There are many causes of vaginal bleeding in pregnancy. Some result in bleeding early in pregnancy, while others result in bleeding later. 

Usually slight bleeding will stop on its own. Sometimes, though, bleeding may become serious and pose a risk to you or your fetus.  You should call your health care provider or seek medical advice if bleeding occurs. 

Early Pregnancy:

Early Pregnancy

Many pregnant women have vaginal spotting or bleeding in the first 12 weeks of pregnancy. If you are having vaginal bleeding in early pregnancy, your health care provider may perform a pelvic exam. A blood test may be done to measure human chorionic gonadotropin (hCG), a hormone produced during pregnancy. As the pregnancy progresses, hCG levels increase, so you may have more than one test. Ultrasound may be used to find the cause of the bleeding.  Sometimes the cause is not found. If you have bleeding during pregnancy, you may need special care because you have a higher chance of going into labor too early (preterm labor) or having an infant who is born too small.
 
Miscarriage 

Bleeding may be alarming, but it doesn't mean that miscarriage – the loss of a pregnancy in its early stages – is certain. About half of the women who bleed do not have miscarriages. 

If there is a problem with the pregnancy, fetal death usually results in the passage of tissue, and the pregnancy ends.  Miscarriage can occur at any time during the first half of pregnancy, but most occur during the first 12 weeks. At least 20% of all pregnancies end in miscarriage. 

If you have vaginal bleeding, have cramping pain that is felt low in the abdomen, or pass tissue through the vagina, there is a chance of miscarriage. Many women who have vaginal bleeding have little or no cramping. Sometimes the bleeding stops and pregnancy goes on. At other times the bleeding and cramping continue, become stronger, and miscarriage occurs. This pain is usually stronger than menstrual cramps.

If you think you have had a miscarriage, bring any tissue you have passed to the health care provider's office so that it can be examined. If you have had a miscarriage but some tissue remains in the uterus, bleeding often continues. If this happens, the tissue may be removed by a surgical procedure called dilation and curettage (D&C). This may involve dilating, or widening, the cervix (mouth of the uterus) and gently scraping tissue away from the lining of the uterus (the endometrium). The tissue also may be removed by suctioning. This is called suction curettage. 

Most miscarriages cannot be prevented. They are often the body's way of dealing with a pregnancy that was not growing normally.  Usually, having a miscarriage doesn't mean that you can't have more children or that anything is wrong with your health. There is no proof that physical activity or sex during pregnancy cause miscarriage. If you have two or three miscarriages in a row, however, your health care provider may suggest that some tests be performed to look for a possible cause. 

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Another problem that may cause bleeding in early pregnancy is ectopic pregnancy. This is when pregnancy occurs outside the uterus, usually in a fallopian tube. Pelvic pain and vaginal bleeding may result. The tube may burst, and there may be internal bleeding as well. Blood loss may cause weakness, fainting, or even shock. A ruptured ectopic pregnancy requires prompt treatment. 

Ectopic pregnancies are much less common than miscarriages. They occur in about 1 in 60 pregnancies. Women who have had an infection in the tubes (such as pelvic inflammatory disease) have an increased risk. Women who have already had an ectopic pregnancy or have had previous tubal surgery are also at higher risk. 

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Molar Pregnancy

A very rare cause of early bleeding is molar pregnancy. It is also called gestational trophoblastic disease (GTD) or simply a "mole."  It results in the growth of abnormal tissue, rather than an embryo. It may require treatment with suction curettage or with drugs. 

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Late Pregnancy

The causes of bleeding in the second half of pregnancy are different from those in early pregnancy. Common conditions causing minor bleeding include inflammation of or growths on the cervix. 

Bleeding can also be serious and pose a threat to the health of the woman or the fetus. It may require treatment in a hospital.  Heavy vaginal bleeding usually involves a problem with the placenta (afterbirth), the tissue that connects the mother and fetus. The two most common causes are placental abruption and placenta previa.  Preterm labor can also cause vaginal bleeding. 

Placental Abruption

If the placenta becomes detached from the uterine wall before or during labor, vaginal bleeding may occur. Only 1% of pregnant women have this problem, which usually occurs during the last 12 weeks of pregnancy. Abdominal pain often occurs, too, whether or not there is obvious bleeding. When the placenta becomes detached, the fetus can get less oxygen. This can be dangerous.  Women who have already had children, are over 35, have had abruption before, or have sickle cell anemia are at higher risk.  Placental abruption has been linked to: 

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Placenta Previa 

When the placenta lies low in the uterus, it can partly or completely cover the cervix. In the third trimester, this may be linked to vaginal bleeding. This is called placenta previa. It is serious and requires prompt care. 

Placenta previa occurs in only 1 woman in 200. It is more common in women who have had more than one child, who have had a cesarean birth or other surgery on the uterus, or who are carrying twins or triplets. Bleeding is usually painless. 

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Labor

Late in pregnancy, vaginal bleeding may also be a sign of labor.  When the mucus plug that covers the opening of the uterus during pregnancy is passed before or at the start of labor, a small amount of mucus and blood is passed from the cervix. This is called "bloody show."  It is common and not a problem if it happens within a few weeks of your due date. If it happens earlier, you may be going into preterm labor and should talk to your health care provider right away. Other signs of preterm labor include:  

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Taking Action

Contact your health care provider if you have bleeding in late pregnancy. You may need to be admitted to the hospital to find its cause.  Ultrasound may be advised. On occasion, a woman may have to stay in the hospital for several weeks. A woman who is bleeding late in pregnancy may need a blood transfusion. Conditions causing bleeding in late pregnancy pose a risk to both mother and fetus.  They may be serious enough to require early delivery of the baby, sometimes by cesarean birth. 

Finally ...

Many women with bleeding in pregnancy are found to have minor conditions that need no treatment. At other times, bleeding can be the first sign of a serious problem. For this reason, it is very important that bleeding anytime in pregnancy--early or late--be reported to your health care provider. Your health and that of your baby may depend on getting prompt treatment.

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