Does Endometrial Scratch Improve Embryo Implantation and IVF Success?

The way I was trained, it was imperative that we perform an embryo transfer without causing any trauma to the endometrial lining. Oftentimes, we worked through difficult transfers to minimize the risk of getting a spot of blood on the catheter, as it was considered an ominous sign. Blood on the catheter tip was believed to reduce the chance of successful implantation. But since 2012, there has been an ongoing debate among researchers, with some suggesting that, in some cases, intentional mild injury to the uterine lining may improve implantation rates and IVF success.

In this article, we’ll explore what a uterine scratch is, how it works, why it’s used, and what the current research says about its effectiveness. 

What is the Procedure? 

Endometrial scratching is a quick, low-cost, and minimally invasive procedure that typically takes about 5 to 20 minutes.

It is performed during a simple outpatient visit using the same technique as an endometrial biopsy, where a small catheter, 3 mm in width, known as the Pipelle^®, is used to collect a small sample of tissue from the uterine lining.

IN the context of IVF, the endometrial scratch is usually performed in the luteal phase of the cycle preceding IVF.  

How Does an Endometrial Scratch Work? 

When the uterine lining is “scratched” or biopsied, a small, controlled injury triggers the release of inflammatory mediators (like cytokines and prostaglandins) that can stimulate a process called decidualization.

Decidualization is a natural biological process in which the cells that line the uterus (the endometrial stromal cells) transform into specialized, nutrient-rich cells called decidual cells.

Decidual cells:

• Create a receptive environment for embryo attachment
• Control the depth of trophoblast invasion (the cells that become the placenta)
• Release cytokines, growth factors, and immune-modulating molecules that help the embryo implant and prevent the mother’s immune system from rejecting it
• Support early placental development and vascular growth

In natural circumstances, progesterone causes decidualization to occur each menstrual cycle after ovulation. The endometrial scratch before IVF implantation is theorized to promote and enhance this process. 

Decidualization can also help slow the changes occurring in the endometrium, another benefit since the hormone levels associated with IVF can accelerate endometrial growth, potentially making the uterine lining out of sync with actual embryo development.

Over the last decade, numerous studies have examined the impact of inducing an endometrial injury on embryo implantation.

Endometrial Scratching: What the Research Says

A 2012 review of five published studies on the effects of performing an endometrial biopsy prior to or during an IVF cycle found that four of these studies demonstrated that endometrial biopsy significantly improved implantation. Suggesting that in some patients, it may even double success rates. They also found that the timing of the biopsy was critical.

In one study that involved performing the biopsy on the day of the egg retrieval, they found a dramatic reduction in the implantation and ongoing pregnancy rate; an observation that validates my previous doubts about “scratching” the endometrium.

Since these early studies, the latest high-quality evidence says about endometrial “scratching” paints an inconclusive picture: 

A landmark 2021 multicenter RCT (1,364 participants) found that doing a scratch in the cycle before IVF did not improve live-birth vs. no scratch.

A 2023 meta-analysis combined data from over 4,000 women who participated in 13 high-quality randomized controlled trials (RCTs) to determine whether endometrial scratching improves IVF or ICSI success rates.

What the researchers found:

• In this large 2023 meta-analysis, endometrial scratching might increase live birth rates from about 30% to 36%, or roughly 60 additional live births per 1,000 IVF cycles. But the findings had a low confidence ratio, meaning that the real benefit could be much smaller (or possibly none at all).
• When researchers looked for subgroup differences (for example, by age, number of failed transfers, cause of infertility, or treatment type), no specific group of patients clearly benefited more than others.
• The authors emphasized that timing might influence results, such as scratching too close to the IVF cycle, reducing benefits.
• Importantly, they advised that the findings do not justify routine clinical use. Instead, endometrial scratching should be discussed cautiously, with full counseling about the limited and uncertain evidence.

Practical takeaways

• Discuss with your doctor whether you may have had an implantation problem or if your previous unsuccessful cycles were due to poor embryo quality.
• Request that this procedure be performed before the menstrual cycle of the month you wish to proceed with IVF (prior to starting ovarian stimulation meds)
• Endometrial biopsy can be uncomfortable, so consider the use of an anti-inflammatory about an hour or so before your procedure
• If considered, it should be done after careful counseling in select scenarios, acknowledging the lack of proven benefit and small but real procedure risks.

The Bottomline on Endometrial Scratching

The most up-to-date evidence and major guidelines do not support routine endometrial scratching to improve IVF outcomes, though it may be beneficial in specific cases. 

If you’ve had unsuccessful transfers, it’s likely you and your care team will have a greater positive impact by focusing on ways to improve egg and embryo quality, adjusting transfer techniques, and assessing for other uterine factors and medical issues. 

—
Robert Greene, MD, FACOG