A miscarriage is a pregnancy loss before 20 weeks of gestation. Most miscarriages occur in the first trimester of pregnancy. 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. With ovulation (roughly once a month), an egg is released by one of the ovaries and travels the fallopian tube to the uterus. If the egg is fertilized by the male’s sperm, 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.
Miscarriage in early pregnancy is common. About 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. The miscarriage rate also increases with increasing maternal age—for mid-30s, around 30 percent, and at 40 years old, 40-50 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.
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 something is not right. Chromosomal abnormalities, in particular, are common.
In some cases, medical conditions in the mother, such as uncontrolled diabetes or blood clotting disorders, can lead to miscarriage.
Several risk factors can increase the rate of miscarriage.
- Age: Older women are more likely to have a miscarriage than younger women.
- Smoking: Smoking more than 10 cigarettes a day may increase the risk of miscarriage.
- Medical Conditions: Some medical conditions, such as poorly controlled diabetes or poorly controlled thyroid problems, may increase the risk of miscarriage.
Many times, however, miscarriage is a random occurrence without risk factors and is not the result of something you did or did not do.
The most common sign of miscarriage is vaginal bleeding early in pregnancy. Bleeding should always be evaluated. Yet bleeding and discomfort can occur in normal pregnancies. In many cases, bleeding resolves on its own and the pregnancy continues normally without further problems.
Many early miscarriages have no signs or symptoms, and we may not realize something has happened until an ultrasound shows a problem.
Bleeding is never normal in pregnancy and is considered a threatened miscarriage. We often don’t have an explanation for the bleeding yet the pregnancy can progress normally.
In most cases of vaginal bleeding in early pregnancy, we use ultrasound to sort out what is going on and to help determine if the pregnancy is viable, that is, whether it is still developing appropriately.
Ultrasound uses sound waves to visualize the structures inside the uterus. In early pregnancy, the ultrasound exam is often done with a vaginal ultrasound probe. If a pregnancy is too early to be seen on ultrasound, we use HCG blood levels.
With threatened miscarriage, more than one visit and/or ultrasound may be necessary to know for sure what is going on.
We do not intervene unless we are certain a pregnancy is not viable. Sometimes, this cannot be determined with only one visit or ultrasound and you may need to repeat testing in a week, for example. This can be very emotionally trying when we don’t think a pregnancy will be viable, but we are not certain.
When a pregnancy is not viable, 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.
If your body has already passed the pregnancy and bleeding has slowed, nothing may need to be done surgically or medically. Your doctor will instruct you what needs to be done to ensure the miscarriage is complete.
Eventually, your body would start to pass the nonviable pregnancy spontaneously. This can take several weeks for your body to start that process, even though the pregnancy may have stopped developing weeks earlier. Once a woman knows her pregnancy is not viable, she often does not want to wait for the miscarriage to happen spontaneously.
In some cases, medications can be given to stimulate the uterus to contract and pass the pregnancy. This medicine is a pill that can be given by mouth or vaginally, and works over a couple of days. Heavy bleeding and cramping are usually expected with medical treatment.
Surgical Treatment—Suction D&C
The conventional treatment for early miscarriage is a surgical procedure called suction D&C (dilation and curettage). 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.
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. This usually avoids the heavy bleeding and cramping that are typically involved with observation or medical treatment.
Women who have an Rh negative blood type (i.e., A, B, AB, or O negative) may need to be given a drug called Rh(D) immune globulin (RhoGam®). This medicine helps protect future pregnancies against problems that can occur if an Rh negative mother is carrying a baby who is Rh positive.
Following miscarriage, it is recommended to avoid having sex or putting anything into the vagina, such as a douche or tampon, until your doctor says it is ok. This gives time for the cervix to close down to reduce the risk of infection. Women have traditionally been told to wait a specific amount of time before trying to become pregnant again, although several studies have shown no increased risks with a shorter interval. We usually recommend waiting until you have at least one normal menses.
Women experience a range of emotions following miscarriage; there is no right or wrong way to feel, and the loss of a pregnancy can cause significant grief. Sometimes these reactions are strong and long-lasting. An individual experiencing profound sadness or depression following pregnancy loss, especially if it continues for greater than a few weeks, should reach out to a healthcare provider for support. Referral for grief counseling or other treatment also may be helpful.