Recurrent Miscarriage

 

Miscarriage is the commonest complication of pregnancy. Approximately 15% of all pregnancies end in a miscarriage and 25% of women who become pregnant will experience.

Women who have had a miscarriage may be divided into 2 groups.

• Those who have suffered a single, sporadic miscarriage.
  

• Those who repeatedly miscarry.

This is usually defined as the loss of 3 or more consecutive pregnancies. Only 1% of couples fall into this group.

This division is important in predicting the chance of a successful pregnancy in the future, and the likelihood of there being a recurring cause for the loss of the pregnancy. A woman in the first group has an 80% chance and a woman in the second group a 60% chance of her next pregnancy being successful.

What Causes Recurrent Miscarriage?

There is no single cause for recurrent miscarriages.

Pregnancies miscarry at different times and there are different ways in which a miscarriage may occur.

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

The chromosomes carry the genetic information and he fetus inherits one half of its chromosomes from the mother and one half from the father.

Errors in the transmission and the division of the transmission and the division of the chromosomes can occur and lead to the fetus having either too many or too few chromosomes. In many of these cases, the chromosome content is incompatible with life and the pregnancy miscarries.

It is important to stress that these errors occur randomly and are not a recurring cause of the miscarriage. In a small number of couples, between 3 and 5% , one partner may themselves have abnormal chromosomes.

The most common condition is when the chromosomes although being of the correct number are arranged differently. This is a recognized cause of recurrent miscarriages.

If this is found to be the case referral to a Geneticist, a person with a special interest in this field, is made. The chances of a successful pregnancy in the future will depend on the exact nature of the chromosomal abnormality.

Blood Clotting Disorders

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

Whilst it has been known for a considerable time that a woman's blood becomes thicker
in pregnancy, it has only recently been established that this process 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 miscarriage or, if the pregnancy proceeds, to the birth of a baby that is smaller than he or she ought to be.

Antophospholipid antibodies, a family of antibodies the two most important of which are the lupus anticoagulant and the anticardiolipin antibodies, cause blood to clot more easily.

Women with a history of recurrent miscarriage who have persistently positive teats for either lupus anticoagulant and/or anticardiolipin antibodies are said to have the Primary Antiphospholipid Syndrome.

We have reported that 15% of women with a history of recurrent miscarriage have persistently positive tests for antiphospholipid antibodies. In pregnancies in which no drug treatment is given these women have a 90% miscarriage rate. We have recently completed a treatment trial comparing the success rate of aspirin versus aspirin and heparin (an anti-clotting drug) in the treatment of women with the Primary Antiphospholipid Syndrome.

This trial showed that treatment with aspirin alone has a success rate of 40% compared with a 70% success rate with aspirin and heparin. In addition to the antiphospholipid antibodies we are investigating the role of other blood clotting abnormalities in causing recurrent miscarriage.

HORMONES
It has long been thought that a hormonal (endocrine)abnormality underlies many cases of recurrent miscarriage.

The most common endocrine abnormality found in women with recurrent miscarriage is over secretion of the hormone known as Luteinising Hormone (LH).

What does the Luteinising Hormone do?
This hormone is produced by the pituitary gland, which is in the brain, and acts on the ovary to cause the egg to mature and to be released (ovulation).

Overproduction of LH most commonly occurs in women who have polycystic ovaries (PCO), a condition in which there are multiple small cysts within the ovary. This condition can be diagnosed on ultrasound scan and is found in 60% of women who repeatedly miscarry.

Just over one half of women with PCO are found to produce too much LH. We have recently reported that women who produce too much LH have an excellent chance of a successful pregnancy next time when give supportive care alone and that suppressing the levels of LH has no additional benefit.

We are currently carrying out further research aimed at determining the association between PCO and recurrent miscarriage.


Infection and Recurrent Miscarriage
Another area we are actively investigating the relationship between infection and recurrent miscarriage. In particular, whether there is a link between an inherited predisposition to infection and recurrent miscarriage and whether there is an association between specific groups of bacteria found in the vagina and pregnancy outcome.

The role of vaginal infections in the causation of recurrent miscarriage is a new field that is beginning to be investigated. Infection may well play a role in causing late pregnancy losses.(14 weeks gestation) in a small number of women but it is unlikely to be important in causing early miscarriages.

Cervical Incompetence.

Cervical incompetence is often mentioned as being a cause of miscarriage.

It only affects pregnancies that have progressed beyond 14 weeks gestation.
It is most commonly diagnosed on the history of there being a painless miscarriage and the insertion of a cervical stitch is often recommended. There is no reliable method to diagnose cervical incompetence and in practice it is an over-diagnosed condition.

General
It has been estimated that up to 10% of women who miscarry repeatedly have an abnormal shaped uterus. However, the proportion of such women in the population is unknown and it is likely that the majority of women with a uterine abnormality have a normal pregnancy.

There is some evidence that women who smoke are at increased risk of miscarriage and that this 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 miscarriage. Recent research shows that there is no association between the use of video display units (VDUs) and miscarriage.

Further studies are awaited. Identification and treatment of the recognised causes of miscarriage are important to increase your chances of a successful pregnancy in the future. The Recurrent Miscarriage Clinic also offers support and information which we believe is equally important.

Identification and treatment of the recognised causses of miscarriage are important to increase your chances of a successful pregnancy in the future.
Above all, remember that it is likely that your next pregnancy will be successful.

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