Recurrent miscarriage is diagnosed when a woman miscarries consecutively three times, before 20 weeks gestation. Some doctors, however, carry out some simple tests after two miscarriages. It is true that some women miscarry more often than chance alone would expect. When considering how common recurrent miscarriage actually is, we need to consider some numbers.
It is well known that 15% of all clinically recognised pregnancies end in miscarriage. The main cause is a problem with the gene crossover at time of conception. This is due to chance alone, and nothing can be done to prevent it. The miscarriage is nature’s way of ensuring health throughout the whole of your offspring’s life. When pregnancy is diagnosed much earlier, with very sensitive hormone tests, it is found in fact that up to 60% of pregnancies end in miscarriage – most would just present as a heavier late period if undiagnosed. So two early miscarriages is really likely to be no more than just bad luck.
Considering this figure of 15%, we would expect only 0.4% of women to miscarry three times consecutively, and it be due to nothing more than chance. In fact, 0.8-1.0% of women are recurrent miscarriers, suggesting other factors may be involved.
What is important to remember through all of this, is that 60% of women who have recurrent miscarriage (RM) will go on to have a successful pregnancy the next time – without any kind of tests or treatment. When a woman is investigated for RM, the majority of the time, no cause is found.
Causes of recurrent miscarriage
Remembering that most often no cause is found, and in 15% the happening is chance, below are some of the things which are thought to be associated with RM:
- General disease – e.g. Systemic Lupus Erythematosus (SLE) which is a disease affecting many systems of the body. People affected often have a butterfly-rash over the cheeks and bridge of the nose.
- Antiphospholipid antibody syndrome – this is an immune disease where the main problems are RM, clots in the veins or arteries and often a low count of one of the blood components, the platelets. If pregnancy is successful, it can be complicated by poor growth of the baby and a disease of pregnancy called preeclampsia.
- Chromosome problems – i.e. Mum & Dad are fine, but when put together an unusual mismatch occurs (only three percent of RM)
- Uterine (womb) abnormality – e.g. double-womb or a septum down the middle (only one and three percent of RM)
- Fibroids – whorls of normal uterus tissue growing in the muscle, sometimes causing mis-shaping of the womb cavity.
- Cervical incompetence (weakness) – may cause miscarriage in 2nd trimester. Only likely to be a cause if there is clear history of severe trauma to the cervix (not, for example, just a D&C or cone biopsy) with RM.
- Polycystic ovary syndrome – often this disease causes infertility or trouble even getting pregnant. It has also been found when this is present with a raised hormone level (LH) there is an increased risk of miscarriage. Hormonal treatment for this is being looked into presently, but there is little evidence available at the moment on whom, if anyone, would definitely benefit from treatment.
- Immune problems – couples with RM may have some similar components of the immune system. This can make it difficult for Mum to make the appropriate response to pregnancy. This is unusual, and no immune therapy has been found to improve chances above and over the 60% seen without intervention.
- Hormone ‘deficiency’ – in pregnancies which end in miscarriage, sometimes the levels of a hormone called progesterone are found to be low. This is thought to reflect an early pregnancy failure, and is probably the RESULT rather than the cause of the miscarriage. Certainly progesterone supplements do not increase the likelihood of an ongoing pregnancy.
Things unlikely to cause recurrent miscarriage
- Retroversion – or backward tilting of the uterus.
- Infection – such as toxoplasmosis, listeria, brucella, chlamydia, herpes simplex and cytomegalovirus.
- Endocrine or metabolic disease – hypothyroidism (underactive thyroid), diabetes mellitus, Crohn’s disease, sickle cell or endometriosis.
- Occupational exposures – very little reliable evidence exists for things such as herbicide spraying, electromagnetic fields, chemical inhalation, anaesthetic gases or VDU usage.
- Not resting enough – bedrest doesn’t alter whether you miscarry or not. Nor does working when you’re pregnant, exercise, making love or flying.
The investigations the doctor will do
Obviously the doctor will want to take a full history and examination looking for signs of the things mentioned above. Blood tests are taken to look for hormone irregularities or polycystic ovary disease (PCOD), SLE and antiphospholipid syndrome (lupus anticoagulant and anticardiolipin antibodies). Both partners should be checked for a chromosome (genetic) problem. An ultrasound scan may indicate the presence of PCOD. A hysteroscopy involves a tiny telescope look into the womb cavity to check for the presence of abnormalities or fibroids. It is usually done under a general anaesthetic, but can be done under local too.
The treatment for miscarriage
If any of the above tests should come back indicating an underlying reason for the problem, then treatment is directed at the cause – e.g. genetic counselling, removal of fibroids, cervical stitch. If all of the above have been excluded (as they will do in most cases), the diagnosis is recurrent miscarriage of unknown cause. The only intervention to have demonstrated benefit is serial ultrasound scans in the early months of pregnancy. It is certainly not unreasonable to expect this psychological support to improve outcome given the close interaction between the higher areas of the mind and the delicately balanced hormonal system.
Progesterone supplements have been evaluated in clinical trials and have not been shown to be of any benefit. A few people still use them, but it must be realised that they are not any better than placebo. There will be the cases who had miscarriage three times then went on to deliver the following two times with progesterone supplements – most doctors certainly wouldn’t deny the treatment again, but the fact remains that properly conducted studies (as opposed to anecdotal reports) have not found them to be of benefit.
Above all, remember that 60% of women will have a successful pregnancy the next time. It’s difficult to face another disappointment when one has been hurt so much, but most women who persist do have a successful pregnancy eventually.
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