Recurrent Miscarriage
Approximately 1 in 5 pregnancies are lost before viability and this is termed a miscarriage. In fact if you speak to any woman who has at least one child, most of them would have suffered a miscarriage at some time. It is often one of those devastating events that remains a secret.
When should I get investigated?
Concern is heightened when a woman suffers with recurrent miscarriage and it is reasonable to proceed with clinical evaluation following two consecutive losses in the first trimester. In the vast majority of couples, no cause is found and this can be quite frustrating.
It is generally accepted that lifestyle factors contribute little to recurrent miscarriage, however epidemiological studies have linked certain lifestyle factors to miscarriage. Overweight and obesity, excessive daily caffeine consumption (>3 cups of coffee per day) and psychological stress have all been associated with higher miscarriage rates. Although investigations often yield ‘no abnormalities’, causes identified can often be treated with great success so it is very reasonable for any couple with recurrent miscarriage to seek assistance and advice after 2 or more consecutive miscarriages.
Is there a link between Natural Killer Cells and Miscarriage?
What do “Natural Killer Cells’ do to cause miscarriage exactly?
Pregnancy is unique in that the mother’s immune system must allow a ‘foreign body’ to invade the lining of the womb. What is speculated to happen in recurrent miscarriage is that high uterine Natural Killer Cell activity impacts implantation and either does not allow this invasion to take place (implantation failure) or causes poor implantation and ultimately a miscarriage. This theory remains unproven.
How can I be tested for uterine Natural Killer Cells (uNKCs)?
This is done by taking a sample of the lining of the womb and sending it to a pathology laboratory for analysis. This can be done whilst awake and is similar to having a pap smear, though a little more uncomfortable. Another option is to undergo a procedure called hysteroscopy and curette where a sample of the lining is collected whilst under a general anaesthesia. It is suggested that a blood test for peripheral NKCs can be taken – however there is no proven relationship between peripheral NKCs and uterine NKCs – so this is not the best test to do.
When you have experienced a miscarriage or multiple miscarriages, my role as a fertility specialist is to nurture part of your emotional processes, and supporting you with clear communication about every step of the fertility journey. Quite often, it includes listening to how you or your partner feel about these 'rollercoaster moments', from hope to insecurity, from disappointment to a next step. It is a deeply human experience, and my role is to be a partner on your journey, beyond my specialised medical experience. That is what I call a holistic approach to fertility treatment.
What does research have to say about this topic?
This is a very controversial area of reproductive medicine. While there have been countless studies undertaken on this subject they have yet to prove conclusive. It is not known whether peripheral NKCs (in the bloodstream) represent the same population as uterine NKCs. It is also unproven that high uNKCs actually cause recurrent miscarriage – only that they are associated with recurrent miscarriage. Additionally the treatments suggested for high uNKCs in women with recurrent miscarriage are also controversial with some studies showing they work and some showing they don’t.
It doesn’t seem to be very clear cut!
The absence of clear studies and proven data does leave some gaps in this particular topic which is why it’s important to speak to fertility experts. While NKCs may be responsible for infertility problems and repeat miscarriages there are many other reasons why these things occur. Treatments should be individualised to each specific case.
Useful links
Want to know more about miscarriages? Read my blog post or watch the video.
Dr Hunter
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