- A miscarriage is the early loss of a pregnancy.
- Recurrent miscarriage is when this happens three or more times.
- Around 1 woman in every 100 has recurrent miscarriages.
- Most couples who have had recurrent miscarriages still have a good chance of a successful birth in future.
- If you have had recurrent miscarriages, you may be offered blood tests and/or a pelvic ultrasound scan to try to identify the reason for them.
- In spite of careful investigations, it is often not possible to find the reason for recurrent miscarriages.
- Your doctors will not be able to tell you for sure what will happen if you become pregnant again.
What is recurrent miscarriage?
A miscarriage is when you lose a pregnancy at some point in the first 23 weeks. When this happens three or more times doctors call this recurrent miscarriage. For women and their partners it is a very distressing problem.
Around one woman in every 100 has recurrent miscarriages. This is about three times more than you would expect to happen just by chance, so it seems that for some women there must be a specific reason for their losses. For others, however, no underlying problem can be identified; their repeated miscarriages may be due to chance alone.
Why does it happen?
Often, in spite of careful investigations, the reasons for recurrent miscarriages cannot be found. However, if you and your partner feel able to keep trying, you still have a good chance of a successful birth in future.
There are a number of things which may play a part in recurrent miscarriage. It is a complicated problem and more research is still needed.
Your age and past pregnancies
The older you are, the greater your risk of having a miscarriage. The more miscarriages you have had already, the more likely you will be to have another one.
For around three to five in every 100 women who have recurrent miscarriages, they or their partner have an abnormality on one of their chromosomes (the genetic structures within our cells that contain our DNA and the features we inherit from our parents). Although such abnormalities may cause no problem for you or your partner, they may sometimes cause problems if passed on to your baby.
Abnormalities in the embryo
An embryo is a fertilised egg . An abnormality in the embryo is the most common reason for single miscarriages. However, the more miscarriages you have, the less likely this is to be the cause of them.
It is not clear how far major irregularities in the structure of your womb can affect the risk of recurrent miscarriages. Estimates of the number of women with recurrent miscarriage who also have these irregularities range from two out of 100 to as many as 37 out of 100. Women who have serious anatomical abnormalities and do not have treatment for them seem to be more likely to miscarry or give birth early. Minor variations in the structure of your womb do not cause miscarriages.
In some women the entrance of the womb (the cervix) opens too early in the pregnancy and causes a miscarriage in the third to sixth month. This is known as having a weak (or ‘incompetent') cervix. It is overestimated as a cause of miscarriage because there is no really reliable test for it outside of pregnancy.
If you have polycystic ovaries your ovaries are slightly larger than normal ovaries and produce more small follicles than normal. This may be linked to an imbalance of hormones. Just under half of women with recurrent early miscarriages have polycystic ovaries; this is about twice the number of women in the general population.
Having polycystic ovaries is not a direct cause of recurrent miscarriage and it does not mean that you are at any greater risk of further miscarriages. We are not sure what the link is.
Prolactin is a hormone which prepares a pregnant woman's breasts to produce milk. When a woman produces too much prolactin, this is known as hyperprolactinaemia. It is not yet clear whether this condition plays a role in recurrent miscarriage because the evidence is conflicting.
If a serious infection gets into your bloodstream it may lead to a miscarriage. If you get a vaginal infection called bacterial vaginosis early in your pregnancy, it may increase the risk of having a miscarriage around the fourth to sixth month or of giving birth early. It is not clear, though, whether infections cause recurrent miscarriage.This rules out illnesses like measles, herpes, listeria, toxoplasmosis and cytomegalovirus (so you do not need to be tested for them if you have recurrent miscarriages).
Certain inherited conditions mean that your blood may be more likely to clot than is usual. These conditions are known as thrombophilia. They do not, though, mean that a serious blood clot will inevitably develop. Although thrombophilia has been thought to play some part in miscarriage, we do not yet know enough about how or why that is.
Some people have suggested that some women miscarry because their immune system does not respond to the baby in the usual way. This is known as an alloimmune reaction. There is no clear evidence to support this theory.
Diabetes and thyroid problems
Diabetes or thyroid disorders can be factors in single miscarriages. They do not cause recurrent miscarriage, as long as they are treated and kept under control.
What can be done?
Supportive antenatal care
Women who have supportive care from the beginning of a pregnancy have a better chance of a successful birth. There is some evidence having an early ultrasound scan can reduce the risk of further miscarriages.
Screening for vaginal infection
If you have had miscarriages in the fourth to sixth month of pregnancy or if you have a history of going into labour prematurely, you may be offered tests (and treatment if necessary) for an infection known as bacterial vaginosis (BV).
If you have BV, treatment with antibiotics may help to reduce the risks of losing your baby or of premature birth.
What could it mean for me in future?
Your doctors will not be able to tell you for sure what will happen if you become pregnant again. However, even if they have not found a definite reason for your miscarriages, you still have a good chance (three out of four) of a healthy birth.
Is there anything else I should know?
- You have the right to be fully informed about your health care and to share in making decisions about it.
No treatment can be guaranteed to work all the time for everyone.