​Natural Killer Cells and Miscarriage.

What are natural killer cells?

Natural killer cells (NK cells) are part of the white blood cell family and they play a vital role in defending our bodies against disease and infection. All of the organs in the human body have NK cells, and a woman’s uterus has a huge number to prevent infection getting into this very important reproductive organ. In essence, we are all animals and the basic purpose of our lives is to reproduce and pass on our genes to the next generation. Our reproductive organs are therefore very important in evolutionary terms.

Not only do NK cells help prevent infection but they also aid in conception. They can recognise a growing embryo as a ‘foreign but friendly’ group of cells/tissues and they do not attack them. This is obviously very important if a pregnancy is to be successful.

Natural Killer Cells and fertility.

Some women have an abnormally high number of these NK cells in the uterus and this can cause a big problem if they are trying to conceive. Rather than seeing the embyo as ‘foreign but friendly’, they may attack it and this may lead to infertility and recurrent miscarriages.

In some incidences, NK cells may even prevent implantation in the first place. If you have had recurrent miscarriages then you should ask your GP to check your levels of NK cells. I have a friend who had tests done after her 4th miscarriage and she discovered this was her issue. She is now 6 months pregnant after being treated.

Treatment for high Natural Killer Cells.

It could be as simple as placing you on steroids to calm your immune response to foreign cells. Steroids may reduce the number of NK cells present in the uterus to within normal range, thus allowing you to conceive and maintain a pregnancy. Your doctor should refer you to a specialist if you are found to have high NK cell levels, as treatment needs to be balanced. Treatment should reduce NK cell number to prevent damage to your precious baby, but your body must still be able to prevent infection of the uterus. By week 10 of a pregnancy your baby will start producing its own steroids so treatment can slowly be tapered off from week 12 or so. You may also be given progesterone treatment and baby aspirin. 

To find out more about Natural Killer cells and other infertility issue or reasons for miscarriage, this is a great book recommended by lots of ladies on popular trying to conceive forums. Amazon customers have given it 4.5 out of 5 stars. and you can buy a copy from Amazon here.


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15 thoughts on “​Natural Killer Cells and Miscarriage.

  1. Jimbo says:

    I have known several women who seem to miscarriage the first time they became pregnant. Would this be a prime candidate for that? My wife, for example, had a miscarriage the first time she became pregnant but never had it happen after. The doctor said it was “one of those things that happen”. We have 3 kids now.

    • Vicki says:

      Firstly I am very sorry for your loss. I had two miscarriages before conceiving my son and they were both ‘just one of those things’ also. Doesn’t help when you are in the moment as it is devastating. High NK cells usually cause repeat miscarriages so the fact your wife got pregnant successfully 3 times indicates her NK cell count would have been normal. If a woman is repeatedly miscarrying then NK cells could be the issue.

  2. Michael says:

    Hi Vicki,
    My wife suffered a miscarriage the first time she was pregnant, but then the second time was fine and we had a son.
    I don’t think it would have been due to NK cells, but still it’s something I wasn’t aware of until reading your post.
    It is great information to know, not just for me, but also you never know if maybe friends are having problems conceiving and NK cells could be the problem.
    I would feel better equipped to offer this knowledge now after reading your post.
    Best wishes,

    • Vicki says:

      Thank you for your comment and I am sorry for your loss. I am so pleased you went on to have your son. Unfortunately not many of us are aware of NK cells and how they can affect our fertility. It is not a routine test that is conducted when a woman has a miscarriage. They usually need to have 3 in order for their doctor to take notice. Losing 1 baby is hard enough, never mind 3 or more so it is important to me to make as many people aware of it as possible to prevent unnecessary heart ache.

  3. Donald Chapman says:

    This is a must read for anyone that is thinking of starting their family. Very informative and helpful. This is probably one of the most overlooked things that a young couple should me informed of. thanks for sharing.

  4. Thabo says:

    You touched on something I had absolutely no idea about. I have always thought miscarriage is just a mistake but now you have thought me about natural killer cells.

    Can I ask ..since men cannot conceive does it mean they all have natural killer cells in them?….ha ha please dont kill me on this one…Jokes
    On a serious note though I loved your article, it was very informative and also I am sorry to here about your miscarriage.

    • Vicki says:

      Hi. Thanks for your comment. Yes both men and woman have natural killer cells as part of their immune system. They play a very important role in protecting our bodies from foreign cells like bacterium. It is when we have too high a level that it starts to cause us women problems when trying to conceive.

  5. Melinda says:

    Interesting. I did not know that natural killer cells sometimes played a role in infertility. I’ll have to recommend this book to my friends who are trying to conceive.

  6. Taianne says:

    I had a sister in law who had several miscarriages and she and her husband (my husband’s brother) never did have children. After reading this I wonder if this might have been the cause.
    This was years ago and both are gone now.
    Do doctors check for these “killer cells” after a couple has had several miscarriages or are unable to conceive? Or is it up to the couple to ask for this because I’m sure there are many couples unaware of these “killer cells”
    I know I was until reading this article.
    Thank you

    • Vicki says:

      I think it depends on where you live. I know in the UK you need to have 3 miscarriages before any investigations are carried out and the friend I know who had high NK cells wasn’t offered the test for quite a while. Think she had 4 or 5 miscarriages in the end. It is very sad that lots of ladies have recurrent miscarriages and it is not investigated thoroughly enough. It is just a blood test after all and I think more and more Drs are aware of this issue now which is great. I think a few celebrities have had this issue and have brought it into the spotlight a bit more.

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