Miscarriage, technically called spontaneous abortion, is defined as the loss of a pregnancy before 20 weeks of gestation and occurs in about 15 to 20 percent of all pregnancies.
The actual number, however, is probably higher. Many miscarriages occur very early, going unnoticed before a woman is even aware that she is pregnant.
More than 80 percent of miscarriages occur in the first 12 weeks of pregnancy.
Of these early miscarriages, at least half are thought to be caused by problems with the foetus's chromosomes.
Most of the time, the chromosome problems that cause a miscarriage are not inherited from the parents.
In other words, the chromosome defect in the foetus is not caused by a similar defect in the chromosomes of the mother or father.
Rather, these errors usually happen by chance as the fertilised egg begins to divide.
No foetus at all
A miscarriage caused by a chromosome defect often happens when the foetus would not have been able to survive.
Miscarriage early in pregnancy can occur as many as several weeks after the embryo or foetus has actually died.
And sometimes there was no foetus at all inside the membranes that normally surround the baby.
Other causes of miscarriage may be factors related to the mother's health.
Miscarriage from these causes usually occurs later in pregnancy.
Abnormalities
They include infection, chronic diseases such as diabetes or high blood pressure, and problems with the immune system.
Abnormalities of the uterus or cervix can also cause miscarriage.
Among these problems are cervical incompetence, in which the cervix begins to dilate too early in pregnancy. This nearly always occurs in the second trimester.
Recurrent or repeated miscarriage is defined as three or more miscarriages in a row. You may hear this referred to as habitual abortion.
Success later
The causes of this are much the same as those for a single miscarriage.
Although tests can be done to find the reason for repeated miscarriage, the tests can be costly and the treatment options are somewhat limited.
Even so, many couples go on to have a successful pregnancy later.
If you've had a miscarriage, or are worried about having one, it's also important for you to understand what doesn't cause it.
You are not alone if you have fears about being somehow responsible for the loss of your pregnancy.
Such fears are common among pregnant women, whether or not they have been through this experience.
You are not responsible
Miscarriage is not caused by exercising, having sex, working, or lifting heavy objects.
Nausea and vomiting in early pregnancy, even if severe, will not cause a miscarriage. In fact, there is some evidence that women who have these symptoms are less likely to miscarry.
Finally, it is unlikely that a fall, a blow, or a sudden fright can cause miscarriage.
The foetus is unlikely to be harmed by an injury unless the injury is serious enough to threaten your own life.
Nearly all miscarriages are preceded by the warning sign of vaginal bleeding.
Bleeding is the sign
Up to 25 percent of all pregnant women have bleeding at some point in pregnancy, and of these women, about half will have a miscarriage.
Bleeding that signals a miscarriage may be scant or heavy. It may be constant, or it may come and go.
Bleeding may be followed by cramping abdominal pain and, in some women, lower backache.
Although there may be other reasons for these symptoms, you should contact your doctor if you have any type of bleeding or severe pain in pregnancy.
If you come to your doctor's office with bleeding, the first thing he or she will want to do is to perform a pelvic exam to check whether your cervix has begun to dilate.
If it has, this situation is called threatened abortion a miscarriage will not necessarily happen, but there is a chance that it might.
Examine tissue
Your doctor will also check whether the membranes that surround the foetus have broken.
If they have, and your cervix is dilated, then a miscarriage is certain. This is referred to as inevitable abortion because a miscarriage can't be stopped.
If you have passed tissue, your doctor may suspect that a miscarriage has already occurred.
If the tissue is available, he or she may be able to examine it to see whether it contains any foetal tissue or is actually a clot or a piece of placenta.
An ultrasound exam is often used to try to determine whether there is a live foetus inside the uterus.
Bed rest
With this test, your doctor will try to see the sac that surrounds the foetus or, using a special kind of ultrasonography, check the foetal heartbeat.
If the foetus is not alive but has not been passed out of your body, this is called a missed abortion.
In cases of threatened abortion, bed rest and pain medication may be prescribed until the bleeding or pain has passed.
If bleeding or pain is severe, you may need to be hospitalised.
When the foetal membranes have broken, a miscarriage often occurs soon afterward.
If it doesn't, however, and there is continued bleeding, pain, or a fever, there is a risk of serious infection.
Tissue scraped
In this case, the foetal tissue must be removed from the uterus.
In this procedure, which is done under anesthesia, the cervix is gradually dilated and the tissue is gently scraped or suctioned out.
If you have had a miscarriage or a procedure to empty the uterus, call your doctor right away if you have heavy bleeding, fever, chills, or severe pain. These could be a sign of an infection.
Most women who have had a miscarriage go on to have successful pregnancies later.
Even women with repeated miscarriages (three or more in a row) have a 70 to 85 percent chance of carrying another pregnancy to term.
It is usually advised, however, to wait a while before becoming pregnant again.
Your doctor can advise you about when to attempt pregnancy after a miscarriage. - Staff doctor