What is recurrent miscarriage?
Recurrent miscarriage is defined as the loss of three or more consecutive pregnancies. It affects 1% of couples trying to conceive. Sometimes a treatable cause can be found, and sometimes not. Regardless of the cause, most couples are more likely to have a successful pregnancy next time.
What are the risk factors?
Maternal age and number of previous miscarriages are two independent risk factors for a further miscarriage. The risk of miscarriage is highest among couples where the woman is ≥35 years of age and the man ≥40 years of age. Each new pregnancy loss increases the risk of a further miscarriage. But even after three miscarriages, most couples will have healthy pregnancy next time. Being very underweight or overweight may also increase your risk.
Antiphospholipid syndrome (APS): This blood clotting problem is the most important treatable cause of recurrent miscarriage. It happens when your immune system forms abnormal antibodies that attack fats called phospholipids in your blood. This makes the blood more ‘sticky’ and likely to clot, which is why APS is sometimes called ‘sticky blood syndrome’.
Abnormal chromosomes: In couples with recurrent miscarriage, chromosomal abnormalities of the embryo account for 30–57% of further miscarriages. The risk of miscarriage resulting from chromosomal abnormalities of the embryo increases with advancing maternal age. Much less commonly (in less than five in one hundred couples with recurrent miscarriage), one partner carries a chromosomal defect called a ‘balanced translocation’. This doesn’t cause a problem for the parent, but it can be passed on to the baby as an ‘unbalanced translocation’. This means that some genetic information is duplicated and some is missing.
Other blood clotting problems, Inherited thrombophilic defects:
Both inherited and acquired thrombophilias, including activated protein C resistance (most commonly due to factor V Leiden mutation), deficiencies of protein C/S and antithrombin III ,hyperhomocysteinaemia and prothrombin gene mutation, are established causes of systemic thrombosis. In addition, inherited thrombophilias have been implicated as a possible cause in recurrent miscarriage and late pregnancy complications with the presumed mechanism being thrombosis of the uteroplacental circulation.
Cervical weakness: This is a known cause of late (second trimester) miscarriage.
Possible causes: The problems listed below may play a part in causing recurrent miscarriage, but the scientific evidence isn’t strong enough to say this for sure.
Endocrine factors like uncontrolled Diabetes and Thyroid disorders can cause sporadic miscarriages but they are not thought to cause recurrent miscarriages
Abnormally-shaped uterus Some miscarriages, particularly late ones, are thought to happen because the uterus (womb) has an abnormal shape.
Polycystic ovary syndrome (PCOS) The increased risk of miscarriage in women with PCOS has been recently attributed to insulin resistance, hyperinsulinemia and hyperandrogenaemia.
Infection Some serious infections can cause or increase the risk of single miscarriages. These include toxoplasmosis, rubella, listeria and genital infection. But it is not clear whether infection plays a role in recurrent miscarriage.
Immune problems Raised levels of uterine NK (uNK) cells may increase the risk of recurrent miscarriage, but more research is needed to prove this.
What are the recommended tests and treatments?
Antiphospholipid syndrome (APS) testing: You will be offered blood tests for APS after three or more early miscarriages or one or more late ones. To get a clear diagnosis you must test positive on two separate occasions for one of the antiphospholipid antibodies. These are known as ‘lupus anticoagulant’ and ‘anticardiolipin’ antibodies.
Treatment: If you do have APS you will probably be treated with low dose aspirin and heparin injections. This combination has been shown to improve your chance of having a live baby.
The aspirin treatment (75 mg daily) will start early in pregnancy, when you have a positive pregnancy test. The heparin injections are usually started once the baby’s heartbeat has been seen on a scan. If you have this treatment, you will be monitored carefully throughout your next pregnancy as APS can cause other problems for you and your baby.
Tests for other blood clotting problems: You may be offered blood tests for inherited clotting disorders called ‘thrombophilias’.
Treatment: If tests show you have one of these disorders you may be offered heparin injections in your next pregnancy. If you had a late miscarriage before, this treatment may improve your chance of having a live baby.
Test for Genetic problems: The tissues from the third miscarriage are sent to the lab to test for abnormalities in the baby’s chromosomes. But this may be difficult to arrange if you didn’t miscarry in hospital. If tests on the miscarriage tissue show chromosomal abnormalities, that usually means that this is a ‘one-off’ problem and you have a good chance that you will have a healthy pregnancy next time.
If the result shows that the baby has an ‘unbalanced translocation’, you and your partner will be offered blood tests to show whether one of you carries the chromosomal problem called a ‘balanced translocation’. It can take up to six weeks to get a result.
Treatment: There is no treatment, If you or your partner are found to carry a balanced translocation. You will be offered special genetic counselling which will help you to decide about future pregnancies.
Abnormally-shaped uterus: All women with recurrent first-trimester miscarriage and all women with one or more second-trimester miscarriages are offered a pelvic ultrasound to assess uterine anatomy.
Suspected uterine anomalies may require further investigations to confirm the diagnosis, using hysteroscopy, laparoscopy or three-dimensional pelvic ultrasound.
Cervical weakness: Cervical weakness can be hard to diagnose and there is no reliable test outside of pregnancy.
Treatment: If you have had a late miscarriage and there is a suggestion that it might be due to cervical weakness, you may be offered regular scans of your cervix in your next pregnancy. Some women are treated with a ‘cervical stitch’.
Other tests and treatments: Few other tests and treatments may be offered, however there is insufficient evidence for their routine use.
Unexplained recurrent miscarriage: More than half of the couples who have investigations for recurrent miscarriage don’t come out with an answer as to why they have miscarried. If this happens to you, you might be very disappointed. You can be reassured that this is actually good news as women with unexplained recurrent miscarriage have an excellent prognosis for future pregnancy outcome without pharmacological intervention.