The National Institutes of Health suggests that up to 10 percent of women experience vaginal bleeding at some point during pregnancy. The bleeding most often occurs during the first trimester. Bleeding in the first half of pregnancy can often be identified as something perfectly normal but there are a few more serious causes. Women should always consult a medical professional when bleeding occurs in pregnancy.
Miscarriage
Bleeding during the first three months of pregnancy can indicate a miscarriage. The National Institutes of Health suggests that bleeding that begins sometime after the third month is not likely to be a miscarriage. Other signs of miscarriage include sharp pains in the abdomen, cramping and the passing of tissues from the vagina.
Implantation
During the early weeks of pregnancy, such as the fourth through the sixth week, implantation occurs. This is where the fertilized egg attaches to the uterine lining. This can cause mild cramping and some spotting. Some women attribute this to an upcoming period when pregnancy has not yet been identified. The vaginal bleeding with implantation is often very light for just a few hours or a few days.
Ectopic Pregnancy
An ectopic pregnancy is one that can't be carried to term. The fertilized egg implants somewhere outside the uterus, most often to one of the fallopian tubes. This abnormal pregnancy is very serious because it can lead to the fallopian tube rupturing, the National Institutes of Health notes. The symptoms of an ectopic pregnancy include vaginal bleeding, mild cramping on one side of the pelvis, nausea and pain the lower abdomen. If the pregnancy ruptures it can lead to fainting, feeling faint, pain in the shoulder area or the sudden onset of severe pain in the lower abdomen. Symptoms of shock are the first signs of an ectopic pregnancy in about 20 percent of cases. Such symptoms include chest pain, confusion, dizziness, pale skin, clammy skin, profuse sweating, fainting, shallow breathing or bluish lips and fingernails.
Molar Pregnancy
The American Pregnancy Association explains that a molar pregnancy can cause bleeding during the first half of the pregnancy but this condition is extremely rare. A molar pregnancy occurs when an abnormal growth exists in the uterus instead of an actual embryo. The levels of human chorionic gonadotropin, or hCG, will be abnormally high in this situation, which is why pregnancy tests will be positive. In addition to vaginal bleeding, an ultrasound or Doppler device may not reveal a fetal heart beat.
Infection
Any type of vaginal infection can cause vaginal bleeding. Some infections can also cause cramping and a foul odor. Treatment is important, even for common yeast infections, to prevent pregnancy complications.
Intercourse
The cervix is generally tender and sensitive during pregnancy, according to the American Pregnancy Association. This can cause bleeding following intercourse.
