A miscarriage (in medical terms, a spontaneous abortion) is the expulsion from the uterus of the fetus and placenta before the beginning of the 20th week of pregnancy. At that point, the fetus is not developed enough to survive outside the uterus on its own. (After the 20th week of pregnancy and before the 36th week, expulsion of the fetus and placenta is considered premature delivery.) Most miscarriages occur within the first 14 weeks of pregnancy.
It is impossible to know how many miscarriages occur during the first month of pregnancy, before many women may even realize they are pregnant. The only indication may be a slightly late menstrual period with a heavier than normal flow. However, about 15 percent of known pregnancies end in miscarriage.
There are different categories of miscarriages.
- One of every five pregnant women experiences a threatened miscarriage when she bleeds vaginally during the first three months. Although it may indicate that a spontaneous abortion will eventually occur, it is often no more than a threat, and the pregnancy continues normally.
- An inevitable miscarriage occurs when the woman begins to bleed and the cervix dilates; it is then only a matter of time before the contents of the uterus are expelled.
- A missed miscarriage occurs when the fetus dies and the placenta stops growing; this may occur several days to weeks before the contents of the uterus are naturally expelled.
- An incomplete miscarriage occurs when only part of the uterine contents has been expelled.
- A complete miscarriage occurs when all of the uterine contents have been naturally expelled.
The reason a miscarriage occurs is not always known, but in many cases it is believed that a fetus aborts because it is not developing normally. Several factors can contribute to abnormal fetal development, including the following:
- Abnormalities in the father's sperm
- Abnormalities in the egg
- Disease in the mother, most notably rubella (German measles), severe heart or kidney disease, diabetes, or thyroid disease
- Abnormalities in the uterus
- The mother's use of certain drugs
- The mother's exposure to toxic substances or certain environmental pollutants
Contrary to popular belief, severe emotional trauma or stress, automobile accidents, and simply falling rarely, if ever, cause miscarriage.
The expulsion of the fetus because of an abnormality is thought to be a chance event, usually not due to a defect in either parent. Of women who miscarry once, most (80 percent) have a successful subsequent pregnancy.
Although it is uncommon, some women miscarry three or more times in a row; they are called habitual aborters. When this occurs, the physician conducts a thorough evaluation of both the woman and her partner to determine the cause, if any. Frequently, a chromosome abnormality in one parent or an abnormality of the uterus is found. If an abnormality of the uterus is the cause of miscarriage, corrective surgery may be done, and a successful pregnancy often results. If the cause of miscarriage is a chromosome abnormality in either parent, the problem cannot be corrected.
Miscarriage is rarely life-threatening for the mother, especially if diagnosed and treated promptly. Though blood loss may occur, it is generally not enough to cause serious problems.
The symptoms of miscarriage are vaginal bleeding (from a few drops to a heavy flow) and uterine cramps (either dull and constant or sharp and intermittent) felt in the lower part of the abdomen or back. The bleeding can start suddenly or follow a brownish discharge. A solid clot of blood or tissue may pass from the vagina. If possible, this should be saved for the doctor, who may be able to examine it and determine the cause of the bleeding.
A pregnant woman who starts bleeding or experiences abdominal pain should contact her doctor immediately.
If a threatened miscarriage is diagnosed, the doctor generally directs the woman to rest in bed, avoid heavy lifting and pushing, and abstain from sexual intercourse. Though it is traditional for doctors to give this advice, many physicians feel little can be done to stop or avert a miscarriage.
After an inevitable, incomplete, or missed miscarriage, any tissue remaining in the uterus causes continued bleeding and possibly infection. To remove any retained tissue, the doctor performs a D & C (dilatation and curettage). This is a surgical procedure in which the cervix is dilated by means of tapered metal dilators, and the contents of the uterus are scraped out with suction and a sharp instrument called a curette.
If you are carrying more than one fetus, you also might not carry to full term. On the next page find out why multiple births increase the liklihood of premature labor.