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Innermost Secrets / Innermost Living / Body Clock
Skip Navigation LinksNatural Killer Cells (NK Cells)
Page modified at: 28/08/2011

Natural Killer CellsNatural Killer Cells and Recurrent Miscarriage

Previous research has shown that there are increased numbers of immune cells called natural killer (NK) cells in the lining (endometrium) of the wombs of women who suffer from recurrent miscarriages - when three or more pregnancies fail to go to term. The condition affects two in every 100 women of reproductive age. In half of cases, no obvious cause will be found and in a third of those, abnormally high numbers of NK cells are found in the womb lining.

The cells should make up no more than 5% of all those in the lining. Dr Siobhan Quenby and colleagues at the Liverpool Women's Hospital believe the NK cells might attack the growing embryo and stop it from implanting properly in the womb, leading to miscarriage. The cells have steroid hormone receptors on their surface, which led the researchers to question whether giving susceptible women steroid drugs might help prevent miscarriage.

The steroid is thought to quash an abnormal immune reaction.Taking steroid tablets while trying to conceive could reduce the risk of miscarriage for some women, scientists at Liverpool University suggest. Doctors there have already helped some women with histories of recurrent miscarriages to have healthy babies. The steroid is thought to work by blocking immune cells that, in some women, appear to go into overdrive in the womb and stop embryos implanting.


Published Research

In her research study, Dr Quenby recruited 110 women who had severe recurrent miscarriage. They had experienced an average of six miscarriages with no known cause. The researchers took samples of the women's womb linings and tested them to identify the quantity of NK cells. Any women whose endometrial cells contained more than the normal range were offered 20mg of the oral steroid prednisolone for 21 days from the start of their menstrual cycle. Out of a possible 33 women, 29 agreed to take the drug. When the researchers took a second endometrial sample after the 21 days of prednisolone treatment, they found the steroid had significantly reduced the percentage of NK cells in the womb lining.

Dr Quenby told the 21st annual conference of the European Society of Human Reproduction and Embryology in Copenhagen, Denmark: "The women had an average of 14% before treatment, with the highest percentage being 72%, and after treatment the average dropped to 9%."


Testing for NK Cells at Innermost Secrets

The test for high NK counts is based on an endometrial biosy at about day 21-23 of the menstrual cycle. Results are available in 2-3 weeks. The sample will be taken in a similar manner to taking a cervical smear. You may experience some mild discomfort whilst the biopsy is being taken. The risk of any damage to your womb during the procedure is absolutely minimal and if any damage should occur it will heal spontaneously. If we took the biopsy whilst you are pregnant, it could possibly cause a miscarriage but the risk is very small. Therefore, you need to use barrier method of contraception in the month that you have your biopsy (for example use condoms). The biopsy will be analysed for the NK cells and various other cells that line your womb. Women with recurrent miscarriage have up to a 30% chance of having high levels of NK cells.


Treatment for High Counts of NK Cells at Innermost Secrets

For those with a high count of NK cells, our current treatment protocol is based on a daily dose of 20mg Prednsioone from day 2 of each cycle until week thirteen of pregnancy. The doe is gradually reduced by 5mg every 1-2 days in the 12th week.


Risks and Side Effects of Treatment

You may experience minor side effects of steroids such as mood changes, weight gain, increased appetite, indigestion, high blood pressure and high blood sugar levels and a rare complication called avascular necrosis (This causes severe pains on your hip joint). The prednisolone is thought to cause the developing fetus very little harm. However, there is some evidence to suggest that it could be associated with cleft lip and poor growth in the uterus.