A miscarriage is a failed intrauterine pregnancy that ends before 20 weeks from the last menstrual period. A brief review of the events of early pregnancy will help in the understanding of miscarriage.
A woman's reproductive system includes the uterus (including the cervix), two ovaries, two fallopian tubes, and the vagina. The fallopian tubes are a pair of hollowed tubes that run from each side of the uterus to the ovaries (figure 1). Once a month, an egg is released by one of the ovaries and travels down the fallopian tube. If the egg is fertilized in the tube by the male's sperm, pregnancy begins.
Once the egg and sperm join, they rapidly develop new cells. This bundle of cells, called the embryo, normally implants on the inner wall of the uterus. Once implanted, the embryo continues to grow inside a sac of amniotic fluid, sometimes called the "bag of water." After several weeks, the embryo is called a fetus.
Miscarriage in early pregnancy is common. Studies show that about 8 to 20 percent of women who know they are pregnant have a miscarriage some time before 20 weeks of pregnancy; 80 percent of these occur in the first 12 weeks . But the actual rate of miscarriage is even higher since many women have very early miscarriages without ever realizing that they are pregnant. One study that followed women's hormone levels every day to detect very early pregnancy found a total miscarriage rate of 31 percent .
Many factors can lead to miscarriage, and it is difficult to say with certainty what causes a particular miscarriage to occur. One or more problems with the pregnancy can be found in a significant percentage of early miscarriages.
As an example, in one-third of miscarriages occurring before 8 weeks, there is a pregnancy sac but no embryo inside. This means the egg was fertilized and the cells began to divide, but an embryo did not develop. In other cases, the embryo develops but it is abnormal. Chromosomal abnormalities, in particular, are common. One study found that of more than 8000 miscarriages, 41 percent had chromosomal abnormalities.
In some cases, medical conditions in the mother, such as uncontrolled diabetes, or structural problems in the reproductive tract, such as uterine fibroids, can lead to miscarriage. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes mellitus (Beyond the Basics)" and "Patient information: Uterine fibroids (Beyond the Basics)".)
MISCARRIAGE RISK FACTORS
Several risk factors can increase the rate of miscarriage.
●Age — Older women are more likely to have a miscarriage than younger women.
●Previous miscarriage — Having a miscarriage in the past may increase the risk for a future miscarriage.
●Smoking — Smoking more than 10 cigarettes a day increases the risk of miscarriage.
●Alcohol — No amount of alcohol is known to be safe during pregnancy because it can cause health problems for the baby. Drinking alcohol also increases the risk of miscarriage.
●Fever — Pregnant women who develop fevers of 100ºF (37.8ºC) or more appear to have an increased risk of miscarriage.
●Trauma — Trauma to the uterus can increase the risk of miscarriage. This includes some forms of prenatal testing, such as amniocentesis or chorionic villus sampling. The effect of minor trauma to the mother’s abdomen is unknown, because during early pregnancy the uterus is generally protected from blunt trauma. (See "Patient information: Amniocentesis (Beyond the Basics)" and "Patient information: Chorionic villus sampling (Beyond the Basics)".)
●Other causes — Women who are exposed to certain substances or conditions may have an increased risk of congenital abnormalities and miscarriage. This includes exposure to certain infections, medications, radiation, physical stresses, and environmental chemicals.
It does not appear the caffeine intake increases the risk of miscarriage, with the possible exception of intake of very high levels (ie, 1000 mg, or 10 cups of coffee, over 8 to 10 hours).
MISCARRIAGE SIGNS AND SYMPTOMS
The most common signs of miscarriage are vaginal bleeding and abdominal pain early in pregnancy. These problems should always be evaluated by a clinician. However, bleeding and discomfort can occur in normal pregnancies. In many cases, bleeding resolves on its own and the pregnancy continues normally without further problems.
Healthcare providers use the following terms to describe the various types of miscarriage.
Threatened miscarriage — A woman who has vaginal bleeding early in pregnancy but no other signs of problems is said to have a threatened miscarriage. The cervix, or opening to the uterus, is closed, and the uterus is the correct size for the woman's particular stage of pregnancy. If the pregnancy is far enough along, a fetal heart beat may be detected. In many women with threatened miscarriage, the bleeding subsides and the pregnancy continues to term. In others, the bleeding becomes heavier and miscarriage occurs.
Inevitable miscarriage — Inevitable miscarriage means that a miscarriage cannot be avoided. The cervix is open, bleeding is heavy or increasing, and abdominal cramping is present.
Incomplete miscarriage — An incomplete miscarriage means that the woman has passed much of the pregnancy tissue, but some remains in the uterus. Typically, the fetus has been passed, but bits of the placenta remain. The cervix remains open, and bleeding may be heavy.
Complete miscarriage — A woman who passes all of the pregnancy tissue is said to have had a complete miscarriage. This is common in miscarriages that occur before 12 weeks of pregnancy. After the miscarriage there is a period of bleeding and cramping, which resolves without treatment. On examination, the clinician typically finds that the cervix is closed, and there is no sign of a pregnancy sac in the uterus. An ultrasound examination may be performed to confirm the diagnosis.
Septic miscarriage — Some women who have miscarriage develop an infection in the uterus. This is known as a septic miscarriage. Symptoms include fever, chills, flu-like aches, abdominal pain, vaginal bleeding, and vaginal discharge, which may be thick and may have a foul odor.
In some cases, miscarriage can be diagnosed based upon the woman's symptoms and the physical exam. As an example, with inevitable miscarriage, the cervix is open and pregnancy tissue may be seen in the cervix.
However, in many cases of vaginal bleeding in early pregnancy, ultrasound is used to establish a diagnosis, and/or to help determine if the pregnancy is "viable", that is, whether it is capable of progressing to term. In addition, it is important to make sure that the pregnancy is in the uterus. Pregnancies outside the uterus (eg, in the fallopian tube) need immediate evaluation and care and can be life threatening. (See "Patient information: Ectopic (tubal) pregnancy (Beyond the Basics)".)
Ultrasound — Ultrasound uses sound waves to visualize the structures inside the uterus. In early pregnancy, the ultrasound exam is often done through the vagina. In a woman who has had a complete miscarriage, no pregnancy sac or embryo will be seen on ultrasound. In other women, a pregnancy sac will be seen but it will be abnormal or an embryo will not be present, indicating that the pregnancy is not viable.
If an embryo is present, its size is measured and compared to the size that is expected at the woman's stage of pregnancy. The sac and other materials surrounding the embryo are also examined to look for abnormalities in these structures.
Fetal heart beat — At about 6 weeks after the last menstrual period, the motion of the fetal heart should be visible on ultrasound. If the pregnancy has progressed to the stage where a heart beat should be present, the failure to detect a heart beat during an ultrasound exam indicates that the pregnancy has likely ended.
On the other hand, the presence of a fetal heart beat (in the absence of other abnormalities in the pregnancy) indicates the pregnancy may still be viable and that miscarriage may not occur.
Doctors will also evaluate the rate of the fetal heart. A fetal heart beat that is less than 100 to 120 beats per minute can indicate that a miscarriage is likely.
MISCARRIAGE TREATMENT OPTIONS
Unfortunately, there is no way to stop most miscarriages once they have started. When a miscarriage is inevitable or is already occurring , several options are available, depending upon the stage of the miscarriage, the condition of the mother, and other factors. The three main options are: observation, medical treatment, or surgical treatment.
Observation — Some women having a miscarriage require little treatment. Most women with complete miscarriage fall into this group. In addition, women who miscarry at less than 12 weeks of pregnancy and have stable vital signs (blood pressure, pulse) and no signs of infection can often be managed without medical or surgical treatment.
In time, the contents of the uterus will pass, usually within two weeks, although sometimes as long as 3 to 4 weeks later. Once the contents have been passed, an ultrasound is done to ensure that the miscarriage is complete.
Medical treatment — In some cases, medications can be given to stimulate the uterus to pass the pregnancy tissue. The medicine can be given by mouth or vaginally, and works over several days.
Surgical treatment — The conventional treatment for early miscarriage is a surgical procedure called dilation and curettage, or D&C. The cervix (the opening to the uterus) is dilated, and an instrument is inserted that uses suction and/or a gentle scraping motion to remove the contents of the uterus. (See "Patient information: Dilation and curettage (D and C) (Beyond the Basics)".)
D&C is generally recommended for women who do not want to wait for spontaneous passage of the pregnancy, and in women with heavy bleeding or infection.
Following miscarriage, women are advised to avoid having sex or putting anything into the vagina, such as a douche or tampon, for two weeks. Women have traditionally been told to wait two to three months before trying to become pregnant again, although several studies have shown no increased risks with a shorter interval. Any type of birth control, including an intrauterine device, may be started immediately. (See "Patient information: Birth control; which method is right for me? (Beyond the Basics)".)
Medications may be given to help decrease bleeding and reduce the risk of infection. In addition, women who have an Rh negative blood type (ie, A, B, AB, or O negative) need to be given a drug called Rh(D) immune globulin (RhoGam). This medicine helps protect future fetuses against problems that can occur if an Rh negative mother is carrying a baby who is Rh positive.
Emotional health — Women experience a range of emotions following miscarriage; there is no right or wrong way to feel. The loss of a pregnancy can cause significant grief. Sometimes these reactions are strong and long-lasting. A woman should let her healthcare provider know if she is feeling profound sadness or depression following pregnancy loss, especially if it continues for greater than several weeks. Referral for grief counseling or other treatment may be helpful. (See "Patient information: Depression in adults (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Miscarriage (The Basics)
Patient information: Dilation and curettage (D and C) (The Basics)
Patient information: Threatened miscarriage (The Basics)
Patient information: Repeated miscarriage (The Basics)
Patient information: Hyperthyroidism (overactive thyroid) and pregnancy (The Basics)
Patient information: Pregnancy in Rh-negative women (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Care during pregnancy for women with type 1 or 2 diabetes mellitus (Beyond the Basics)
Patient information: Uterine fibroids (Beyond the Basics)
Patient information: Amniocentesis (Beyond the Basics)
Patient information: Chorionic villus sampling (Beyond the Basics)
Patient information: Dilation and curettage (D and C) (Beyond the Basics)
Patient information: Birth control; which method is right for me? (Beyond the Basics)
Patient information: Depression in adults (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Definition and etiology of recurrent pregnancy loss
Effect of advanced age on fertility and pregnancy in women
Evaluation of couples with recurrent pregnancy loss
Management of couples with recurrent pregnancy loss
Spontaneous abortion: Management
Spontaneous abortion: Risk factors, etiology, clinical manifestations, and diagnostic evaluation
Pregnancy in women with antiphospholipid syndrome
The following organizations also provide reliable health information.
●National Library of Medicine
(www.nlm.nih.gov/medlineplus/pregnancyloss.html, available in Spanish)
●The March of Dimes
●Pregnancy & Infant Loss Support, Inc.