What are Natural Killer Cells, and how can they effect pregnancy?

Natural killer cells have been in the news recently, with some reports stating they can cause miscarriages and implantation failure. But what are natural killer cells, and is there any truth to these articles?

NOW-fertility Founder Professor Luciano Nardo sorts fact from fiction:

There has been some research that demonstrates that women with raised natural killer cells may suffer miscarriages and implantation failure cycles.

What are natural killer cells?

Natural killer cells are very important cells in our bodies. They are a type of lymphocyte, or white blood cell, and are critical for our innate immune response. They control our immune system, and are responsible for protecting our body from any external assault.

The cells provide a rapid immune response to any cells or organisms that may invade our body. Natural killer cells are especially unique in the way they work, because they are faster than any other type of immune cell in the body.

The link with miscarriage and failed implantation

An embryo is at least 50 percent external cells from the mother. As a result, it has been speculated that the mother’s cells in the body could create a hostile environment within the uterus, and the natural killer cells are rapidly activated to ‘protect’ the body. While we need these cells to safeguard ourselves, in some cases raised natural killer cells may prevent an embryo from implanting, stopping a pregnancy from continuing. The natural killer cells are the controller of the barrier between the embryo and the uterus.

However, it is important to note that natural killer cells aren’t the only cause of repeated miscarriages or implantation failure. Early pregnancy losses can be linked to a number of underlying issues, and it is important to speak with your doctor about your personal medical history.

Testing for natural killer cells

There isn’t a consensus for whether we should test all women for natural killer cells. You can test for natural killer cells by doing a blood test, or by taking a biopsy of the lining of the endometrium (the mucous membrane lining the uterus) and sending it for further analysis.

Even if you have natural killer cells in your blood, they are not always found inside the uterus. However, in my professional opinion, if there is a history of repeated implantation failure and recurrent miscarriages, and natural killer cells have been found in your blood, it is indicative that there is an environment inside your body that is trying to protect the individual.

Treatment for natural killer cells

The treatments for natural killer cells are still very controversial, and we need to make sure that we are not causing harm. We can’t lower the immune system, as it can cause wider health issues. I would normally prescribe low dose steroids, discussing potential side effects and next steps with my patient.

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