When and why to undergo an endometrial biopsy

As specialists in assisted reproduction we are continuously researching new techniques to improve treatment success rates. Today we are going to talk about the benefits of an endometrial biopsy.

What is the endometrium?

Simply speaking, the endometrium is the active layer which lines the inner walls of the uterus. When stimulated by hormones (either from the ovary or external hormones from medication), the endometrium grows and prepares to receive the embryo which will develop there throughout pregnancy.

What is an endometrial biopsy?

It is a procedure which is performed in the doctor’s consultation room without sedation or anaesthesia. After placing the speculum, the cervix is visualised and a thin tube is inserted to collect some endometrial tissue. The procedure allows us to obtain a sample to send off to the laboratory for different types of analyses.

Is it a painful test?

The feeling is generally described as being similar to slight menstrual discomfort. It is recommended that the patient come to the appointment with a full bladder as this will ease the passage of the tube into the cervix.

What information can we obtain from the material analysed from the endometrial biopsy?

The studies we can carry out include:

  • Histological (tissue) examination to evaluate the maturity of the endometrial tissue and to rule out the presence of malignant cells.
  • Cultureto rule out endometrial infections.
  • Study of plasma cells for the diagnosis of chronic endometritis.
  • Study of Natural Killer lymphocyte subpopulations to determine the immune status of the endometrium and how it can affect mother-embryo interaction, and thus embryo implantation.

Performing the endometrial biopsy at a certain time during the woman’s cycle makes it possible for us to evaluate the embryo implantation window, i.e. evaluate whether development of the endometrium corresponds to development of the embryo at the point in her cycle when we decide to place the embryos inside the uterus.

Can an endometrial biopsy help to improve chances of embryo implantation?

The “endometrial scratch” involves making a small incision (a scratch) on the endometrium, which is what is done when the biopsy is taken. It is believed that this scratching process may release biochemical factors which favour embryo implantation. The impact this has on improved implantation rates, and thus pregnancy rates, remains controversial.

In 2015, the analysis of 14 studies demonstrating moderate-level evidence was published in the Cochrane Database. The analysis concluded that performing the endometrial scratch one month prior to the embryo transfer improves gestation rates and live birth rates in women who have previously undergone one or two embryo transfers. When the scratch is performed during the same cycle (i.e. on the day of the egg retrieval), gestation rates decrease.

The decision whether to perform the endometrial scratch should be made by the Assisted Reproduction specialist on a case-by-case basis.

Another randomised clinical trial carried out in 2014 did not find any difference among patients with subfertility who underwent the endometrial scratch during the menstrual cycle prior to the embryo transfer. Upon analysing whether the patient had previously undergone an embryo transfer, it was observed that the endometrial scratch reduced chances of pregnancy.

This year, a randomised clinical trial was published which evaluated the benefits of this technique in natural cycle patients preparing for a frozen embryo transfer. No improvements in pregnancy rates were seen after performing the “scratch”.

As we can see, there are several studies which show that this procedure may potentially improve results, and others which say the opposite. The authors of these studies recommend carrying out additional research in this area, with a greater number of patients and more homogenous populations for higher quality and more reliable results.

Carla Donado Stefani – Gynaecologist
Obstetrics and Gynaecology Unit, Seville

Posted in Assisted Reproduction, Fertility, Gynaecology

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