Recurrent miscarriage: causes, tests and the outlook for another pregnancy

The NHS describes a miscarriage as the loss of a pregnancy before 24 weeks. A single miscarriage is, sadly, relatively common and is usually not a sign that anything is wrong with you. The term recurrent miscarriage is reserved for people who have had three or more early miscarriages, meaning losses in the first three months of pregnancy.

The Royal College of Obstetricians and Gynaecologists (RCOG) explains that the losses do not need to follow one another consecutively, and you can have healthy pregnancies in between. Pregnancy loss in this situation is not caused by anything you did. The RCOG leaflet also makes clear that it does not cover other forms of pregnancy loss such as ectopic or molar pregnancy, which have their own information.

The RCOG says the most common cause of one miscarriage, or of recurrent miscarriage, is that the pregnancy has developed with abnormal chromosomes. It states this accounts for 1 in 2 (50%) of miscarriages and becomes more common as parents get older. In most cases this happens even though the parents themselves have normal chromosomes. In 6 in 100 couples who have experienced three miscarriages, one parent may carry their own chromosomes in an abnormal arrangement, which does not affect the parent but can cause a miscarriage if passed on.

Other factors the RCOG lists are described below.

• Age: the RCOG gives the risk of miscarriage as 11 to 15 in 100 for under 35s, 25 in 100 at 35 to 39, 51 in 100 at 40 to 44 and 93 in 100 over 45. Miscarriage may also be more common if the father is over 40.

• Ethnicity: people of Black African or Black Caribbean background are more likely to have an early miscarriage, and the reasons are not fully understood.

• Lifestyle: being overweight (BMI above 25) or underweight (BMI below 19), smoking, and drinking more than the recommended amount of alcohol or caffeine may increase the chance.

• Antiphospholipid syndrome (APS), a condition that can cause recurrent miscarriage and also increases the risk of blood clots.

• The shape of the womb: around 13 in 100 women with recurrent miscarriage have a congenital uterine anomaly, compared with 5 to 6 in 100 women generally. Fibroids or scar tissue in the womb may also play a part.

• Hormonal conditions: poorly controlled diabetes, thyroid problems such as raised TSH or thyroid antibodies, polycystic ovarian syndrome and prolactin imbalance.

The RCOG is clear on several points that people often worry about. Testing for inherited blood clotting problems (thrombophilia) is not recommended because there is no clear evidence that these cause recurrent miscarriage. It says there is no clear evidence that the immune system failing to respond normally to pregnancy is a cause, and that testing sperm is not usually offered because there is no good evidence that changing sperm health reduces the risk.

This is helpful to know because some private clinics offer wide panels of tests. Ask what the evidence is for any test you are offered, and whether the result would change your treatment.

The RCOG says you should see your healthcare professional for referral for investigations, which may be arranged in a clinic dedicated to recurrent miscarriage, and that if possible you and your partner should be seen together. It adds that it can take time to arrange the investigations or get results, and that it is up to you whether you continue trying for a pregnancy in the meantime.

Treatment depends on what is found. The RCOG describes the following. For antiphospholipid syndrome, low-dose aspirin tablets and blood-thinning injections (heparin) in pregnancy can increase the chance of a successful pregnancy, and you would be closely monitored. Routine treatment for inherited thrombophilia has not been found to improve the chance of a healthy pregnancy, although heparin may be offered in some circumstances.

If either partner has a genetic abnormality you should be offered genetic counselling, where your chances of future miscarriage and your options are explained. If you have a uterine septum you may be offered an operation to correct it, but it is unclear whether surgery for fibroids or other conditions of the womb lining reduces the risk. If you have diabetes or thyroid disease you will be supported to control it as well as possible before your next pregnancy.

The RCOG says there is no evidence that progesterone prevents recurrent miscarriage unless you experience bleeding in early pregnancy. If you have had a previous miscarriage and are bleeding in pregnancy, you should be offered progesterone. Lifestyle advice includes maintaining a healthy weight, stopping smoking, limiting caffeine to less than 200 mg a day (around two cups of tea or instant coffee) and avoiding drinking alcohol regularly or to excess.

The RCOG says it is very common for recurrent miscarriage to be unexplained. In that situation there is currently no evidence that any form of medical treatment will reduce the chance of another miscarriage. It also says the chance of a successful pregnancy next time will depend on individual circumstances but is likely to be good, even without changing anything.

The RCOG notes that supportive care from professionals experienced in recurrent miscarriage may be important in future pregnancies, and may include ultrasound scans for reassurance. Tommy's, a pregnancy charity, has developed a tool for estimating the chance of a successful pregnancy, which the RCOG points to in its leaflet.

The NHS says that a miscarriage can be difficult and upsetting and that counselling may be offered, or you can ask your GP or pregnancy unit. National charities such as Miscarriage UK and Tommy's offer information and support, and the RCOG also lists the Miscarriage Association. Support is available for partners as well.

If you become pregnant again and have bleeding, the NHS says to get urgent medical help. Call your maternity unit or early pregnancy unit, or NHS 111, for light bleeding or unusual discharge. Call 999 if you have vaginal bleeding with severe tummy pain, pain in your shoulder, feel sick, faint or dizzy, or the bleeding is heavy and soaks a period pad soon after putting it on.