Bleeding, common in approximately 10 percent of pregnancies, is most likely to occur during the first trimester and is even more common in twin pregnancies, according to MedlinePlus. The length, color and type of bleeding may help indicate the cause. Bleeding is often not a sign of a medical condition, but monitoring bleeding is critical. Many women who experience bleeding during pregnancy deliver healthy babies.
Implantation Bleeding
Implantation bleeding occurs when the fertilized egg attaches to the uterus. A slight amount of bleeding is sometimes visible several days after conception. The bleeding is minimal and is considered no heavier than light spotting. The blood may appear light pink, dark red or brown, but not bright red. Some women may experience implantation bleeding and mistake it for their period, though the blood flow is much lighter.
Cervical Changes
The cervix begins to soften, and blood flow increases to prepare for pregnancy. These changes may contribute to light bleeding during the early weeks of the first trimester. Bleeding may be present after a pelvic exam or sexual intercourse.
Miscarriage
A common sign of miscarriage is bleeding that lasts about 10 days. Between 10 and 20 percent of pregnancies end in miscarriage, with the majority occurring during the first trimester. Most miscarriages cannot be prevented. A miscarriage is a way for the body to end a pregnancy that is not developing normally. Cramps and passing of tissue are signs associated with a miscarriage. The American Pregnancy Association states a miscarriage is not a sign of an unhealthy mother or that future miscarriages will happen.
Ectopic Pregnancy
The implantation of the fertilized egg outside of the uterus, commonly in the fallopian tubes, causes vaginal bleeding to occur. Sharp pain, cramping and low levels of hCG on a pregnancy test are additional signs of the abnormal condition, commonly referred to as a tubal pregnancy. An ectopic pregnancy occurs in one out of 60 pregnancies and can be life-threatening.
Molar Pregnancy
A molar pregnancy is a rare occurrence that causes vaginal bleeding. Referred to as gestational trophoblastic disease, abnormal tissue begins to grow instead of a fertilized egg. Vaginal bleeding and high levels of hCG are present. An ultrasound reveals a grape-like clusters in the uterus as well as the absence of fetal heart tones.
Placental Abruption or Placenta Previa
Occasionally, medical conditions involving the placenta occur during the second and third trimesters. One percent of women experience placental abruption, or the detachment of the placenta from the uterus during or before labor. The condition causes bleeding and stomach pain. Placental abruption occurs during the final 12 weeks of pregnancy. Women who are older than 35, suffer from sickle cell anemia, have high blood pressure or have a cocaine addiction, may suffer from the condition. Placenta previa, in which the placenta completely covers the cervix, occurs in one out of 200 pregnancies. Painless bleeding occurs, but immediate medical attention is required. Women older than 35 and those who had a previous cesarean section are at higher risk.
Early Labor
Preterm labor is considered labor occurring before the 37th week of pregnancy. Occasionally, blood is seen when the mucosal plug passes from the cervix early. Additional blood may also be seen, indicating the body is going into labor. These signs include uterine contractions, dull aching pain, breaking of the water sack and vaginal discharge.
