Most women go on to have a healthy pregnancy after a miscarriage, so tests are not usually offered until a woman has recurrent miscarriages or 1 late miscarriage. This policy can seem frustrating. You’ve been through a traumatic experience and it is completely understandable to want to know why it happened. The reason for the policy is because most women who have 1 or 2 miscarriages will go on to have successful pregnancies.
However, some specialists may see women after 2 miscarriages in a row. It is worth talking to your GP to find out whether you can be referred for tests.
Blood tests can be used to check for blood clotting disorders such as antiphospholipid syndrome (APS) and thrombophilia.
Chromosomes are genetic structures in our cells that contain our DNA and the features we inherit from our parents. If your baby had abnormal chromosomes (see below), doctors may do some blood tests to check your and your partner’s chromosomes for abnormalities.
Testing the baby
You should be offered tests to check for abnormalities in your baby’s chromosomes. This is not always possible but may help doctors find out your chances of miscarrying again.
If you have had a late miscarriage, you may also be offered a post-mortem examination of your baby. This will not happen without your permission (consent). Find out more about what happens to your baby after miscarriage.
Tests to look at the shape of your womb
If you have recurrent miscarriages, you should be offered a pelvic ultrasound scan to check for any abnormalities in the shape of your uterus. You’ll be offered more tests if your doctors think there may be a problem.
Find out more about uterine abnormality.
Tests for infection
If you have had a late miscarriage, you may have blood tests and vaginal swabs to test for an infection.
Where do I have these tests?
The tests are normally done when you are referred to the recurrent miscarriage clinic. Any tests that need to be done at the time of the miscarriage will be done at the Early Pregnancy Unit or hospital.
What are Natural Killer Cells?
Natural killer cells (NK cells) form part of the body’s immune system. They help the body fight infection and cancer. Every organ has NK cells to protect it, including the uterus (womb).
NK cells in the uterus are known as uNK cells. They play an important role in helping the body become pregnant.
In order to become pregnant, the womb lining needs to inflame slightly so the embryo can attach (or implant) to the uterine wall. uNK cells contribute to this process of inflammation. If there are too many or too few uNK cells, this can cause too much or not enough inflammation, which are both associated with infertility and miscarriage.
uNK cells also help blood vessels to develop, which make sure that the baby gets a good supply of oxygen and nutrients during pregnancy.
It is possible to have tests to measure your level of NK cells. If you do decide to go ahead with tests or treatment, please be aware that the treatment is still considered experimental. Although there is a series of scientific studies that find that NK cells are important for normal pregnancy, it’s still not clear what the optimal level of uNK cells is and what is the best way to correct any imbalance. This is still yet to be tested in large scale studies.
Can I get tested to check the level of my NK cells?
It is possible to have tests to measure your level of NK cells. However, it is not available on the NHS. Some fertility clinics offer tests, but not all. If they do, you will have to pay for it. This can be expensive and will vary from clinic to clinic.
Before deciding whether or not to have tests, it’s important to know that there are some issues with these tests:
- There is a lack of evidence about the exact role that NK cells have in causing miscarriage.
- There are no official guidelines for what ‘normal’ NK cell activity is.
- It is difficult to measure the ideal level of NK cells and when an imbalance can cause infertility and miscarriage.
- Specialists have different opinions about how to do these tests and report the results – as there are no official guidelines, doctors will interpret the results based on their clinic’s ‘normal’ range and their clinical and professional experience.
- The level of uNK cells is different in each menstrual cycle so having a single test may not give a clear picture.
Testing may involve peripheral NK cell testing. This is a blood test that measures the percentage and quantity of NK cells in the bloodstream. However, these cells are different to uNK cells. Therefore, some clinics do uNK testing, which is similar to an endometrial scratch. This involves scratching the lining of the womb (the endometrium) to test the tissue for NK cell activity.
Is there treatment for abnormal levels of NK cells?
Treatment for abnormal NK cells is usually aimed at suppressing the number and activity of the uNK cells. The problem with this approach is that having too few or too many uNK cells have both been associated with recurrent miscarriage. Treatment for abnormal NK cells includes medications that are often used to treat conditions that affect the immune system (known as autoimmune diseases). This includes prednisone, which is a steroid commonly used for asthma and arthritis.
Intravenous immunoglobulin (IVIg) may also be given intravenously during pregnancy. This means it is given by a drip into the vein. Immunoglobulins are proteins produced naturally by the body's immune system to fight off infections.
It’s important to know that the Royal College of Obstetricians and Gynaecologists (RCOG) says that there is not enough evidence that these treatments are effective. These medications can also have serious side effects in pregnancy. For example, prednisolone can affect the baby’s growth in the womb.
Who can I talk to about NK cells?
You can talk to your doctor about NK cells to find out more. They can give you their professional opinion about whether testing and treatment may help you. Doctors in different clinics may have different opinions.Hide details
Treatments for antiphospholipid syndrome (APS)
If you have APS, you may be treated with low-dose aspirin tablets and heparin injections during your next pregnancy. These medications make your blood less likely to clot and are safe to take in pregnancy.
Having APS means you are at increased risk of complications during pregnancy, such as:
You should be carefully monitored so that you can be offered treatment for any problems that come up.
Treatment for thrombophilia
If you have thrombophilia and have had a miscarriage between 12 and 24 weeks of pregnancy, you should be offered treatment with heparin and aspirin.
Referral for genetic counselling
If either you or your partner has a chromosome abnormality, you should be offered the chance to see a specialist called a clinical geneticist. They will discuss with you what your chances are for future pregnancies and will explain what your choices are. This is known as genetic counselling.
Find out more about conception and your baby’s genes.
Monitoring and treatment for a weak cervix
If you have had a miscarriage between 14 and 24 weeks and have been diagnosed with a weak cervix (cervical incompetence), you may be offered an operation to put a stitch in your cervix during your next pregnancy. This is usually done through the vagina at 13 or 14 weeks of pregnancy under a general or spinal anaesthetic.
If it is unclear whether your late miscarriage was caused by a weak cervix, you may be offered vaginal ultrasound scans during your pregnancy to measure the length of your cervix. This may give information on how likely you are to miscarry. If your cervix is shorter than it should be before 24 weeks of pregnancy, you may be offered an operation to put a stitch in your cervix.
Find out more about cervical incompetence.
Surgery to the uterus
You may be offered surgery if you have a uterine abnormality although the effectiveness of this surgery is not well known.
You may be offered progesterone or human chorionic gonadotrophin hormones early in pregnancy to prevent recurrent miscarriage.
What happens next?
Your doctor will talk to you about your test results and what this tells them about your chances of having another miscarriage and successful pregnancy.
Even if you do have some tests, it’s important to know that doctors may not be able to find a reason why you’ve miscarried. This can be very distressing, but try not to worry too much if this is the case. Most couples are likely to have a successful pregnancy in the future, particularly if test results are normal.
Going through the process of having these tests can be stressful. Tommy’s is here to help you. You can talk to a Tommy’s midwife for free, Monday-Friday, 9am-5pm. You can call them on 0800 0147 800 or email [email protected]. All our midwives will be able to talk to you about what you’re going through.
Find out more about what other support is available.
Tommy’s is funding the cost of the UK’s first national Miscarriage Research Centre and aims to halve the number of miscarriages by 2030 by funding medical research.
1 in 4 pregnancies end in loss or preterm birth – and most parents never find out the real reason why. Our research is dedicated to finding out why miscarriages happen and how to prevent it in the future.
Find out more about our Tell Me Why campaign.
Expectant management is one of 3 treatment options you can have if you have a missed or incomplete miscarriage.
Surgical management is one of 3 treatment options you can have if you have a missed or incomplete miscarriage.
If you have a missed or incomplete miscarriage, you may be offered medicine to help the miscarriage move along.
Your treatment for miscarriage will depend on the type of miscarriage you have.
A late miscarriage may be treated differently to early miscarriages.
Brighton, P et al (2017) Clearance of senescent decidual cells by uterine natural killer cells in cycling human endometrium. eLife
Clinical Knowledge Summaries. Miscarriage https://cks.nice.org.uk/miscarriage (Page last reviewed: May 2018 Next review due: December 2023)
Royal College of Obstetricians & Gynaecologists (2016) Early miscarriage https://www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/pi-early-miscarriage.pdf
Royal College of Obstetricians & Gynaecologists (2012) Recurrent and late miscarriage: tests and treatment of couples https://www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/pi-recurrent-and-late-miscarriage---tests-and-treatment-of-couples.pdf
Royal College of Obstetricians & Gynaecologists (2016) The Role of Natural Killer Cells in Human Fertility https://www.rcog.org.uk/globalassets/documents/guidelines/scientific-impact-papers/sip_53.pdf
Brighton, P et al (2017) Clearance of senescent decidual cells by uterine natural killer cells in cycling human endometrium. eLife https://elifesciences.org/articles/31274
Lucas, ES, Vrljicak, P., Muter, J et al (2020) Recurrentl pregnancy loss is associated with a pro-senescent decidual response during the peri-implantation window. Communications Biology 3, 37 (2020) https://www.nature.com/articles/s42003-020-0763-1Hide details
ℹLast reviewed on April 16th, 2020. Next review date April 16th, 2023.