Endometrial scratching — also called endometrial injury or local endometrial injury (LEI) — is a procedure in which the lining of the uterus (endometrium) is deliberately scratched or biopsied in the cycle before an embryo transfer. It has been offered at many UK fertility clinics as an add-on treatment to improve implantation rates, typically costing £150–£300.

The HFEA currently rates endometrial scratching as an add-on with no evidence of benefit for most patients. This guide explains the evidence behind that rating.

What Endometrial Scratching Is Supposed to Do

The proposed mechanism — and the reason this treatment attracted clinical interest in the first place — is based on the idea that deliberately injuring the endometrium triggers an inflammatory and healing response that makes the lining more receptive to embryo implantation. Several early small studies and meta-analyses (before 2018) suggested a benefit.

The procedure itself involves passing a thin catheter through the cervix and scraping the endometrial lining — similar to a biopsy. It is usually done in the clinic cycle before the treatment cycle. It causes cramping, similar to a period, and takes approximately 5 minutes.

The Clinical Trial Evidence

SCRaTCH Trial (2019)

The largest randomised controlled trial of endometrial scratching, the SCRaTCH trial, was conducted across the Netherlands and published in the New England Journal of Medicine in 2019. It enrolled 1,364 women with one or more previous failed IVF/ICSI transfers who were planning a subsequent frozen embryo transfer.

Result: Endometrial scratching did not improve the live birth rate. Live birth rates were 29.5% in the scratching group vs 28.9% in the control group — no statistically significant difference.

van Hoogenhuijze et al. (2019)

A separate RCT in women undergoing a first IVF/ICSI cycle, also published in 2019, found no benefit from endometrial scratching on ongoing pregnancy or live birth rates.

HFEA Review

Following these trials, the HFEA reviewed the cumulative evidence and downgraded endometrial scratching from "limited evidence" (amber) to "no evidence of benefit" — the lowest rating in its traffic light system for IVF add-ons. The HFEA's current position:

"There is now sufficient evidence to say that endometrial scratching does not improve the chances of having a baby and we would not recommend this treatment."

Why Early Studies Showed a Benefit

The earlier meta-analyses that suggested endometrial scratching worked suffered from several methodological problems:

  • Publication bias: Studies showing a benefit were more likely to be published than null results
  • Small sample sizes: Individual studies were too small to detect modest differences reliably
  • Heterogeneous protocols: Different biopsy instruments, timings, and patient populations were pooled, making interpretation difficult
  • Lack of blinding: In trials without a sham procedure control group, patients who knew they had the procedure may have reported outcomes differently

This is a common pattern in IVF add-on research — initial enthusiasm based on small or methodologically weak studies, followed by null results in properly powered RCTs.

Should I Still Ask About Endometrial Scratching?

Given the evidence, the short answer is: no, unless you are participating in a clinical trial.

If your clinic is recommending endometrial scratching as a routine add-on, this recommendation is not supported by current evidence. Asking the clinic which evidence they are basing the recommendation on — and specifically whether they are aware of the SCRaTCH trial result — is a reasonable response.

This is also a useful test of how your clinic approaches add-ons in general. A clinic that recommends add-ons transparently, with honest discussion of the evidence, is more trustworthy than one that presents unproven treatments as established.

For a broader overview of IVF add-ons and the HFEA's evidence ratings, see IVF add-on treatments.

What About Endometrial Biopsy for ERA?

The endometrial receptivity assay (ERA) test also involves biopsying the endometrium — but for a different purpose (identifying optimal transfer timing). ERA is a distinct procedure from endometrial scratching, though both involve an endometrial biopsy. ERA has its own evidence base (also debated) and should not be confused with endometrial scratching. See recurrent implantation failure for detail on ERA.

Frequently Asked Questions

Q: My clinic recommended endometrial scratching before my FET. Should I do it?

A: Based on the current evidence, no. The SCRaTCH trial — the largest and best-designed study of endometrial scratching in the context of FET in patients with previous failed cycles — found no benefit on live birth rates. The HFEA rates this as an add-on with no evidence of benefit. You can decline it without concern that you are missing a proven treatment.

Q: Is there any patient group where endometrial scratching might help?

A: Post-SCRaTCH, there is no well-defined patient subgroup where endometrial scratching has been demonstrated to be beneficial. Earlier meta-analyses had suggested possible benefit specifically in patients with two or more failed previous cycles — but the SCRaTCH trial specifically enrolled this group and found no benefit.

Q: Could endometrial scratching cause harm?

A: The procedure itself carries a small risk of cervical discomfort, cramping, minor bleeding, and theoretical risk of introducing infection. These risks are low, but they are not zero. The procedure is also associated with cost. If there is no benefit, these minor risks and costs are without justification.

Q: Why are clinics still offering it if the evidence says it doesn't work?

A: Clinical practice updates lag behind evidence, particularly for procedures that have been widely used. Some clinics update their protocols quickly following major trial results; others are slower. The HFEA's guidance is clear, but it is not a regulatory ban — clinics can continue to offer any treatment that is not prohibited. The fact that a clinic offers endometrial scratching does not make it a bad clinic overall, but it is worth asking how they approach evidence-based care more broadly.

Q: I had endometrial scratching and then got pregnant. Didn't it help?

A: Post-hoc reasoning from individual outcomes cannot answer this question. In a 30% success rate population, 30% of people will succeed after any intervention, including ones that don't work. The pregnancy rate after endometrial scratching in the SCRaTCH trial was nearly identical to without it. Individual success after a procedure does not establish that the procedure caused the success.

This article is for information only and does not constitute medical advice. Always discuss treatment decisions with your fertility specialist.