It is the most common cause of early pregnancy bleeding and is associated only with heavy (versus light) bleeding. However, patients typically remain hemodynamically stable. Threatened early pregnancy loss, often considered a type of early pregnancy loss, refers vaginal bleeding in the presence of an intrauterine pregnancy and a closed cervix. The presence of fetal heart rate largely determines whether the pregnancy will progress to a viable outcome. Ectopic pregnancy refers to a pregnancy outside the uterus, commonly in the fallopian tube. It is a less common but more serious cause of early pregnancy bleeding. Ectopic pregnancies can rupture, leading to internal bleeding that can be fatal if untreated. Implantation bleeding involves a small amount of bleeding that may occur 10 to 14 days after implantation of the fertilized egg. However, there is little evidence to support the existence of such bleeding. Chorionic hematoma is the pooling of blood (hematoma) between the chorion, a membrane surrounding the embryo, and the uterine wall. It occurs in about 3.1% of all pregnancies and is the most common cause of first trimester bleeding. Gestational trophoblastic neoplasia, which refers to pregnancy-related tumors that be either cancerous or non-cancerous. This cause is extremely rare with non-cancerous gestational trophoblastic neoplasia found in 23 to 1,299 cases per 100,000 pregnancies and cancerous forms with a 10-fold lower incidence.Obstetric causes of second/third trimester bleeding include the following:

Bloody show refers to the passage of a small amount of blood or blood-tinged mucus resulting from labor or cervical weakness.
The parental source may be a disruption in the vessels of the decidua or a lesion in the cervix or vagina. In the earlier stages of pregnancy, the cervix can be vulnerable to bleeding as new blood vessels are being grown. Vasa praevia is a rare condition that can result in bleeding from the fetoplacental circulation. Vasa praevia happens most often when the umbilical cord grows in a way that it directly enters the membrane, and therefore blood vessels that are unprotected by the umbilical cord or placental tissue can rupture and lead to bleeding. Another common source of bleeding can be due to abnormal development of the embryo. The most common early fetal abnormality is abnormal number of chromosomes causing loss of the pregnancy and bleeding. Diagnostic approach
The initial assessment of vaginal bleeding in early pregnancy must first consider hemodynamic stability and the degree of pain or bleeding. A hemodynamically unstable patient would necessitate an immediate transfer to the emergency department . It is important to recognize that patients may suffer significant blood loss before any signs of hemodynamic instability are evident.The initial evaluation of early pregnancy bleeding involves a history and physical examination. The relevant history includes determining the gestational age of fetus and characterizing the bleeding. Bleeding that is at least as heavy as menstrual bleeding or associated with clots, tissue, lightheadedness, or pelvic discomfort is associated with increased risks of ectopic pregnancy and spontaneous abortion.