Find out how to prepare for embryo transfer and learn how important the implantation window is for embryo implantation
. Watch the video recording from our webinar with Dr. Roksolana Semchyshyn, Ph.D., M.D., from Intersono Clinic.
How important is an embryo implantation window?
In IVF it is widely understood that for successful implantation to occur, a good quality embryo needs to be transferred. Whilst it certainly plays a hugely important role in achieving a pregnancy, embryonic health isn’t the only factor.
In this webinar Dr Roksolana Semchyshyn, a fertility doctor and head of the IVF department at Intersono clinic, Ukraine, explains the importance of a healthy endometrium, outlining the window of implantation and describing what happens after an embryo is transferred.
Before explaining why the uterine lining is so important, Dr Semchyshyn advises that patients need to understand the process of implantation, and how the partnership between the endometrium and the embryo works.
Following the fertilisation procedures of IVF, an embryo is transferred into the female’s uterine cavity. Implantation does not take place immediately and, once in utero, an embryo will start searching for the right place to implant. As it does, it transmits signals which the endometrium reads and then uses to understand whether, or not, the embryo is good enough to implant. However, this all-important communication, between the embryo and the uterine lining
, will only take place if the endometrium is healthy and has a normal structure. For any embryos permitted to implant, that usually happens around four to five days after the transfer.
The main function of the endometrium is to provide the most suitable conditions for an embryo to implant. Abnormal inclusions, such as polyps, can be a factor of unsuccessful implantation, as can IVF itself.
Due to the medically induced suppression of the endometrium during the down regulation process, a woman’s body is sometimes unable to read the signals emitting from the embryo. In order to check whether the endometrium is fully healthy to receive the embryo, regular ultrasounds are crucial.
Screening is also imperative to check on the thickness of the uterine lining in advance of the transfer. Dr Semchyshyn advises that an appropriate measurement of the endometrium is essential for increasing the chances of pregnancy
. For an embryo to implant properly it needs enough space to embed into the endometrial lining. If this lining is too thin there will be a decreased blood flow to the uterus and the embryo may not be able to implant correctly. On the other hand, if the lining is too thick this could make it more difficult for the embryo, and could also lead to hyperplasia; a continued, abnormal growth of the endometrium.
According to Dr Semchyshyn a lining which measures between 8-14mm is ideal or, when undergoing a cryo (frozen) cycle, from 7mm.
For women who have repeatedly failed to become pregnant, following the transfer of healthy embryos,
a hysteroscopy may be recommended.
In this procedure a camera is used, in utero, enabling medical teams to see the uterine cavity more clearly than on an ultrasound. Intersono clinic has noticed a higher pregnancy rate in patients who undergo this procedure, however, there is no evidence that it is a benefit for all patients undergoing IVF, and hysteroscopies should not be routinely advised for everyone.
Whether conceiving naturally or by IVF the window of implantation is critical for a successful pregnancy.
Every woman is different but, on average, this window typically takes place around day 20-24 of a woman’s cycle, which is circa 6-8 days after ovulation. It lasts for 48 hours. In IVF, the window of implantation is effectively the timeframe when embryos need to be transferred into the uterus; it’s when the endometrium is at its most responsive.
If IVF with good quality embryos has been unsuccessful then an ERA (Endo Receptive Array) test may be recommended. An ERA is used to detect when the endometrium is at its most receptive.
By conducting this type of biopsy, medical teams are able to look at the genes responsible for implantation, determining when they are at their most active. This will then tell doctors when the transfer should take place.
For a woman to conceive her body needs to be “baby friendly” which, in part, means having good immunological health. Dr Semchyshyn describes the body’s immune system as the “bodyguard of our organisms,” and advises that clinics should run immune testing on female patients who have suffered repeated IVF failure or recurrent miscarriage.
May NK cells prevent implantation?
NK (Natural Killer) cells are thought to prevent implantation. These are activated when viruses or bacteria are present in the body’s organisms, rejecting any virally infected cells. When a woman becomes pregnant the pregnancy creates a conflicting situation for the immune system, as the embryo is not natural to the body’s cells. If the immune system doesn’t function properly then these NK cells can become highly aggressive and detrimental to implantation, and /or ongoing foetal development. Immunogram testing can checks for NK levels within the blood or the endometrium cells. The more information medical teams can learn from each patient, the more they can understand whether the immune system is operating correctly. If any immunological issues are discovered, then clinics can surgically treat and / or medicate, which gives any subsequent pregnancies additional help to proceed.
Can HLA hinder the implantation?
Another immunological factor which can hinder implantation is HLA (Human Leucocyte Antigens). In simple terms, antigens are the surface of the blood cells in the human body. When creating a healthy pregnancy, any offspring need to inherit half of the antigens from the mother and half from the father; both sets need to be different. If the inherited genes are too similar then the mother’s body will not recognise the pregnancy, meaning her immune system is unable to trigger the immunological response which is required to protect and preserve the pregnancy. Dr Semchyshyn explains that, again, clinics can test to determine whether tissue compatibility could be the reason for failed embryo implantation.
Medical teams should also analyse the thyroid gland of patients who are struggling to conceive, even with assisted reproduction techniques. Thyroid glands are usually hidden from the body’s immune system and it’s only when the immune system isn’t working properly, that it starts to notice the thyroid gland and attack it. Or, in the cases of pregnant women; attack the baby. If the correct tests are conducted, then any problems can be diagnosed and treated in advance of the embryo transfer. Once a pregnancy is established, medication can also be administered to provide ongoing prenatal thyroid support.
“Unexplained fertility generally means that the physician failed to find the true cause of infertility” said Dr Norbert Gleicher and Dr Semchyshyn agrees..
Greater reproductive knowledge is continually amassed, and further testing and analysis can now be carried out to help couples find out exactly why they are struggling to conceive. With correct clinical procedures and medical guidance, patients should be offered a diverse range of protocols to prepare for individualised embryo transfers, most suited to their particular needs. Medical teams have a duty to patients to be thorough in their screenings, recommending specialised regimens based on medical and fertility treatment history, alongside current, comprehensive test results.
When it comes to preparing the endometrium, regular and detailed ultrasound and hormonal monitoring are absolutely key. Combine a good quality embryo with a healthy endometrium and immune system, and the probability of successful implantation leading to a healthy pregnancy and live birth is greatly improved.