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July 15th, 2006, 06:22 PM
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beck12 beck12 is offline
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Join Date: Jul 2005
Location: Michigan
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There is no single cause for recurrent miscarriages.
* Pregnancies miscarry at different times and there are different ways in which a miscarriage may occur.
* Briefly, they can be divided into several groups - genetic, hormonal, thrombophilic (blood clotting problems), anatomical (or structural), infective, and other causes.
* Many cases of recurrent mc will remain unexplained even after detailed investigations have been performed. It is important to understand that there will always be some couples whose pg losses remain unexplained. Importantly, the prognosis for a future successful pregnancy in the unexplained group is usually better than it is for couples in whom a recognised cause is identified.

In summary, no news of an abnormal test result is usually good news.

Genetic causes

* The most common cause for a single miscarriage is a chromosomal abnormality of the fetus.

Chromosomes carry genetic information. The baby inherits half of its chromosomes from the mother & half from the father. Errors in transmission or division of the chromosomes can occur & lead too many or too few chromosomes. In many of these cases, the chromosome content is so out of balance that the pg mc's. It is important to stress that these errors occur randomly & are rarely a cause of recurrent loss.

In a small percentage of couples (3-5%), one partner possesses abnormal chromosomes which they repeatedly pass on to the fetus. The most common condition is when the chromosomes, although being of the correct number, are arranged differently. This is called a balanced or reciprocal translocation and is a recognised cause of recurrent loss.

If a parental chromosome abnormality is found, referral to a Geneticist, a doctor with a special interest in this field, will normally be offered. The chances of a successful pregnancy in the future will depend on the specific type of chromosomal abnormality.


It has long been thought that a hormonal (endocrine) abnormality underlies many cases of recurrent mc. Many theories have been suggested but so far none of them have led to treatments that have improved future pg outcome.

* Low levels of progesterone hormone are often found in women whose pg's are mc'ing. However, low progesterone levels in early pg reflect the fact that the pg has not implanted successfully, rather than because the developing placenta is not producing enough progesterone to maintain the pg. This is an important point - low progesterone is the effect not the cause of the miscarriage. This explains why giving women progesterone and/or hCG hormone injections in early pregnancy does not improve pg outcome. Progesterone blood tests in early pregnancy do not help to resolve the problem.

* An u/s shows that many women with recurrent loss have PCOS - polycystic ovaries. This is a common condition (affecting 25% of all women) in which there are multiple small cysts within the ovary. These cysts aren't dangerous and can't be removed because they are within the ovary. PCOS can be associated with a number of hormonal imbalances such as increased production of LH & testosterone. A number of carefully designed studies have shown that neither PCOS nor high LH levels are a cause for recurrent loss. The effect of testosterone and other androgens on the endometrium (womb lining) are currently being studied. There are therapies for this condition. If you want to read more on PCOS:

(There is also a board here for TTC with PCOS if you have been diagnosed with this condition).

* Follicle stimulating hormone (FSH) drives the ovary to start growing follicles. Sadly some women with a history of mc are also found to have high FSH levels because their ovaries have become prematurely menopausal. Although rare, this is obviously a very important problem to identify.

* Currently the only way of determining the response of the endometrium at time of implantation is to sample it and look at the histological (microscopic) evidence of the state of the tissues. This is why you may have an endometrial (womb lining) biopsy performed towards the end of your cycle (approximately day 26). This biopsy is no more uncomfortable than undergoing a cervical smear test. However, in order to be able to obtain the most useful information from the biopsy, you will need to collect some urine samples during the earlier part of your cycle, so that your LH levels can be measured to pinpoint the exact time of O. This enables the biopsy to be more thoroughly assessed.

* Further research is being done to determine the differences in the endometrium at the time of implantation between women with recurrent mc and those whose pg's have been successful.

Thrombophilic / Blood Clotting Disorders

The importance of blood clotting disorders in causing recurrent mc has now been firmly established.

* While it has been known for a long time your blood becomes thicker in pg, it has only recently been shown that this process is more pronounced in some women compared with others. If blood clots occur in the blood vessels of the placenta the blood flow to the baby is decreased and this can lead to either mc or, if the pg proceeds, to the birth of a baby that is smaller than he/she should be.

* Antiphospholipid antibodies, the 2 most important of which are the lupus anticoagulant & the anticardiolipin antibodies, cause blood to clot more easily. Women with a history of recurrent mc who have persistently positive tests for either lupus anticoagulant and/or anticardiolipin antibodies are said to have the Primary Antiphospholipid Syndrome (PAPS).

* 15% of women with a history of recurrent mc have PAPS. In pg's in which no drug treatment is given, women with PAPS have a 90% mc rate.

* Women with PAPS have a 40% chance of a successful pg when they are treated with aspirin alone but a 70% chance when treated with aspirin & heparin (a blood thinning drug which is safe for mother & baby). Subsequent studies have confirmed this high live birth rate with aspirin and heparin and as a result this has become, both nationally and internationally, the established treatment for recurrent mc sufferers with PAPS.

* While important advances in the treatment of women with PAPS have been made, many questions remain as to whether these antibodies affect the long term health of women.

* In addition to the antiphospholipid antibodies, the role of other blood clotting abnormalities, some of which are inherited, in causing recurrent mc is being investigated. There is a new method being pioneered, Thromboelastography (TEG), to assess blood clotting. The major advantage of this method for patients is that it requires only a small blood sample and the results are rapidly available.

Infection and Recurrent MC

* The role of vaginal infections in the causation of recurrent mc is a new field. Infection may well play a role in causing late pg losses (14 wks) in a small number of women but it is unlikely to be important in causing early mcs.

It is being investigated whether there is a link between an inherited predisposition to infection and recurrent mc and whether there is an association between specific groups of bacteria found in the vagina and pg outcome.

Structural abnormalities of the uterus and Cervical Incompetence

* Until recently there has been no simple, non-invasive way to reliably diagnose abnormalities in the shape of the uterus. This has changed. 3D u/s gives clear pictures of the shape of the uterus. It is very similar to an ordinary u/s.

* Cervical incompetence is often mentioned as being a cause of mc. It only affects pregnancies that have progressed beyond 14 wks. It is most commonly diagnosed on the history of there being a painless miscarriage and the insertion of a cervical stitch (cerclage) is often recommended. There is no reliable method to diagnose cervical incompetence and in practice it is an over-diagnosed condition.


* There is some evidence that women who smoke are at increased risk of mc and that this risk is related to the number of cigarettes smoked. Similarly, women with an excessive alcohol intake are thought to be more prone to have a higher rate of mc.

Above all, remember that it is likely that your next pg will be successful.

Recent guidelines from the Department of Health suggest that all women planning to TTC should take 400 micrograms of Folic Acid before pg until approximately 12 wks gestation. This is to prevent defects such as spina bifida rather than mc itself.

Last edited by beck12; April 24th, 2009 at 09:06 PM.
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