Successful implantation is an absolute requirement for the reproduction of species, including humans. The process by which a foreign blastocyst (embryo) is accepted by the maternal endometrium (lining of the womb) is complex and requires interplay of many systems.

Implantation occurs during the specific time of “implantation window” (7-10 days following ovulation), in which the maternal endometrium is ready to accept the blastocyst, which on the other hand, also plays a specific role. It appears that immune cells and in particular, uterine NK cells are pivotal in inducing tolerance to the blastocyst.

uNK cells can secrete an array of cytokines (chemicals) that are important in angiogenesis (development of blood vessels) and thus placental development and the establishment of pregnancy.

Uterine NK (uNK) cells are present in large numbers in the wall of the womb at implantation and in the early months of pregnancy. Maternal uNK cells are adjacent to, and have the ability to interact directly with, fetal placenta. They seem to help the placenta link up with your blood vessels and so set up a healthy supply line to the fetus. However, scientists do not know exactly how they do it. (In mice that lack NK cells in the womb, development of the placenta is abnormal and the young are smaller than usual). Uterine NK cells appear to be essential and very important regulators of successful implantation and pregnancy.

There is no absolute evidence that uterine NK cells are destructive and attack placental or embryonic cells. However, recently it was suggested that abnormal regulation of NK cells in the womb and/or the blood was evident in women prone to recurrent pregnancy loss and implantation failure. In addition studies found that increased numbers of uNK cells have been associated with reproductive failure.

Increased numbers of uNK cells have been associated with reproductive failure. The mechanisms of reproductive failure associated with raised uNK cell density appear to be increased angiogenesis (blood vessel development) and peri-implantation blood flow, which may lead to early maternal circulation and hence pregnancy failure due to excessive oxidative stress.

Although the evidence regarding a link between blood and uterine NK cells is limited, it was recently shown that NK cells in the blood could reflect changes in uterine NK cell levels.

The success of in vitro fertilization and embryo transfer (IVF-ET) is contributed by a number of factors, which include the patient profile, uterine (womb) pathology, stimulation protocols, culture conditions, embryo quality and embryo transfer technique.

Implantation of the embryo, which is a prerequisite for successful pregnancy, can only take place in a receptive uterus (womb). In humans, the uterus becomes receptive during the midsecretory phase of the menstrual cycle (days 19 to 23), commonly known as the window of implantation (WOI). It is assumed that inadequate uterine receptivity is responsible for approximately two-thirds of implantation failures.

Although many fertility disorders have been overcome by a variety of assisted reproductive techniques, implantation remains the rate-limiting step for the success of in vitro fertilization (IVF).

Recent developments in reproductive medicine address oocyte (egg) morphology, sperm analysis and embryo selection. However, in a subgroup of infertile couples, it is embryo implantation process that is disrupted. Diagnostic tools to identify patients at risk of implantation failure are limited.

Implantation requires a close interaction between the fetal trophoblast (placenta) and the maternal endometrium (lining of the womb) with natural killer cells (NK cells) playing a main part at the feto-maternal interface during early pregnancy.
There is evidence to suggest that immunological implantation failure and recurrent miscarriages are more than likely mediated through activation of NK cells.

What are Natural Killer cells?

NK cells are a type of lymphocyte - an immune cell - normally circulating in blood. They make up a large part of the immune system. NK cells play a major role in the rejection of tumours and cells infected by viruses. They kill those cells by apoptosis (cell shrinkage).

There is evidence to suggest that an imbalance of activity of NK cells in the blood of some women could be contributing to miscarriage.

More recently, an imbalance in the presence of NK cells was also found in the blood of women whose embryos failed to implant in the womb.

Some clinics offer blood tests to measure the level of NK cells in your blood as well as tests that measure their function.  These blood tests will only measure NK cells in the blood and cannot measure or test NK cells in the uterus. 

We are the only clinic in the UK that is able to offer Natural Killer Cell Testing as well as Natural Killer Cell blood count and activity tests.

So Call Us Today On 0800 228 9878 or 07860 439 346