Updated 22 May 2015


A miscarriage is the loss of the products of conception before viability.



  • A miscarriage is defined as loss of the products of conception before viability
  • About 15% of pregnancies are lost in the first three months.
  • More than half the miscarriages in the first 13 weeks of pregnancy are caused by chromosomal problems in the foetus
  • Miscarriages after the third month are generally due to illness or other problems with the mother

What is a miscarriage?

A miscarriage, also known as a spontaneous abortion, is defined as loss of the products of conception before viability. The products of conception are the foetus, placenta and amniotic fluid. Viability refers to the baby being able to survive after delivery. This point is at approximately 26 weeks of gestation. Normally pregnancy lasts for 40 weeks.

There are different types of miscarriage:

Threatened miscarriage

This refers to bleeding in early pregnancy associated with little or no pain. At this stage the mouth of the womb or cervix is still closed. It is important to note that most of these women will not abort.

Inevitable miscarriage

In this case the threatened miscarriage has progressed. The woman now experiences cramping pain in the back and lower abdomen. Clots are often passed as the mouth of the womb is open and the contents will be lost. Attempts to save the pregnancy at this stage are usually futile.

Recurrent miscarriage

This distressing problem affects a very small number of couples. Medical investigations are usually started after a third consecutive loss, but some doctors will investigate earlier. This is because the chances of another failed pregnancy increase significantly after two losses.

Missed miscarriage

When the foetus has died inside the womb but not been expelled, a missed miscarriage has occurred. In this case the womb will fail to enlarge and the signs of life such as the foetal heartbeat will disappear.

Septic miscarriage

Should the contents of the uterus become infected before, during or after an abortion, a septic miscarriage has occurred. This is common during unsafe abortions.

What causes miscarriage?

  • More than half of all miscarriages during the first 13 weeks of pregnancy are caused by problems in the foetus' chromosomes. Chromosomes are tiny structures inside body cells that carry the genetic material. Each chromosome contains genes that determine a person's appearance, sex, and blood type. Problems in the number or structure of the chromosomes or the genes can lead to miscarriage. Frequently this is nature's way of ending a pregnancy in which the foetus was not developing normally.
  • Most chromosomal problems occur by chance and are not likely to recur in later pregnancies. In a small number of cases, however, chromosomal problems can cause recurrent miscarriages. In such cases, a karyotype to examine the chromosomal structure should be performed on the parents.
  • Certain abnormalities of the womb (uterus), which are linked to miscarriage, can be treated surgically. A special X-ray (hysterosalpingogram) or direct visualisation through a lens (hysteroscope) can detect abnormalities of the uterine cavity, and an endometrial biopsy may provide information about the uterine lining, where implantation occurs.
  • In some cases, illnesses of the mother will lead to miscarriage. Systemic lupus erythematosus, congenital heart disease, severe kidney disease, high blood pressure, uncontrolled diabetes, thyroid disease or an intrauterine infection can all interfere with the pregnancy. When these illnesses are treated, the chances for a successful pregnancy improve. Such illnesses thus require close monitoring during pregnancy.
  • Disorders of the immune system can also lead to miscarriage. The immune system defends the body against damage by recognising and attacking foreign substances. The mother's immune system will not normally attack her foetus. Sometimes, however, this protection may be lost. Problems in the immune system can be diagnosed by blood tests.
  • Hormone imbalance may also lead to repeated miscarriage. The hormone progesterone prepares the lining of the uterus for the fertilised egg during the second half of the menstrual cycle. When an egg is fertilised, this hormone continues to prepare the uterine lining for the embryo. Enough progesterone must be produced to maintain the pregnancy, otherwise miscarriage will occur. If tests indicate that a woman's body is not producing enough progesterone, supplements can be prescribed to correct the problem.
  • In some cases environmental and lifestyle factors lead to greater risk of miscarriage. Women who smoke, drink heavily or use illegal drugs, especially cocaine, increase their risk of miscarriage. Exposure to high levels of radiation or toxic substances may also be factors in recurrent miscarriages.

Who suffers miscarriage and who is at risk?

Spontaneous miscarriage is common with about 15% of pregnancies being lost in the first three months.

Miscarriages during the first three months tend to be due to problems with the foetus. Miscarriages occurring in the second three-month period of pregnancy tend to be related to problems with the mother.

What are the symptoms and signs of miscarriage?

The main symptoms are pain in the lower abdomen and bleeding from the vagina. In an inevitable abortion, the cramping pain and bleeding may be severe.

During the physical examination the doctor will determine whether the mouth of the womb (cervix) is open. If it is, then the patient is probably experiencing an inevitable abortion. If the mouth of the womb is still closed, then a threatened miscarriage is the likely diagnosis.

How is a miscarriage diagnosed?

The clinical history of pain and bleeding, and a physical examination are usually sufficient to make the diagnosis.

An ultrasound may be used to examine the contents of the womb, checking for an empty sac or signs of life in a foetus. It can also be used to see if all the products of conception have been passed.

Can a miscarriage be prevented?

Unfortunately, once a miscarriage has become inevitable, attempts to save it are usually futile. Research has shown, however, that taking vitamins before and during pregnancy may lower the risk of miscarriage.

How is a miscarriage treated?

This depends on the type of miscarriage. Although bed rest is usually prescribed for a threatened miscarriage, this has not been proven to be effective. The patient is encouraged not to work and to stay off her feet at home. Women are often told to avoid intercourse for a while. Although there is not much evidence that this is harmful, many people suffer guilt feelings if a miscarriage occurs after intercourse.

In any case where non-viable products of conception remain in the womb, they must be removed to prevent further bleeding and infection. This used to be known as D&C (dilation and curettage) but currently, the common practice is to empty the womb by manual vacuum aspiration when necessary. If the womb is already empty, careful monitoring may be all that is required.

Septic abortion must be treated with intravenous antibiotics and early emptying of the womb. This condition can be life-threatening.

Since many women suffer psychological problems as a result of miscarriage, counselling and support are important aspects of treatment and must not be overlooked.

When to see your doctor

If you are pregnant and suffer from:
  • Pain or cramping
  • Bleeding
  • What appears to be a normal period after a diagnosis of pregnancy

(Reviewed by Dr P.S. Steyn, Head, Tygerberg Hospital and Stellenbosch University)

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