Vaginal bleeding during pregnancy has many causes. Some are serious, and many aren't.

1st trimester

Possible causes of vaginal bleeding during the first trimester include:

• Ectopic pregnancy (in which the fertilized egg implants and grows outside of the uterus, such as in a fallopian tube)
• Implantation bleeding (which occurs about 10 to 14 days after conception when the fertilized egg implants in the lining of the uterus)
• Miscarriage (the spontaneous loss of pregnancy before the 20th week)
• Molar pregnancy (a rare occurrence in which an abnormal fertilized egg develops into abnormal tissue instead of a baby)
• Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix

2nd or 3rd trimester

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

• Incompetent cervix (a premature opening of the cervix, which can lead to preterm birth)
• Miscarriage (before the 20th week) or intrauterine fetal death
• Placental abruption (when the placenta — which supplies nutrients and oxygen to the baby — separates from the wall of the uterus)
• Placenta previa (when the placenta covers the cervix, resulting in severe bleeding during pregnancy)
• Preterm labor (which might result in light bleeding — especially when accompanied by contractions, dull backache or pelvic pressure)
• Problems with the cervix, such as a cervical infection, inflamed cervix or growths on the cervix
• Uterine rupture, a rare but life-threatening occurrence in which the uterus tears open along the scar line from a prior C-section

Normal vaginal bleeding near the end of pregnancy

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

It's important to report any vaginal bleeding during pregnancy to your health care provider. Be prepared to describe how much blood you passed, what it looked like, and whether it included any clots or tissue.

1st trimester

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
• Inform your health care provider if your blood type is Rh negative and you experience bleeding because you might need a medication that prevents your body from making antibodies that may be harmful to your future pregnancies

2nd trimester

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 few hours or is accompanied by abdominal pain, cramping, fever, chills or contractions

3rd trimester

During the third trimester (weeks 25 through 40):

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

In the final weeks of pregnancy, remember that vaginal discharge that is pink or bloody might be a sign of impending labor. Contact your health care provider and confirm that what you are experiencing is indeed bloody show. Occasionally, it might be a sign of a pregnancy complication.