variability: The window of implantation may shift between cycles, so results from one biopsy may not always apply to the next transfer.
4. Cost and delay: ERA requires an extra cycle, biopsy, and cost (often $1,000–$1,500 in the U.S.), which may not be worth it given the uncertain benefit.
5. Emotional toll: Being told your uterus is “out of sync” may add anxiety, when in fact most women implant successfully with standard timing.

What Do Guidelines Say?

• ESHRE (Europe, 2023): Endometrial receptivity tests, including ERA, are not recommended for routine use, even in women with recurrent IVF failures. They should only be considered in research or exceptional cases.
• ASRM (U.S.): ERA is not endorsed as standard practice. It may be considered in repeated unexplained failures, but patients should be informed that evidence does not show a clear benefit.
• Major fertility centers: Clinics like Mayo Clinic and others in the U.S. generally do not use ERA routinely. It’s considered an optional add-on rather than a proven treatment.

ERA in Surrogacy

Intended parents sometimes ask if their gestational surrogate should have an ERA test before transfer. Generally:

• Not recommended for first transfers. Surrogates are chosen for proven fertility, so their implantation window is likely normal.
• May be considered after a failed transfer. If a surrogate with a strong track record has an unexplained failed transfer with a good-quality embryo, some clinics might suggest ERA to rule out timing issues.
• Still experimental. Even in surrogates, ERA has no proven benefit and is not part of standard protocols.

Who Might Consider ERA?

You might consider ERA if:

• You’ve had multiple failed embryo transfers with no clear explanation.
• You are willing to invest in an experimental add-on for peace of mind.
• You’ve discussed with your doctor how ERA results would change your plan.

You probably don’t need ERA if:

• This is your first IVF or surrogacy transfer.
• You have known issues explaining implantation failure (such as embryo quality or uterine conditions).
• You prefer not to delay treatment or pay for unproven add-ons.

❓ Frequently Asked Questions (FAQs)

1. What is the ERA test in IVF?

The ERA (Endometrial Receptivity Analysis) test is a molecular test that analyzes a sample of the uterine lining to determine the best time for embryo transfer. It identifies whether the uterus is prereceptive, receptive, or postreceptive.

2. Does the ERA test improve IVF success rates?

According to large studies, including a 2022 trial in JAMA, ERA has not been proven to increase live birth rates compared to standard embryo transfer timing. For most patients, it does not make a significant difference.

3. Who should consider the ERA test?

ERA may be considered for women or surrogates with multiple unexplained failed embryo transfers (recurrent implantation failure). It is not generally recommended for first-time IVF patients.

4. Is the ERA test painful?

The test involves an endometrial biopsy, which can cause cramping and spotting similar to a heavy period. Most women tolerate the procedure well.

5. How much does the ERA test cost?

In the United States, the ERA test typically costs between $1,000–$1,500. Costs vary by clinic and are usually not covered by insurance.

6. Does my surrogate need an ERA test?

In most cases, no. Surrogates are carefully screened and usually have normal implantation timing. ERA may be considered only if a transfer fails unexpectedly.

7. Can the ERA test guarantee pregnancy?

No. The ERA test only evaluates timing. Implantation also depends on embryo quality, uterine health, and other factors. Even with “perfect” timing, pregnancy is not guaranteed.

8. Are there risks to the ERA test?

The main risks are mild cramping, spotting, and the cost and delay of an extra cycle. Serious complications are extremely rare.

Conclusion

The ERA test was created to personalize embryo transfer timing, but recent high-quality research shows it does not reliably improve IVF or surrogacy success rates. Most failures are due to embryo factors, not a mistimed uterus.

For intended parents, the decision to do ERA should be made carefully. It may be worth discussing after repeated unexplained failures, but it is not recommended for everyone. Leading fertility societies advise against routine use.

The best path forward is to focus on proven factors – embryo quality, uterine health, and good medical care – and approach ERA as an optional tool with uncertain value. If you’re considering ERA, talk openly with your fertility specialist to decide if it makes sense for your unique journey.

References

1. Doyle N. et al. (2022). Effect of Timing by Endometrial Receptivity Testing vs Standard Timing of Frozen Embryo Transfer on Live Birth. JAMA, 328(21): 2117–2125.
2. Cimadomo D. et al. (2023). ESHRE Good Practice Recommendations on Recurrent Implantation Failure. Human Reproduction Open, 2023(3).
3. University of Melbourne IVF Evidence Summary (2025). Endometrial Receptivity Array Test (ERA test).
4. Garcia-Velasco JA. et al. (2023). Endometrial receptivity tests in reproduction: a SWOT analysis. AJOG Global Reports, 3(3).
5. ASRM Practice Committee (2021–2023). Expert opinions on IVF add-ons and endometrial receptivity testing.