Vaginal bleeding during pregnancy: What causes it, and what should you do?

If you're pregnant, even a small amount of vaginal bleeding can be scary. Sometimes, bleeding does signal trouble — but not always. In fact, many pregnant women experience light vaginal bleeding at some point during pregnancy, particularly during the first trimester. Often, such bleeding is the result of a normal event during pregnancy, such as the embryo's implantation in the uterine lining a little over a week after conception.

Bleeding shouldn't throw you into a panic. At the same time, you should always take bleeding seriously if you're pregnant, monitoring it closely and taking note of related symptoms, such as cramping. By understanding the most common causes of bleeding during pregnancy, you'll know what to look for and when to call your health care provider.

Bleeding in the first trimester

Many women have spotting or bleeding in the first 12 weeks of pregnancy. In most cases, women who experience light bleeding in the first trimester go on to have normal, successful pregnancies. There are no hard and fast rules about what amount of bleeding — or which additional signs or symptoms — indicate that there is a problem, but these things can be helpful in deciding when further investigation is in order. So, you'll want to describe the bleeding and any other signs or symptoms to your health care provider.

What causes it?
Common causes of early pregnancy bleeding include:

• Implantation bleeding. You may notice a small amount of spotting or bleeding very early in pregnancy, about 10 to 14 days after fertilization. Known as implantation bleeding, it happens when the fertilized egg attaches to the lining of your uterus. It's usually earlier, spottier and lighter in color than a normal menstrual period, and it doesn't last long. Some women actually mistake this light bleeding for a period and don't realize they're pregnant.
• Cervical changes. When you're pregnant, there's an increase in the blood supply and blood flow to your cervix. So you may experience light spotting after contact to this area, such as after sexual intercourse or a pelvic exam. This type of light bleeding in pregnancy is usually normal.
• Miscarriage. Bleeding in the first trimester can be a sign of miscarriage. Miscarriage occurs in 15 percent to 20 percent of known pregnancies, most often during the first 12 weeks. However, bleeding doesn't necessarily mean you're having a miscarriage — at least half the women who bleed in the first trimester don't have miscarriages.
• Ectopic pregnancy. Also called tubal pregnancy, this condition occurs when the embryo implants somewhere outside the uterus, usually in a fallopian tube. It's much less common than miscarriage. However, an embryo implanted outside the uterus can't develop into a normal baby, and it can cause serious internal bleeding. Ectopic pregnancies must be removed to save the life of the mother. Other symptoms of ectopic pregnancy include abdominal pain, which is usually worse on one side, lightheadedness and an urge to have a bowel movement.
• Molar pregnancy. In this rare condition, an abnormal mass — instead of a baby — forms inside the uterus after fertilization. Bleeding is the most common symptom of a molar pregnancy, but this is an uncommon cause of bleeding in the first trimester.
• Other reasons not related to pregnancy. Spotting or vaginal bleeding can be caused by trauma or tears to the vaginal wall. Some cervical infections also may cause bleeding in early pregnancy.

When to call your health care provider and what to expect

If you have slight spotting that goes away within a day, tell your health care provider at your next visit. If you have any spotting or bleeding that lasts more than a day, call your health care provider within the next 24 hours. Contact him or her immediately if you have:

• Moderate to heavy bleeding
• Any amount of bleeding accompanied by pain, cramping, fever or chills
• Passing of tissue from the vagina

Your health care provider will likely ask you lots of questions and perform a physical exam, including a pelvic exam. Depending on the seriousness of your symptoms, your health care provider may order lab tests or an ultrasound to assess the status of your pregnancy. These tests can detect the presence of an embryo that has a heartbeat and determine if it's growing according to schedule. Treatment for spotting or vaginal bleeding in early pregnancy depends on the cause.

Bleeding in the second or third trimester

Common conditions, such as cervical growths or inflammation, can cause minor bleeding in the second half of pregnancy. But bleeding can also pose a threat to your health or the health of your baby. The most common cause of heavy vaginal bleeding in late pregnancy is a problem with the placenta, such as placenta previa or placental abruption.

What causes it?
Bleeding in the second trimester may come from:

• Miscarriage. Although miscarriage is less common in the second trimester than the first, a risk still exists.
• Problems with your cervix. A cervical infection, inflamed cervix or growths on your cervix can cause vaginal bleeding in the second or third trimesters. Occasionally, light bleeding from the cervix may be a sign of cervical incompetence — a condition in which the cervix opens spontaneously, leading to preterm delivery. This condition occurs most frequently between 18 and 23 weeks of pregnancy and requires prompt medical care.
• Placenta previa. Moderate to heavy bleeding in the late second or third trimester may indicate placenta previa — a problem in which the placenta lies too low in the uterus and partly or completely covers the opening to the birth canal. The main sign of placenta previa is painless bright red vaginal bleeding. The bleeding may stop on its own at some point, but it nearly always recurs days or weeks later. This is a serious condition that requires immediate care. It occurs in one in every 200 pregnant women, most often in the third trimester.
• Placental abruption. In this condition — which affects only 1 percent to 2 percent of pregnant women — the placenta begins to separate from the inner wall of the uterus before birth, causing bleeding within the uterus. The bleeding from placental abruption may be scant, heavy or somewhere in between, but it's usually accompanied by abdominal pain. This condition usually occurs in the last 12 weeks of pregnancy.
• Uterine rupture. In women who have had a previous Caesarean birth, a disruption of the surgical scar in the uterus is a rare but dangerous cause of vaginal bleeding, intense abdominal pain and abdominal tenderness. It causes the baby to be partially or completely expelled into the abdomen.
• Preterm labor. Light bleeding from 20 to 37 weeks may indicate preterm labor, especially when accompanied by pelvic or abdominal pressure, dull backache, abdominal cramps or uterine contractions. If you have any signs or symptoms of labor before 36 weeks, call your health care provider right away.
• A sign of labor (bloody show). During pregnancy, a thick plug of mucus seals the opening of the cervix to prevent bacteria and other germs from entering the uterus. As your body prepares for labor, the cervix begins to thin out and relax, and the mucous plug is dislodged. When this happens, you may notice a thick or stringy discharge that may be tinged with blood. Known as the bloody show, this is a normal sign of labor that may occur up to a week or two before delivery day.

When to call your health care provider and what to expect next

Call your health care provider if you have any spotting or bleeding in the second or third trimester, and expect to go to the hospital or doctor's office to determine the cause. Call your health care provider immediately if you have any amount of bleeding accompanied by:

• Pain
• Cramping
• Fever
• Chills
• Contractions

Many times, there will be an explanation for the bleeding that isn't threatening to you or your baby, but it's not possible for your health care provider to come to that conclusion over the phone.

He or she will likely suggest an ultrasound to check for placenta previa. If placenta previa is ruled out, you'll have a vaginal exam to see if your cervix is dilated. You may also be hooked up to monitors that can detect contractions and track your baby's heart rate.

If you've lost a significant amount of blood, you may need intravenous fluids or blood transfusion. Plus, doctors will closely watch your baby for signs of distress.

Treatment for vaginal bleeding in late pregnancy depends on the cause of the bleeding, your health and the gestational age of your baby. Treatment may include bed rest, medications or even urgent delivery of your baby.

Details are key to diagnosis

Although you may be embarrassed to talk about vaginal bleeding, your health care provider has to know all the details so that he or she can identify the cause of the bleeding and the necessary next steps. Don't be shy about explaining your symptoms — including how much blood you passed, what it looked like, and whether it included any clots or tissue. If you use pads to soak up the blood, keep track of how many. All this information can help your health care provider decide if your spotting or bleeding is a normal part of pregnancy or something more serious. Then, the two of you can decide what to do next.

Related

Preeclampsia
Premature birth
Ectopic pregnancy
Placental abruption
Placenta previa
Molar pregnancy: Will it happen again?