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Vaginal bleeding during pregnancy can be scary. However, it isn’t always a sign of trouble. Bleeding in the first trimester (weeks one through 12) is common, and most women who experience bleeding during pregnancy go on to deliver healthy babies.
Still, it’s important to take vaginal bleeding during pregnancy seriously. Sometimes vaginal bleeding during pregnancy indicates an impending miscarriage or a condition that needs prompt treatment. By understanding the most common causes of vaginal bleeding during pregnancy, you’ll know what to look for and when to contact your health care provider.
Bleeding when you are pregnant
Bleeding during pregnancy is relatively common, but it can be a dangerous sign, and you should always contact your midwife or GP immediately if it happens to you.
In early pregnancy you might get some perfectly harmless light bleeding, called “spotting”. This is when the developing embryo plants itself in the wall of your womb. This often happens around the time that your first period after conception would have been due.
Causes of bleeding in early pregnancy
During the first 12 weeks of pregnancy, vaginal bleeding can be a sign of miscarriage or ectopic pregnancy. However, many women who bleed at this stage of pregnancy go on to have normal and successful pregnancies.
Miscarriage
If a pregnancy ends before the 24th week of pregnancy, it’s called a miscarriage. Miscarriages are quite common in the first three months of pregnancy and around one in five confirmed pregnancies ends this way.
Many early miscarriages (before 14 weeks) happen because there is something wrong with the baby. There can be other causes of miscarriage, such as hormone or blood clotting problems.
Ectopic pregnancy
Ectopic pregnancies (when a fertilised egg implants outside the womb – for example, in the fallopian tube) can cause bleeding, but are less common than miscarriages.
It’s a dangerous condition, because the fertilised egg can’t develop properly outside the womb. The egg has to be removed this can be through an operation or with medicines. Find out about symptoms of an ectopic pregnancy.
Bleeding in the First Trimester
About 20% of women have some bleeding during the first 12 weeks of pregnancy. Possible causes of first trimester bleeding include:
Implantation bleeding. You may experience some normal spotting within the first six to 12 days after you conceive as the fertilized egg implants itself in the lining of the uterus. Some women don’t realize they are pregnant because they mistake this bleeding for a light period. Usually the bleeding is very light and lasts from a few hours to a few days.
Miscarriage. Because miscarriage is most common during the first 12 weeks of pregnancy, it tends to be one of the biggest concerns with first trimester bleeding. About half of women who bleed in pregnancy eventually miscarry, but that doesn’t necessarily mean that if you’re bleeding you’ve lost the baby, especially if you don’t have any other symptoms.
Other symptoms of miscarriage are strong cramps in the lower abdomen and tissue passing through the vagina.
Ectopic pregnancy . In an ectopic pregnancy, the fertilized embryo implants outside of the uterus, usually in the fallopian tube. If the embryo keeps growing, it can cause the fallopian tube to burst, which can be life-threatening to the mother. Although ectopic pregnancy is potentially dangerous, it only occurs in about 2% of pregnancies.
Other symptoms of ectopic pregnancy are strong cramps or pain in the lower abdomen, and lightheadedness.
Molar pregnancy (also called gestational trophoblastic disease). This is a very rare condition in which abnormal tissue grows inside the uterus instead of a baby. In rare cases, the tissue is cancerous and can spread to other parts of the body.
Other symptoms of molar pregnancy are severe nausea and vomiting, and rapid enlargement of the uterus.
Additional causes of bleeding in early pregnancy include:
- Cervical changes. During pregnancy, extra blood flows to the cervix. Intercourse or a Pap test, which cause contact with the cervix, can trigger bleeding. This type of bleeding isn’t cause for concern.
- Infection. Any infection of the cervix, vagina, or a sexually transmitted infection (such as chlamydia, gonorrhea, or herpes) can cause bleeding in the first trimester.
Bleeding in the Second and Third Trimesters
Abnormal bleeding in late pregnancy may be more serious, because it can signal a problem with the mother or baby. Call your doctor as soon as possible if you experience any bleeding in your second or third trimester.
Possible causes of bleeding in late pregnancy include:
Placenta previa. This condition occurs when the placenta sits low in the uterus and partially or completely covers the opening of the birth canal. Placenta previa is very rare in the late third trimester, occurring in only one in 200 pregnancies. A bleeding placenta previa, which can be painless, is an emergency requiring immediate medical attention.
Placental abruption. In about 1% of pregnancies, the placenta detaches from the wall of the uterus before or during labor and blood pools between the placenta and uterus. Placental abruption can be very dangerous to both the mother and baby.
Other signs and symptoms of placental abruption are abdominal pain, clots from the vagina, tender uterus, and back pain.
Uterine rupture. In rare cases, a scar from a previous C-section can tear open during pregnancy. Uterine rupture can be life-threatening, and requires an emergency C-section.
Other symptoms of uterine rupture are pain and tenderness in the abdomen.
Vasa previa. In this very rare condition, the developing baby’s blood vessels in the umbilical cord or placenta cross the opening to the birth canal. Vasa previa can be very dangerous to the baby because the blood vessels can tear open, causing the baby to bleed severely and lose oxygen.
Other signs of vasa previa include abnormal fetal heart rate and excessive bleeding.
Premature labor. Vaginal bleeding late in pregnancy may just be a sign that your body is getting ready to deliver. A few days or weeks before labor begins, the mucus plug that covers the opening of the uterus will pass out of the vagina, and it will usually have small amounts of blood in it (this is known as “bloody show”). If bleeding and symptoms of labor begin before the 37th week of pregnancy, contact your doctor right away because you might be in preterm labor.
Other symptoms of preterm labor include contractions, vaginal discharge, abdominal pressure, and ache in the lower back.
Additional causes of bleeding in late pregnancy are:
- Injury to the cervix or vagina
- Polyps
- Cancer
