Toxoplasmosis

Miscarriage

What is miscarriage?

Miscarriage refers to the loss of a baby during pregnancy at any stage from the date of a missed period until the 24th week of pregnancy. After 24 weeks of pregnancy, the delivery of a baby which has died in the womb is referred to as stillbirth.

How common is miscarriage?

Miscarriage is a common occurrence. Many women who miscarry may not even have known they were pregnant. One in five pregnancies will result in miscarriage. One in six pregnancies are medically recognised miscarriages, which means the pregnancy and subsequent loss was known to the woman and her health professionals. It is difficult to assess an individual's risk of miscarriage, however a study published in 1989 by Professor L Regan at her recurrent miscarriage clinic showed the percentage risk of miscarriage for a number of factors.

Relative risk of miscarriage

First pregnancy 5%

Last pregnancy a live birth 5%

Two or more previous pregnancies resulted in live birth 4%

One previous miscarriage 20%

Two previous miscarriages 28%

Three previous miscarriages 43%

It is generally accepted that around 15% of known pregnancies result in miscarriage. The rate for women under 35 years of age is around 6%, this rises to about 25% for those aged over 40. This is because the chance of chromosomal abnormality increases with the age of the woman. (See description of genetic miscarriage to follow).

Types of miscarriage

Miscarriages can occur early or late in pregnancy. Miscarriages which occur before 13 weeks of pregnancy are referred to as 'early miscarriages', the term 'late miscarriage' refers to those which occur after 13 weeks of pregnancy. Risks and causes of miscarriage are generally different depending on whether it is early or late. Miscarriage is further defined by whether it is a random, single miscarriage; or one of a number of repeated miscarriages. Recurrent miscarriage refers to the event of miscarriage more than three consecutive times.

What causes miscarriage?

Much is still unknown about why miscarriages occur. The causes of some can be identified but the reasons for many are never confirmed. There are many possible causes. Causes can be broadly divided into the following groups: genetic; hormonal; structural; resulting from blood clotting problems; or resulting from infection.

Genetic

Around 50% of early miscarriages are caused by chromosomal abnormality in the baby. Chromosomes carry the genetic information for the baby - half are donated by the father and half by the mother. Any error in the process of transmitting or dividing these chromosomes can lead to the baby becoming genetically abnormal and "incompatible with life". A miscarriage will usually result. The chance of chromosomal abnormality in the baby increases with the mother's age. A chromosomal abnormality usually causes a single, sporadic miscarriage, which means there is no need for concern in subsequent pregnancies. In a small number of cases, one partner may repeatedly pass on an abnormal chromosome and cause recurrent miscarriages. Genetic counselling may then be advisable, where couples are advised of potential issues unique to their genetic combination, and the options available to them.

Hormonal

Some miscarriages are associated with an imbalance in pregnancy hormones. Such an imbalance can lead to a number of conditions. One example is polycystic ovaries which are multiple cysts on a woman's ovaries caused by high levels of LH (luteinizing hormone) and testosterone. The presence of this condition can cause miscarriage. Another example is low levels of FSH (follicle stimulating hormone) which can cause premature menopause, and which in turn can result in miscarriage. There are other hormone related conditions which may also cause miscarriage. Various forms of treatment are available for women with hormonal imbalances.

Structural

There are some structural reasons that some women miscarry. One example is a weak cervix, which dilates too soon (known as cervical incompetence) which can lead to late miscarriage. If a woman is known to be at risk, a cervical stitch can help to prevent this. An abnormally shaped uterus is another example of a structural problem which can lead to, usually early, miscarriage. This means the baby is not able to grow healthily. A uterine septum, or divided uterus, is an example of an abnormally shaped uterus. Or large fibroids may grow in the uterus and compete for space with the baby. Surgery prior to pregnancy may help in these situations.

Blood clotting disorders

Some blood clotting disorders, like Systemic Lupus Erythematosus (SLE) or Antiphospholipid Syndrome (APS) are known to cause recurrent miscarriage. APS and SLE are rare disorders of the immune system and interfere with the body's normal blood clotting. They affect the flow of blood to the placenta and may cause clots which affect the functioning of the placenta, causing the baby to be deprived of essential oxygen and nutrients, which in turn may lead to miscarriage. These disorders might be effectively treated with aspirin and/or heparin therapy under medical supervision.

Due to infection

A number of infections can impact pregnancy. Even if the baby is not miscarried, some infections can cause damage to the baby in the womb.The role of vaginal infection as a cause of miscarriage is being investigated. It is thought that some vaginal infections may play a role in causing some late miscarriages. Some infections of the blood such as hepatitis, cytomegalovirus, human immuno-deficiency virus (HIV), rubella, and toxoplasmosis can lead to miscarriage. If the baby is not miscarried as a result of these infections, they can cause some birth defects. Food poisoning, like listeria and salmonella, can also lead to miscarriage. Again, if the baby is not miscarried these infections can cause some birth defects. Treatment of infections or diseases prior to pregnancy, and prevention of infection during pregnancy is of paramount importance. Limited treatments for some existing infections are available during pregnancy, however some of these treatments can cause damage to the unborn baby, so any use should be carefully approved and monitored by health professionals.

Other

There are a number of other general factors that contribute to an increased incidence of miscarriage. Multiple pregnancies (twins or more) are more likely to lead to miscarriage. It is thought that this could be related to increased pressure on the uterus and cervix. Or perhaps that the greater the number of babies the higher the chance of a genetic defect in one. Older women are more likely to suffer miscarriages. It is not fully understood why - experts know there is a greater chance of chromosomal abnormalities in the babies of older women, and some suggest there may also be a hormonal link. Women with poorly controlled diabetes also have a greater risk of miscarriage due to the high levels of sugar circulating in their bloodstream. Smoking also increases the chance of miscarriage. The risk associated with smoking is proportional to the number of cigarettes smoked by a woman.

What can I do to help reduce the risk of miscarriage?

It is often not possible to pinpoint the cause of a miscarriage, particularly a sporadic miscarriage. However, if there were any medical reasons or conditions which may have contributed to the miscarriage then these should be addressed by your GP/Consultant before you try for another baby. If there was no reason given for the miscarriage there are still some things you can do to get your body into the most optimum health for conception. These include; taking regular exercise, eating a healthy balanced diet, ensuring sensible working conditions, reducing stress levels, reducing alcohol consumption, stopping smoking, and taking folic acid supplements. Also, avoiding the risk of food poisoning by cooking food at high temperatures; avoiding listeria infection by not eating unpasteurised dairy products and avoiding toxoplasmosis by not eating raw meats, washing fruit and vegetables, and avoiding contact with cat faeces. For further information on these issues, please click here.