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.

Possible causes of vaginal bleeding during the first trimester include:

1. Miscarriage — the spontaneous loss of pregnancy before the 20th week
2. Implantation bleeding — which occurs about 10 to 14 days after conception
3. Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix
4. Ectopic pregnancy
5. Molar pregnancy — a rare occurrence in which an abnormal mass — instead of a baby — forms inside the uterus after fertilization

Possible causes of vaginal bleeding during the second or third trimester include:

1. Miscarriage (before the 20th week) or intrauterine fetal death
2. Placental abruption
3. Cervical cancer
4. Incompetent cervix — Premature opening of the cervix — which can lead to preterm birth
5. Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix
6. Preterm labor — which might result in light bleeding — especially when accompanied by contractions, dull backache or pelvic pressure
7. Uterine rupture, a rare but life-threatening occurrence in which the uterus tears open along the scar line from a prior C-section

Light bleeding, often mixed with mucous, near the end of pregnancy could be a sign that labor is starting. Vaginal discharge that is pink or bloody is known as the bloody show.

Causes shown here are commonly associated with this symptom. Work with your doctor or other health care professional for an accurate diagnosis.

Source: mayoclinic.org

During the first trimester (weeks one through 12):

• Tell your health care provider at your next prenatal visit if you have spotting or light vaginal bleeding that goes away within a day
• Contact your health care provider within 24 hours if you have any amount of vaginal bleeding that lasts longer than a day
• Contact your health care provider immediately if you have moderate to heavy vaginal bleeding, pass tissue from your vagina, or experience any amount of vaginal bleeding accompanied by abdominal pain, cramping, fever or chills

During the second trimester (weeks 13 through 24):

• Contact your health care provider the same day if you have light vaginal bleeding that goes away within a few hours
• Contact your health care provider immediately if you have any amount of vaginal bleeding that lasts longer than a day or is accompanied by abdominal pain, cramping, fever, chills or contractions

During the third trimester (weeks 25 through 40):

• Contact your health care provider immediately if you have any amount of vaginal bleeding before 37 weeks or vaginal bleeding accompanied by abdominal pain.

In the final weeks of pregnancy, remember that vaginal discharge that is pink or bloody (bloody show) is a normal sign of impending labor.

Source: mayoclinic.org