What is the implantation window and why it’s that important?

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The window of implantation and its importance in fertility treatment.

What is the implantation window and why it is so important in fertility treatment? What role does the endometrium play in the whole process? How long does the reception-ready phase of the endometrium last?
Watch 3on1 #IVFANSWERS to know. All those questions are answered by fertility experts :

  • Dr Alejandro Aldape Arellan – senior consultant in reproductive medicine, currently Medical Director of Institut Marquès Ireland.
  • Dr Diana Obidnyak – Head of International Cooperation Department AVA Peter Clinic
  • Dr Inna Moroz – Fertility Specialist at ISIDA IVF Clinic

Dr Alejandro Aldape Arellan , Institut Marquès, Spain

Answer from Dr Aldape Arellan - Medical Director

The implantation window is the period when the uterus is receptive to the implantation of an embryo. There is no full agreement but we can say that the implantation window can last for about two or three days. When we are talking about fresh IVF cycles, there is no clear way of evaluating that window. So there is truly no way of knowing if the window is going to be open or closed.
However, we doctors know that when the progesterone is really high, the implantation window can be compromised. When it comes to a medicated FET (frozen embryo transfer), then the story is completely different. Of course it is an artificial cycle so there is a way of checking the implantation window during a biopsy. And after doing this biopsy, we can just do the same cycle and transfer the embryo at the proper time.
So the question is: why is the implantation window so important? Because if we are transferring a really good quality embryo and the implantation window is closed, the patient is not going to get pregnant. In Institut Marquès, it is always a part of our protocol to check for the implantation window with a biopsy. We do it just to be 100% sure that we are transferring the embryo at the right time.


Dr Diana Obidnyak, AVA Peter Clinic, Russia

Answer from Dr Obidnyak - Head of International Cooperation Department

Implantation represents a very delicate crosstalk between embryo and endometrium. Interestingly, endometrium is characterised by the capability to accept and select the embryo. Thus, it plays a role of a natural biosensor of embryo competence. However, the period when endometrium is receptive to the implantation and ready to accept an embryo is very short. That’s why it’s called the implantation window. Usually, it lies between days 19 and 21 of a menstrual cycle.
Unfortunately, about 30% of women have a displaced implantation window. Undoubtedly, the information about the optimal time for embryo transfer is one of the crucial points for IVF success. Nowadays we have two technologies to identify the implantation window precisely: the ERA test and BeREADY test. In Ava-Peter clinic we have implemented both of them, providing the personalised treatment in each case of infertility.


Dr Inna Moroz, ISIDA IVF, Ukraine

Answer from Dr Moroz - Fertility Specialist

The window of implantation is a specific period of time when your endometrium is in an ideal state to accept an embryo. If you are struggling to conceive and you have failed attempts in the past, it can be related to the condition of your endometrium on the embryo transfer day. The preparation of the endometrium is a very crucial process and the thickness of the lining is the key of the IVF cycle. Picking the right time for the embryo implantation is very crucial. The hormones oestrogen and progesterone can influence the growth and the development of the endometrium during 2 phases of the menstrual cycle: the endometrial lining change in thickness and the changes in the number of glands and vessels. This all can impact the sensitivity of the inner lining of your uterus and its ability to accept an embryo on the embryo transfer day. Usually, the window of implantation is approximately on the 19th – 22nd day of a normal 28-day menstrual cycle. However, research shows that the implantation window can be displaced in 25% of women in the general population.
That’s why it is so important to understand this factor before the embryo transfer to avoid complications. The displaced window of implantation can be the reason why changes in the endometrium preparation protocol have no results or why multiple attempts fail to deliver a result even if we transfer genetically good embryos. So make sure to ask your doctor about testing this.


3on1 IVFanswers - three answers to one question

Three IVF experts answering the same question.

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